FROM: Roberts: Clinical Procedures in Emergency Medicine, 3rd ed., Copyright © 1998 W. B. Saunders Company
Chapter 40 - Incision and Drainage
Cutaneous abscesses are among the soft tissue infections most frequently encountered in the emergency department (ED). Approximately 1 to 2% of patients presenting to the ED receive care for cutaneous abscesses.   In contrast with most bacterial diseases, which are usually described in terms of their etiologic agent, cutaneous abscesses are best described in terms of their location. There has been little systematic investigation into the bacteriology of simple cutaneous abscesses, and there have been few new recommendations for improved management over the years. The probable reason for this lack of scientific rigor is the predictable and striking clinical recovery once a mature abscess is incised and drained. The exact reasons for this amelioration of local and constitutional symptoms are unknown; however, it is clear that the exact bacteriology of cutaneous abscesses, while academically interesting, is essentially inconsequential to the final outcome in most cases. 
Although most incision-and-drainage procedures are performed for decompression of purulent collections, drainage of sterile hematomas or seromas may be required in the ED. In general, the same principles used for formal drainage of pus in the soft tissues apply to drainage of a sterile fluid collection, and hence one can directly apply the principles of this chapter to the drainage of sterile fluids. In addition, when a sterile fluid collection is drained, the operator has the option of primarily closing the incision site following wound irrigation (see Chapter 37 for wound closure techniques). Drainage of a soft tissue hematoma is generally best postponed several days following an initial injury to permit hemostasis and to minimize the risk of hematoma reaccumulation following drainage. The procedure is generally reserved for those soft tissue hematomas that are large and painful (secondary to tissue distention) and are expected to either resolve slowly or result in soft tissue deformity if not drained. Drainage of a subungual hematoma represents a special case of hematoma drainage and is discussed in detail later in this chapter.
ABSCESS ETIOLOGY AND PATHOGENESIS
Localized pyogenic infections may develop in any region of the body and usually are initiated by a breakdown in the normal epidermal defense mechanisms, with subsequent tissue invasion by normal resident flora. Thus, an abscess is likely to be caused by the flora that are indigenous to that area. An exception is direct inoculation of extraneous organisms, such as infections that follow mammalian bites.
Staphylococcal strains, which are normally found on the skin, produce rapid necrosis, early suppuration, and localized infections with large amounts of creamy yellow pus. This is the presentation of a typical abscess. Group A beta-hemolytic streptococcal infections, on the other hand, tend to spread through tissues, causing a more generalized infection characterized by erythema and edema, a serous exudate, and little or no necrosis. This is the presentation of a typical cellulitis. Anaerobic bacteria proliferate in the oral and perineal regions; produce necrosis with profuse brownish, foul-smelling pus  ; and may cause both abscess and cellulitis.
Normal skin is extremely resistant to bacterial invasion, and few organisms are capable of penetrating the intact epidermis. In the normal host with intact skin, the topical application of even very high concentrations of pathogenic bacteria does not result in infection. The requirements for infection include a high concentration of pathogenic organisms, such as occurs in the hair follicles and their adnexa; occlusion, which prevents desquamation and normal drainage, creating a moist environment; adequate nutrients; and trauma to the corneal layer, which allows organisms to penetrate.  Trauma may be the result of abrasions, hematoma, injection of chemical irritants, incision, or occlusive dressings that cause maceration of the skin. Foreign bodies can also potentiate these infections and decrease the number of bacteria necessary for infection. An example of this is the ubiquitous suture abscess, which frequently develops in otherwise clean wounds closed with suture material.
When favorable factors are present, normal flora of cutaneous areas can then colonize and infect the skin. The bodily area involved depends primarily on host factors. In persons performing manual labor, the arms and the hands are infected most frequently. In women, the axilla and submammary regions are frequently infected because of minor trauma from shaving and garments and because of the abundance of bacteria in these areas. IV drug users may develop infections anywhere on the body, although the upper extremities are most commonly affected.   Deep soft tissue abscesses have also been described following attempts at access to the deep venous structures in addicts who have exhausted all peripheral venous access sites.  In addition, areas with compromised blood supply will be more prone to infection, because normal host cell-mediated immunity is not as available.  Septic emboli from endocarditis may cause abscess formation by bacteremic migration of infected material into subcutaneous (SQ) tissue.
Infections in the soft tissue often begin as a cellulitis. Some organisms cause necrosis, liquefaction, and accumulation of leukocytes and debris, followed by loculation and walling off of pus, all of which result in the formation of 1 or more abscesses. There may be involvement of the lymph tissues, producing lymphangitis and subsequent bacteremia. As the process progresses, the area of liquefaction increases until it "points" and eventually ruptures into the area of least resistance. This may be toward the skin or the mucous membrane, into surrounding tissue, or into a body cavity. If the abscess is particularly deep-seated, spontaneous drainage may occur, with persistence of a fistulous tract and the formation of a chronic draining sinus. This development, or the recurrence of an abscess that has been previously drained, should always suggest the possibility of osteomyelitis, a retained foreign body, or the presence of unusual organisms such as Mycobacterium or Actinomyces.
Bacteriology of Cutaneous Abscesses
Meislin and coworkers  cultured abscesses in 135 patients, and their report typifies the bacteriology and natural history of cutaneous abscesses. Their patients received simple incision and drainage, and all subjects were followed as outpatients. Both aerobic and anaerobic cultures were taken. Most (96%) cultures were positive for bacteria (Table 40-1) (Table Not Available) .
In this series predominantly mixed aerobic bacteria were isolated in abscesses of the trunk, axilla, extremities, and the hand. In pure cultures, Staphylococcus aureus was found in 72% of cases. One third of the cultures from the perianal region contained only anaerobes. Mixed cultures of both aerobic and anaerobic bacteria were obtained from all sites of the body, but there was a 67% incidence of such mixed cultures from the perirectal area. Commonly isolated anaerobes included various Bacteroides spp, peptococci, peptostreptococci, Clostridium spp, Lactobacillus spp, and Fusobacterium spp.
Bacteria from abscesses in areas remote from the rectum were generally aerobic strains and were primarily indigenous microflora of the skin. S. aureus was the most prevalent aerobic organism; it was isolated in 24% of all abscesses.
Gram-negative aerobes were isolated infrequently from cutaneous abscesses. Escherichia coli, Neisseria gonorrhoeae, and Pseudomonas spp were rarely found. The most commonly isolated gram-negative organism was Proteus mirabilis. This organism was found almost exclusively in the axilla, and its presence may be related to the use of underarm deodorants. 
Brook and Finegold  studied the bacteriology of cutaneous abscesses in children. Their results closely correlate with those of Meislin and associates.  Brook and Finegold found aerobes (staphylococci and group A beta-hemolytic streptococci) to be the most common isolates from abscesses of the head, neck, extremities, and trunk, with anaerobes predominating in abscesses of the buttocks and perirectal sites. Mixed aerobic and anaerobic flora were found in the perirectal area, head, fingers, and nailbed area. This study found an unexpectedly high incidence of anaerobes in nonperineal abscesses. Anaerobes were found primarily either in areas adjacent to mucosal membranes, where these organisms tend to thrive (e.g., the mouth), or in areas that are easily contaminated (e.g., by sucking fingers, which causes nailbed and finger infections or bite injuries).
Parenteral drug users develop somewhat atypical abscesses. Webb and Thadepalli found anaerobes to be a major pathogen, regardless of anatomic location.  A more recent study of IV drug users found that skin abscesses at the site of injection contained predominantly staphylococcal and streptococcal species. Four of the 20 staphylococcal isolates were oxacillin resistant. Anaerobes and gram-negative bacilli accounted for 24% of the isolates.  Because IV drug use is associated with immunodeficiency syndromes, unusual isolates such as Candida albicans and acid-fast bacilli   have been obtained.
The polymicrobial nature of abscesses does not lend itself to a strict scientific interpretation of culture results, but if an unexpected or atypical organism is found in an abscess culture, the clinician should consider an underlying process not readily apparent from the history or physical examination. Most typical is finding tuberculosis or fungal isolates in immunocompromised patients (e.g., those with diabetes or acquired immunodeficiency syndrome [AIDS]). Finding E. coli suggests an enteric fistula or even self-inoculation of feces in psychiatric patients or in patients with Munchausen's syndrome. Recurrent abscesses without an obvious underlying cause could indicate clandestine drug use ("skin popping").
Parenteral drug users, insulin-dependent diabetics, hemodialysis patients, cancer patients, transplant recipients, and individuals with acute leukemias have an increased frequency of abscess formation compared with the general population. Local symptoms may not be the primary complaint, and the patient may present only with an exacerbation of the underlying disease process or an unexplained fever. These abscesses tend to have exotic or uncommon bacteriologic or fungal causes and typically respond poorly to therapy.     The diabetic patient with diabetes-induced ketoacidosis should be evaluated extensively for an infectious process; a rectal examination should be included with the physical examination to rule out a perirectal abscess. This also holds true for other patients with abnormal cell-mediated immunity. The increased frequency of abscess formation in these patients and in the parenteral drug user is multifactorial. There may be intrinsic immune deficiencies in all these patients; they have an increased incidence of Staphylococcus carriage, and they have frequent needle punctures which allow access by pathogenic bacteria. 
It is important to note that a substantial percentage of abscesses in parenteral drug users are sterile and are the result of the injection of necrotizing chemical irritants. Drug users frequently use veins of the neck and the femoral areas, producing abscesses and other infectious complications at these sites.  Any abscess near a vein of the antecubital fossa or dorsum of the hand should alert the physician to possible IV drug use; however, substance users may also inject directly into the skin ("skin popping"), causing cutaneous abscesses away from veins (Fig. 40-1) .
The presence of a foreign body may serve as a nidus for abscess formation. A history of a possible foreign body at the site of an abscess should be sought. Because IV drug users frequently break needles off in skin toughened by multiple injections, the clinician should maintain a high index of suspicion for retained needle fragments. If an abscess is recurrent or if the patient is a known or suspected IV drug user, radiographs or other techniques should be considered to search for foreign bodies. 
MANIFESTATIONS OF ABSCESS FORMATION
The diagnosis of cutaneous abscess formation is usually straightforward. The presence of a fluctuant mass in an area of induration, erythema, and tenderness is clinical evidence that an abscess exists. An abscess may appear initially as a definite tender soft tissue mass, but in some cases the presence of a distinct abscess may not be readily evident. If the abscess is quite deep, as is true of many perirectal, pilonidal, or breast abscesses, the clinician may be misled by the presence of only a firm, tender, indurated area without a definite mass. To avoid misdiagnosis of an early abscess, one may aspirate the suspicious infected area with a needle and syringe to confirm the presence of pus.  This approach also may help identify a mycotic aneurysm or an inflamed lymph node simulating an abscess. A specific entity that is commonly mistaken for a discrete abscess is the sublingual cellulitis of Ludwig's angina (see Chapter 69) . Cellulitis and abscess formation may lead to bacteremia and sepsis, especially in the immunocompromised patient, and the presenting complaints may draw attention from the primary focus of infection. 
Laboratory tests offer no specific guidelines for therapy of a cutaneous abscess and are not generally indicated. An exception would be a blood or urine glucose determination to assess diabetes in patients with appropriate clinical scenarios. An abscess may produce leukocytosis, depending on the severity and duration of the abscess process; however, the majority of patients with an uncomplicated cutaneous abscess will have a normal complete blood cell (CBC) count and will not experience fever, chills, or malaise. The presence or absence of leukocytosis has virtually no diagnostic or therapeutic implications.
Gram stain is not indicated in the care of uncomplicated simple abscesses. Patients who appear "toxic" or immunocompromised and those patients who require prophylactic antibiotics (see Prophylactic Antibiotics) may benefit from Gram stain and cultures. Gram stain results have been shown to correlate well with subsequent culture results, and in compromised hosts the test can be used to direct antibiotic choice.   Anaerobic infections should be suspected when multiple organisms are noted on Gram stain, when a foul odor is associated with the pus, when free air is noted on radiographs of the soft tissue, or when no growth is reported on cultures." 
In uncomplicated abscesses, routine culture is unnecessary because of the expected prompt response to surgical therapy and the polymicrobial nature of abscess formation. However, in complicated cases or in immunosuppressed patients, an abscess should be cultured. The information obtained may later be useful if there is poor response to the initial surgical drainage, secondary spread of the infection, or the occurrence of bacteremia.  If one takes a culture, it is best to aspirate the pus with a needle and syringe before incision and drainage. Material should be cultured for aerobic and anaerobic bacteria. The finding of a "sterile" culture in an abscess that has been cultured with a standard cotton swab after incision is frequently the result of improper anaerobic culture techniques. As a side note, there is a general misconception that foul-smelling pus is a result of E. coli. This foul odor is actually caused by the presence of anaerobes; the pus of E. coli is odorless.
INDICATIONS AND CONTRAINDICATIONS
Surgical incision and drainage is the definitive treatment of a soft tissue abscess.  Antibiotics alone are ineffective in the face of a localized collection of pus. The drainage of a suppurative focus results in a marked improvement in symptoms and rapid resolution of the infection in uncomplicated cases. Premature incision before localization of pus will not be curative and theoretically may be deleterious, because extension of the infectious process and bacteremia from manipulation can result. In some cases the application of heat to an area of inflammation may ease pain, speed resolution of the cellulitis, and facilitate the localization and accumulation of pus. It must be stressed that nonsurgical methods are not a substitute for surgical drainage and should not be continued for >24 to 36 hours before the patient is reevaluated. Diagnostic needle aspiration is recommended if one is unsure of pus localization.
ANCILLARY ANTIBIOTIC THERAPY
The use of antibiotics remains controversial for both prophylaxis and treatment of cutaneous abscesses. As an overview, there are no data that definitively demonstrate the need for antibiotic therapy in conjunction with incision and drainage of uncomplicated cutaneous abscesses in healthy, immunocompetent patients without valvular heart disease. The specific value of concomitant antibiotics in the immunocompromised patient, while intuitively attractive, is unclear. Patients with risk factors for endocarditis comprise a third group of patients. Because of the concern of inducing a bacteremia by manipulation of infected tissue, parenteral antibiotics are commonly given prior to the incision-and-drainage procedure in patients at risk from such bacteremia. Transient bacteremia has been documented (incidence range, 7 to 50%) following manipulation of noninfected tissue (brushing teeth, sigmoidoscopy, Foley catheter, rectal examination) and following simple incision and drainage of abscesses. In a report by Fine and colleagues, 6 of 10 patients with cutaneous abscesses were noted to have positive blood cultures immediately following incision and drainage, whereas all cultures were negative before the procedure.  Blick and associates evaluated the use of prophylactic antibiotics in abscesses managed in the operating room under general anesthesia. Three of 19 patients developed bacteremia after the procedure. A similar group treated with parenteral antibiotics before the procedure had only 1 patient with a positive blood culture. That culture yielded an organism resistant to the prophylactic antibiotic used. 
Prophylaxis for Endocarditis
The precise risk for endocarditis following incision and drainage of cutaneous abscess is unknown, and it is impossible to predict which patients will develop this infection or which particular procedure will be responsible. However, since bacteremia clearly occurs with manipulation of infected tissue, it is generally agreed that those patients at risk for cardiac complications related to transient bacteremia should be treated with appropriate antibiotics within the hour preceding the procedure. The transient bacteremia secondary to abscess drainage is probably of no concern in otherwise healthy, immunocompetent individuals without valvular heart disease.
No adequate controlled trials of antibiotic regimens appear in the literature, and data predicting the incidence of endocarditis in patients with preexisting cardiac disorders are lacking, thereby making the decision regarding antibiotic prophylaxis quite arbitrary. However, the Committee on Rheumatic Fever and Infective Endocarditis of the American Heart Association (AHA) has recommended that prophylactic antibiotics be given prior to incision and drainage of infected tissue in patients who have cardiac lesions that place them at high risk for developing endocarditis. Table 40-2 (Table Not Available) lists conditions that may warrant antibiotic coverage. Durack also recommends prophylactic antibiotics for a variety of procedures known to have a significant incidence of bacteremia, including incision and drainage of cutaneous abscesses.  Interestingly, the antibiotic regimen suggested by the AHA (Table 40-3) (Table Not Available) does not include antibiotics effective against many organisms commonly found in some cutaneous abscesses, specifically S. aureus, but is mainly directed against Streptococcus viridans and enterococcus. These latter organisms have a predilection for valvular infection. The AHA recommends the same prophylaxis for incision of soft tissue infection that is recommended for genitourinary procedures, but with additional consideration of therapy "directed against the most likely pathogen." 
Two clinical situations deserve special note. Because of the frequent incidence of endocarditis and previous valvular damage in the patient who uses IV drugs, prophylactic antibiotics may be indicated prior to the incision and drainage of abscesses in these patients. Clearly, any patient with a documented history of endocarditis must receive prophylactic antibiotics prior to the incision-and-drainage procedure. Because cutaneous abscesses may result from active endocarditis and prophylactic antibiotics may obscure subsequent attempts at identifying an etiologic organism, 2 or 3 blood cultures (aerobic and anaerobic) should be obtained from those at risk for endocarditis prior to antibiotic therapy. Patients with the diagnosis of mitral valve prolapse have traditionally been included for treatment with prophylactic antibiotics. The indication for this is unclear. The risk of an allergic reaction may outweigh the benefits of treatment in this group,  and clinical judgment is required. Kaye  suggests prophylaxis only for patients who have a holosystolic murmur secondary to mitral valve prolapse.
Prophylaxis for Bacteremia in Other Conditions
Immunocompromised patients have not been adequately studied, but this is a subgroup that intuitively may benefit from prophylactic antibiotics. In contrast to patients with endocarditis risks, immunocompromised patients are at risk for developing septicemia secondary to a brief bacteremia. Since IV drug users have a high incidence of human immunodeficiency virus (HIV)-related disease,    the treating physician must anticipate various degrees of immunodeficiency in these patients. Clinical judgment must determine the use of antibiotics in these situations.
No specific guidelines have been offered for the antibiotic regimen used prior to incision and drainage of infected cutaneous tissue in patients at risk for conditions other than endocarditis. Choice of antibiotics is guided by the organism anticipated to cause the bacteremia. Although the location of the abscess will give some clue to the organism involved, most abscesses contain multiple strains of bacteria. Not all bacteria are potent pathogens, so their mere presence does not predict their role in subsequent morbidity. Because Staphylococcus continues to be a significant organism in this setting, a broad-spectrum anti-staphylococcal drug is indicated.  Prophylaxis should consist of a single IV dose given a half hour prior to incision and drainage. A first-generation cephalosporin or penicillinase-resistant penicillin is a good initial choice. Vancomycin may also be considered. Others may prefer cefazolin (Ancef, Kefzol), 1 g, IV, given a half hour before surgery. This regimen covers staphylococcal and streptococcal species, many gram-negative organisms, and many anaerobes.
Although not widely used in the United States, parenteral antibiotics have been used to "sterilize" the abscess cavity following curettage in Great Britain. The concentration of clindamycin in the abscess cavity has been shown to be equivalent to the concentration of antibiotics found in the blood.  Some British articles report success with "primary closure under antibiotic coverage,"    although other British reports continue to recommend the traditional procedure.   One limitation to the abscess curettage technique is the need for general anesthesia, because the performance of curettage is extremely painful.
In contrast to prophylaxis prior to surgery, the routine use of oral antibiotics following incision and drainage of simple cutaneous abscesses in otherwise healthy patients with no immunocompromise appears to have virtually no value, and their empiric use cannot be scientifically supported. Llera and Levy  performed a randomized double-blind study to compare outcomes of patients treated with a first-generation cephalosporin following drainage of cutaneous abscesses in the ED. They found no significant difference in clinical outcome between the 2 groups and concluded that antibiotics are unnecessary in individuals with normal host defenses. This confirmed previous less well controlled studies.     It should be noted that high-risk patients were often excluded from these studies. The immunocompromised patient has not been adequately studied in this situation and is therefore often given antibiotics empirically, but this practice, while common, has not been supported by rigorous prospective studies.
Patients with cutaneous abscesses often have concomitant disease processes that may warrant the use of parenteral or oral antibiotics. Cellulitis or lymphangitis often accompany abscesses, and therapeutic antibiotics may have value under these circumstances, but again, this concept is not well addressed in the literature. Meislin noted that pathogen identification in cases of cellulitis without abscess can be difficult, and empiric antibiotics may be helpful.  IV drug users who present with an abscess and fever require parenteral antibiotic therapy after blood cultures have been drawn until subacute bacterial endocarditis can be ruled out.  Obviously, patients who are clinically septic require immediate IV antibiotics as well as aggressive surgical drainage of pus.
As a general guideline, therapeutic antibiotics should be given to all immunocompromised patients (e.g., patients with AIDS or diabetes, patients receiving chemotherapy or steroids, transplant recipients, and alcoholic patients) and to the immunocompetent patient with "significant" cellulitis, lymphangitis, or systemic symptoms, such as chills or fever. Although it has not been studied, it makes sense to also give antibiotics prophylactically, before surgery, to all patients who will obviously be given therapeutic antibiotics. As with prophylactic antibiotics, a first-generation cephalosporin or semisynthetic penicillin is a reasonable therapeutic choice unless the specific abscess site dictates alternative therapy. The ideal duration of therapeutic antibiotics is unknown. As a general guideline, immunocompromised patients should receive antibiotics for 5 to 7 days and immunocompetent patients, for 3 to 5 days after the procedure, depending on the severity of the condition and clinical response.
Facial abscesses should be handled carefully and checked frequently. Any abscess above the upper lip and below the brow may drain into the cavernous sinus, and thus manipulation may predispose to septic thrombophlebitis of this system. Treatment with antistaphylococcal antibiotics and warm soaks following incision and drainage has been recommended pending resolution of the process. Areas not in this zone of the face can be treated in a manner similar to that used for other cutaneous abscesses.
Definitive incision and drainage of soft tissue abscesses is performed in either the ED or the operating room (OR). The choice of the locale for the procedure depends on a number of important factors. Location of the abscess may dictate management in the OR. Large abscesses or abscesses located deep in the soft tissues require a procedure involving a great degree of patient cooperation, which may only be possible under general or regional anesthesia. Proximity to major neurovascular structures, such as in the axillae or antecubital fossa, may necessitate specific management. Infections of the hand (with the exception of distal finger infections) have traditionally been managed in the OR because of the many important structures involved and the propensity for limb-threatening complications.
Lack of adequate anesthesia is the most common limiting factor in ED incision and drainage. If the clinician believes the abscess cannot be fully incised and drained because of inadequate anesthesia, the patient should be taken to the OR for management under general anesthesia. In addition to limiting proper drainage, it is inhumane and unethical to subject a patient to extreme pain when alternatives are available.
When abscesses are drained in the ED, some centers prefer to use a special area of the ED to avoid contamination of general treatment rooms.
Equipment and Anesthesia
A standard suture tray provides adequate instruments if a scalpel and packing material are added. Although sterility is impossible during the procedure, one should avoid contamination of surrounding tissue. Some physicians prefer to use an obligatory skin scrub with an antiseptic solution, but the value of this step is dubious.
It is often quite difficult to obtain local anesthesia by direct infiltration because of the poor function of local anesthetic agents in the low pH of infected tissue. Furthermore, the distention of sensitive structures by a local injection is quite painful and hence poorly tolerated by most patients. Skin anesthesia is usually possible, but total anesthesia of the abscess cavity itself generally cannot be achieved. If a regional block can be performed (see Chapters 32 and 33) , this type of anesthesia is preferred. Alternatively, a field block may be used. It should be noted that infected tissue is very vascular, and local anesthetics are quickly absorbed. Strict adherence to maximum safe doses of the local anesthetic is required.
The skin over the dome of an abscess is often quite thin, making skin anesthesia difficult. If a 25-ga needle is carefully used, one can often inject the dome of the abscess subcutaneously. The anesthetic solution spreads over the dome through the SQ layers into the surrounding skin and provides excellent skin anesthesia. If the needle is in the proper plane (best accomplished by holding the syringe parallel, rather than perpendicular, to the skin), the surrounding skin blanches symmetrically during infiltration without having to reposition the needle (Fig. 40-2 A). In the extremely anxious or uncomfortable patient, the judicious use of preoperative sedation (see Chapter 35) with IV opioids and sedatives or nitrous oxide makes the procedure easier for both patient and physician. If adequate anesthesia cannot be obtained and pain limits the procedure, the patient should be treated under general anesthesia.
Some clinicians recommend the use of topical ethyl chloride or Fluori-Methane spray for the initial skin incision, but the pain relief offered by this agent is variable and fleeting. Ethyl chloride is also highly flammable. These vapocoolant sprays may be useful to provide momentary anesthesia for local anesthetic injection or for the initial skin incision if the injection or incision is made immediately after blanching of the skin. In general, however, this agent is a poor choice for a stand-alone anesthetic agent for all but the smallest of superficial abscesses (e.g., purulent folliculitis).
One should make all incisions conform with skin creases or natural folds to minimize visible scar formation (Fig. 40-3) (Figure Not Available) .
Extreme care should be taken in such areas as the groin, the posterior knee, the antecubital fossa, and the neck, so that vascular and neural structures are not damaged.
A No. 11 or 15 scalpel blade is used to nick the skin over the fluctuant area, and then a simple linear incision is carried the total length of the abscess cavity (see Fig. 40-2 B). This will afford more complete drainage and will facilitate subsequent breakup of loculations. A cruciate incision or an elliptical skin excision is to be avoided in the routine treatment of cutaneous abscess. The tips of the flaps of a cruciate incision may necrose, resulting in an unsightly scar. A timid "stab" incision may produce pus but is generally not adequate for proper drainage. It should be emphasized that the scalpel is used only to make the skin incision and is not used deep in the abscess cavity.
Exceptions to this rule regarding aggressive incision are abscesses in cosmetic areas, in areas under significant skin tension (e.g., extensor surfaces), or in areas with extensive scar tissue (e.g., sites of multiple prior drainage procedures). In these special circumstances, a stab incision or simple aspiration alone may be initially attempted, with the goal of limiting tissue injury and resultant scar formation. Use of this less aggressive approach requires that the patient be counseled that multiple decompressions (e.g., via needle aspiration) or delayed aggressive incision and drainage may be required. The abscess will need reassessment in 24 to 48 hours to determine the need for additional intervention.
Following a standard incision, the operator should probe the depth of an abscess to assess the extent of the abscess and ensure proper drainage by breaking open loculations (see Fig. 40-2 C). An ideal instrument for this procedure is a hemostat wrapped in gauze (or a cotton swab for small abscesses) that is placed into the abscess and swirled around to all sides of the cavity (see Fig. 40-2 D). Traditionally the operator's gloved finger has been suggested as an ideal way to assess the depth of the abscess cavity and to break up loculations, but this is a potentially dangerous practice that should be avoided unless it is certain that the abscess contains no sharp foreign body. Of particular concern is the abscess caused by skin popping or IV drug use. Such patients have a high incidence of HIV infection, and occasionally these abscesses harbor broken-off needle fragments (Fig. 40-4) . One is often surprised at the depth or extent of an abscess during probing. Sharp curettage of the abscess cavity is usually not required and may produce bacteremia.  Although tissue probing is usually the most painful aspect of the technique and total local anesthesia is difficult to obtain, this portion of the procedure should not be abbreviated. If the procedure is limited because of pain, the use of appropriate analgesia/anesthesia is mandated.
Following the breaking up of loculations, some physicians advocate copious irrigation of the abscess cavity with normal saline to ensure adequate removal of debris from the wound cavity. Although it may seem intuitively to be a helpful step, irrigation of the abscess cavity has not been experimentally demonstrated to significantly augment healing or affect outcome. Hyperemic tissue may bleed profusely, but bleeding usually stops in a few minutes if packing is used. Abscesses of the extremities can be drained during the use of a tourniquet to provide a bloodless field.
Packing and Dressing
After irrigation, a loose packing of gauze or other material is placed gently into the abscess cavity to prevent the wound margins from closing and to afford continued drainage of any exudative material that may otherwise be trapped. The packing material should make contact with the cavity wall so that upon removal, gentle debridement of necrotic tissue will spontaneously occur. A common error is to attempt to pack an abscess too tightly with excessive packing material. In essence, the pack merely keeps the incision open, and its main purpose is not to absorb all drainage--a dressing accomplishes this goal. Care must be exercised to ensure that the packing does not exert significant pressure against the exposed tissue and lead to further tissue necrosis. Some prefer to use plain gauze, some use gauze soaked in povidone-iodine, and some use gauze impregnated with iodine (iodoform). For large abscess cavities, gauze pads (without cotton backing) are ideal packing. If gauze pads are used, the number of pads placed in the wound should be counted and charted--ideally, the corner of each pad should exit from the wound. The clinician must ensure that all gauze pads will be removed when the packing is changed or discontinued. More commonly, thin (0.6 to 1.2 cm) packing strip gauze, either plain or iodoform, is used. The iodoform gauze may sting the patient for a few minutes after it is inserted. The value of antibiotic-impregnated gauze is uncertain.
An absorbent gauze dressing should be placed over the packed abscess, or, if an extremity is involved, a lightly wrapped circumferential dressing should be used. Generous amounts of dry gauze are used over the packing to soak up any drainage or blood. The affected part should be splinted if possible, and elevation should be routine. The dressing/splint should not be disturbed until the first follow-up visit. Drainage relieves most of the pain of an abscess, but postoperative analgesics may be required.
Following treatment, packing is often changed periodically. Most patients require a repeat visit to the physician for packing change, but if the original packing is to be removed and not replaced (paronychia, hair follicle abscess), selected patients may remove the packing and perform their own wound care totally at home.
Reevaluation of a drained abscess should occur in 1 to 3 days, depending on a number of parameters.    Most lesions are reevaluated 48 hours following the procedure, with the first packing change occurring at this time. Some wounds warrant closer monitoring. Diabetic patients or other patients with impaired healing capacity, mental impairment, or physical disabilities may require a home care nurse or admission for more frequent wound care/packing changes. Wounds that are at high risk for complications, such as those about the face or hands or those with significant cellulitis, require close follow-up, ideally by the same examiner. The patient should be encouraged to play an active role in wound care. During the first follow-up visit, the compliant and able patient should be taught to perform packing and/or dressing changes. If this is anatomically impossible, a friend or family member can be instructed in the technique.
The technique of packing change is usually one of personal preference. It should be emphasized that patients often fear a repeat visit and expect significant pain with subsequent wound care, especially if the initial incision drainage was difficult. Therefore, the specifics of packing change should be addressed prior to release home after the initial drainage procedure. Some clinicians suggest an oral opioid be taken 30 to 40 minutes before the next visit or use local anesthesia or parenteral analgesia if significant pain is anticipated. Removal of packing material is often painful, but if the packing is moistened with saline prior to removal, it may be less traumatic. Once the packing is removed, the wound is inspected for residual necrotic tissue. The cavity may be irrigated with saline prior to replacing the pack if there is significant exudate, but this is often not required because the packing absorbs most debris.
The frequency of packing or dressing changes is also clinically guided. Some wounds require multiple packing changes, while other wounds require only the initial packing. In all facial abscesses, the packing should be removed after only 24 hours, at which time warm soaks should be started. Wounds large enough to require packing should be repacked at least every 48 hours (occasionally daily for the first few visits) until healing continues in a deep to superficial direction. Large wounds that are allowed to close superficially will create an unsterile dead space that will potentiate the formation of recurrent abscesses. After the first few days (and in the motivated and compliant individual), an alternative to packing is to have the patient clean the base of the abscess 3 times a day with cotton swabs soaked in peroxide (Fig. 40-5) . This promotes drainage, produces gentle debridement, and keeps the incision open. Following cleaning, the abscess can be irrigated with tap water and a dry dressing applied.
In general, once healthy granulation tissue has developed throughout the wound and a well-established drainage tract is present, the packing may be discontinued. The patient should then be instructed to begin warm soaks of the wound.  Gentle hydrostatic debridement may be performed by the patient in the shower at home. With this procedure the patient holds the skin incision open and directs the shower or faucet spray into the abscess cavity. Wet-to-dry normal saline dressing changes should then follow until healing is completed. When all signs of infection (e.g., erythema, drainage, pain, and induration) have resolved and healthy granulation tissue is present, the patient may be discharged from medical care.
Complicated wounds that require prolonged care are best followed by a single physician and should not be routinely referred back to the ED. These patients should receive early referral to their primary care physician or specialist. Wounds in cosmetically important areas may require revision once healing is complete. Patients should be informed of this possibility early on in their care.
In selected cases in which extensive or prolonged drainage occurs or in patients who are unable to return for proper follow-up care, a catheter system of drainage may be preferred.   Following incision, a balloon-tipped or flared-tip catheter is placed into the abscess cavity, and pus is allowed to drain continuously through the catheter lumen. This technique has been most successful in pilonidal and Bartholin gland abscesses, but the technique is applicable to any abscess not on the face.
SPECIFIC ABSCESS THERAPY
The Staphylococcus bacterium is a ubiquitous pathogen that frequently colonizes the nose, skin, perineum, and gut. The umbilicus of neonates is also commonly colonized. It grows on the skin and thrives particularly well in hair follicles, causing boils (furuncles), wound infections, and occasionally carbuncles. The pathogenesis of staphylococcal disease is a complex host-bacteria interaction. S.aureus invades the skin by way of the hair follicles or an open wound and produces local tissue destruction followed by hyperemia of vessels. Subsequently, an exudative reaction occurs, during which polymorphonuclear cells invade. The process then extends along the path of least resistance. The abscess may "point" or form sinus tracts. The process can disseminate by invasion of vessels and thus can infect other organs. Most cases of staphylococcal osteomyelitis, meningitis, and endocarditis occur by this mechanism.  
Folliculitis represents a small abscess occurring at the root of a hair. Local measures, including warm compresses and antibacterial soaps and ointments, are the usual treatment, but systemic antibiotics may be required if multiple sites are involved or the patient is a chronic staphylococcal carrier. Furuncles, or boils, are acute circumscribed abscesses of the skin and SQ tissue that most commonly occur on the face, the neck, the buttocks, the thigh, the perineum, breast, or axilla. Carbuncles are aggregates of interconnected furuncles that frequently occur on the back of the neck (Fig. 40-6) . In this area the skin is thick, and extension therefore occurs laterally rather than toward the skin surface. Carbuncles may attain large size and can cause systemic symptoms and complications. They are found in increased frequency in diabetics, and all patients with a carbuncle should be evaluated for this underlying disease. Treatment should consist of surgical drainage and administration of systemic antibiotics. Large carbuncles may be impossible to drain adequately in the ED. Carbuncles usually consist of many loculated pockets of pus, and simple incision and drainage are often not curative. Occasionally, wide excision and skin grafting are required.
Most cases of recurrent staphylococcal skin infections are caused by autoinfection from existing skin lesions or nasal reservoirs. Prevention is directed at eliminating the organism. This is accomplished by application of bacitracin to the nares and by good hygiene, including frequent cleansing with antibacterial soap. If these measures are unsuccessful, then systemic oral antistaphylococcal treatment is instituted for 2 to 3 weeks. Detection and treatment of infection in family members may be necessary.  
S. aureus produces the ubiquitous suture abscess. A suture abscess is often misdiagnosed as a wound infection, but in fact, it is a local nidus of inflammation and/or infection caused and potentiated by suture material. Such an abscess usually appears after sutures have been present for at least 3 to 5 days, with single or multiple discrete areas of redness and tenderness noted at the site of suture penetration of the skin. Simply removing the suture (a drop of pus may be expressed) and providing warm compresses and topical antibiotic ointment is usually all that is required. Wide opening of the wound and systemic antibiotics are seldom required. When the suture is buried, a small incision should be followed by probing of the wound with a small hook or bent needle (see Chapter 39) to snare the suture for its removal.
Hidradenitis suppurativa (Greek hidros = sweat, aden = gland) is a chronic, relapsing, inflammatory disease process affecting the apocrine gland that primarily involves the axilla, the inguinal region, or both.  The condition results from occlusion of the apocrine ducts by keratinous debris, which leads to ductal dilation, inflammation, and rupture into the SQ area. Secondary bacterial infection ensues, leading to abscess formation and scarring. This chronic recurring process leads to draining fistulous tracts, which involve large areas and are not amenable to simple incision-and-drainage procedures. 
Genetic factors may play some role in hidradenitis suppurativa. Family history is often significant in these patients. Fitzsimmons has proposed a single dominant gene transmission.  Blacks appear to have an increased incidence compared with whites. Although certain groups appear to be predisposed to this condition, the precipitating factor for this process is unclear. Because apocrine glands become active during puberty, it is rare to find hidradenitis suppurativa in the pediatric population.  Women are affected more frequently than men, for uncertain reasons. Shaving and depilation have frequently been suggested as causes of this discrepancy; however, this theory was not supported in a study that compared the frequency of these behaviors in patients with hidradenitis suppurativa and a group of controls.  Obesity is associated with an increased incidence of the disease.  Excessive dermal folds provide dark, wet, and warm areas, which are ideal for the proliferation of the bacteria that are needed for this infectious process. Antiperspirants and deodorants may decrease wetness and bacterial overgrowth, but they have been known to produce inflammatory responses, which could exacerbate the disease process.
The bacteriology of acute abscess formation in hidradenitis suppurativa reflects organisms seen in other soft tissue abscesses. Staphylococcus is the most commonly isolated organism, with E. coli and beta-hemolytic Streptococcus being other important pathogens. In the perineal region, enteric flora are often found. Many of these abscesses have multiple isolates, and anaerobic bacteria are frequently found.
Hidradenitis suppurativa begins as a single inflammatory event involving an apocrine gland, which progresses to frank suppuration and at this stage is no different from a simple furuncle. The clinical entity is distinguishable only in its chronic scarring phase. By then the lesion exhibits multiple foci coupled with areas of induration and inflammation that are in various stages of healing. Progression of the process reveals coalesced areas of firm, raised violaceous dermis. The lesion is usually markedly tender. This disease classically involves the axilla and perineal or inguinal region, although multiple sites are often involved.
Initial outpatient management usually involves intervention in an acute suppurative lesion. Any fluctuant area requires drainage as described in the section on general abscess management. In cases of extensive cellulitis, a broad-spectrum, antistaphylococcal antibiotic should be used. Unfortunately, hidradenitis suppurativa is often not readily cured with localized incision and drainage. The chronic nature of the disease produces multiple areas of inflammation and SQ fistulous tracts that induce routine recurrences. The patient must be informed of this rather unfavorable prognosis and should be referred to a dermatologist or surgeon for long-term care.
Milder forms of the disease are initially treated with conservative measures. Many different approaches have been tried, with numerous case reports and case series noted in the literature. Unfortunately, few controlled studies have been performed. Patients are often counseled to lose weight, refrain from shaving, stop using deodorants, and improve personal hygiene. The benefits of these efforts are unknown. Oral antistaphylococcal antibiotics are most commonly used, with varying results.  There have been reports of success with topical clindamycin,  isotretinoin,   and laser therapy,  but these treatments have not been studied in a controlled setting and require further investigation. Dermal infection results from breakdown of the normal host defense mechanism, which occurs with irritation, traumatic injury, or inflammation, coupled with the availability of concentrated opportunistic bacteria. Therefore, the physician must institute therapies that will decrease bacterial availability without causing further injury to the affected dermis.
Advanced stages of the disease are routinely managed with wide or local excision and primary or delayed closure.    Despite this radical approach, recurrences do occur.  Patients must be counseled about the likelihood of recurrence before the procedure.
Postpartum mastitis occurs in 1 to 3% of nursing mothers within the first 2 to 6 weeks after delivery. The infection is usually precipitated by milk stasis following weaning or missed feedings. The cause is usually bacterial invasion through a cracked or abraded nipple by S. aureus or streptococci originating from the nursing child. Manifestations are redness, heat, pain, fever, and chills. Treatment consists of antistaphylococcal antibiotics, continued breast emptying with a breast pump, and application of heat. It is important to encourage continued breast emptying to promote drainage. Nursing can be continued with the noninfected breast, although passage of the antibiotics through the breast milk may result in some infant diarrhea. Cellulitis may progress to frank abscess formation. These patients may be quite ill and may appear toxic. Abscess formation complicating postpartum mastitis usually necessitates OR management, because the area is extremely tender, and adequate local anesthesia is difficult to obtain. Strict adherence to nipple hygiene to avoid cracks or inflammation is helpful in prophylaxis.
Surprisingly, most breast abscesses occur in women who are not in the puerperium, and have been termed nonpuerperal breast abscesses.  Scholefield and coworkers reviewed 72 breast abscesses over a 10-year period and noted that only 8.5% of patients were in the puerperium.  These lesions have been classified anatomically.
Peripherally located abscesses are most commonly caused by Staphylococcus and respond well to traditional conservative incision and drainage.  Superficial abscesses in the SQ tissue may be drained under local anesthesia by means of an incision that radiates from the nipple (Fig. 40-7 (Figure Not Available) A).
Periareolar abscesses exhibit a more troublesome profile. The microflora often include multiple organisms, and anaerobic bacteria are important isolated pathogens.     These infections may be the result of occluded and inflamed mammary ducts. Chronic disease may lead to ductal ectasia that provides a nidus for infection. The deeper and more extensive intramammary abscess appears as a generally swollen, tender breast (Fig. 40-7 (Figure Not Available) B). Fluctuance is not always obvious, since the abscess is located in the mammary tissue itself. Maier and colleagues reported that more than half of their series of 96 patients had nipple inversion due to chronic scarring.  These intramammary infections are complex and require incision and drainage under general anesthesia. Dixon has reported successful treatment with repeated aspiration in both lactating  and nonlactating patients.  This approach is probably best left to surgeons able to see such patients on a regular scheduled basis to track the progress of abscess resolution.
A retromammary abscess lies in the undersurface of the breast between the breast and the chest wall (Fig. 40-7 (Figure Not Available) C). Fluctuance may be difficult to appreciate because of the depth of the infection. Drainage under general anesthesia is required.
Recurrent abscesses are a common, troublesome complication, occurring in up to 38% of primary periareolar abscesses treated with standard incision, drainage, and antibiotics.  These cases require total excision of the involved area and necessitate the care of a general surgeon and further intraoperative management. It may be difficult to diagnose a breast abscess in the early stages, when cellulitis predominates. In equivocal cases antibiotics may be curative, but when pus is present, incision and drainage must be performed.
Bartholin Gland Abscess
The Bartholin glands (vestibular glands) are secretory organs located at the 5 and 7 o'clock positions on each side of the vestibule of the vagina. Asymptomatic cysts frequently occur from duct blockage and retention of secretions. Chronic low-grade inflammation from gonococcal infections has been implicated as an etiologic factor in cyst formation, but occasionally frank abscess formation results. Such patients present with swollen and tender labia and a fluctuant, grape-sized mass that may be palpated between the thumb and the index finger. Neisseria gonorrhoeae organisms are infrequently cultured from the abscess cavity, and various anaerobes, especially Bacteroides species and other colonic bacteria, are usually found. It is reasonable to take cervical and anal cultures for gonorrhea from women with Bartholin gland abscesses because of the association of these infections with venereal disease, but one need not routinely treat patients for gonorrhea.
Word  has described an effective treatment of Bartholin gland abscess with a single-barreled, sealed-stopper, balloon-tipped catheter that may obviate the need for marsupialization (Fig. 40-8 (Figure Not Available) A and B). In his original description, Word reports only 2 recurrences in 72 lesions, both of which were successfully treated with a second catheter; no patient required marsupialization. The procedure involves fistulization of the duct cavity by a catheter, which acts as a foreign body. While not a standard incision-and-drainage procedure, the technique permits continued drainage of the Bartholin gland.
Following a small incision into the mucosa, the scalpel or a hemostat is used to puncture the abscess cavity proper (Fig. 40-9) . It is helpful to stabilize the abscess with the thumb and forefinger to ensure entrance into the abscess. Care is required to make a stab incision only large enough
Figure 40-8 (Figure Not Available) Use of the Word catheter for outpatient drainage of a Bartholin gland abscess. This is a fistulization procedure rather than a standard incision and drainage. A stab incision is made on the mucosal surface (A). A catheter is inserted into the cyst cavity (B) and filled with 3 to 4 mL of water (C). D, Inflatable bulb-tipped catheter. Left, Uninflated. Right, Inflated with 4 mL water. ( A through C from Word B: Office treatment of cyst and abscess of Bartholin gland. JAMA 190:777, 1964. D from Word B: Office treatment of cyst and abscess of Bartholin's gland duct. South Med J 61:514, 1968. Reproduced with permission.)
to accommodate the catheter and small enough to prohibit the inflated balloon from being extruded. Once the abscess has been entered (signaled by the free flow of pus), the deflated balloon is placed in the abscess cavity. Using a 25-ga needle to minimize the hole in the stopper, the balloon is then filled with 2 to 4 mL of water (not air). Persistent pain indicates that too much fluid has been used. The device is left in place for 6 to 8 weeks to allow for fistula formation, so follow-up is required. If the catheter falls out prematurely, it should be quickly replaced to fulfill the 6 to 8 weeks needed for fistulization. This is an interesting technique that even allows for sexual intercourse with the catheter in place.
The initial treatment of a Bartholin gland abscess may also include simple incision and drainage. The abscess is packed for 24 to 48 hours, and sitz baths are started after the first revisit. Broad-spectrum antibiotics are helpful if there is significant cellulitis or actual abscess formation has not yet occurred, but these agents are not required following routine incision and drainage.
It is preferable to make the drainage incision on the mucosal surface rather than on the skin surface. The incision is made over the medial surface of the introitus on a line parallel to the posterior margin of the hymenal ring. The abscess cavity is slightly deeper than most cutaneous abscesses, and one must be certain to enter the actual abscess cavity to achieve complete drainage. This is most easily accomplished if one inserts a hemostat through the mucosal incision and spreads the tips of the instrument in the deeper soft tissue. If the abscess recurs, more definitive therapy in the form of marsupialization or complete excision of the gland may be required, but these procedures are not performed initially. Because recurrence is common with simple incision and drainage, some authorities suggest definitive surgery routinely following the first infection, whereas others prefer to wait until a recurrence is documented.
Pilonidal sinuses are common malformations that occur in the sacrococcygeal area. The etiology of the sinus formation is unclear, but the malformation may occur during embryogenesis. Pilonidal cyst formation is thought to be secondary to blockage of a pilonidal sinus. The result of pilonidal sinus obstruction is repeated soft tissue infection, followed by drainage and partial resolution with eventual reaccumulation. The blockage is most commonly the result of hairs in the region, and the lesion may in part be a foreign body (hair) granuloma. Although pilonidal sinuses are present from birth, they usually are not manifested clinically until adolescence or the early adult years, and pilonidal abscess formation most commonly affects young (often white) adults. The sinuses and cysts are lined with stratified squamous epithelium and may contain wads of hair and debris when excised. When cultured, pilonidal abscesses generally yield mixed fecal flora with a preponderance of anaerobes. 
The patient with a pilonidal abscess will seek care for back pain and local tenderness. On physical examination the area is indurated, but frank abscess formation may not be appreciated. One will usually see barely perceptible dimples or tiny openings at the rostral end of the gluteal crease (Fig. 40-10) (Figure Not Available) . A hair or a slight discharge may be noticed at the opening. One may find a more caudal cyst or abscess, possibly with a palpable sinus tract connecting the two. The sinus and cyst may be chronically draining, or they may become infected as the size increases and blockage occurs. 
Treatment of the acutely infected cyst is the same as previously discussed for any fluctuant abscess; all hair and pus should be removed, and the lesion should be packed. Antibiotic therapy is not usually required. The abscess cavity may become quite large, necessitating a rather lengthy incision to ensure complete drainage. It may take many weeks for the initial incision to heal. The area may be repacked at 2- to 4-day intervals as an outpatient procedure, although some prefer to discontinue packing after the first week.
Figure 40-10 (Figure Not Available) Pilonidal sinus. A, Sinuses occur in the midline some 5 cm above the anus in the natal cleft. B, Longitudinal section showing sinuses and pits. (From Hill GJ II: Outpatient Surgery. 3rd ed. Philadelphia, WB Saunders, 1988. Reproduced with permission.)
Figure 40-11 (Figure Not Available) A method of prolonged drainage of a pilonidal abscess with a flared-end Pezzer catheter. Following a stab incision, a stretched catheter (probe inside lumen) is inserted into the abscess cavity (A). When the probe is removed, the head of the catheter expands and remains in the abscess cavity (B). Drainage is continuous through the lumen of the catheter. (From Phillip RS: A simplified method for the incision and drainage of abscesses. Am J Surg 135:721, 1978. Reproduced with permission.)
Because simple incision and drainage are often not curative, secondary removal of both the cyst and the sinus should be planned after the inflammatory process has resolved. The elective surgical procedure should be complete and should involve all of the possible arborizations of the sinus.
Recurrence is occasionally prevented by simple incision and drainage, especially if the incision is wide, and adequate drainage is obtained. More commonly, recurrence can be expected unless excision of the sinus tract is performed. Small abscesses may be incised and drained as an outpatient procedure performed under local anesthesia, but the disease process is often extensive, and general anesthesia may be required to complete drainage. One is often surprised by the extent of the cyst cavity and the volume of pus that is encountered when the area is probed during initial incision; because of the degree of these abscesses, only localized infection lends itself to outpatient therapy. A method of catheter drainage for pilonidal abscesses has been described   in which a flared-end Pezzer catheter is used for extended periods in the abscess cavity. The catheter allows the patient more freedom from local care and provides continual drainage (Fig. 40-11) (Figure Not Available) .
Perirectal infections can range from minor irritations to fatal illnesses. Successful management depends on early recognition of the disease process and adequate surgical therapy. Because of the morbidity and mortality associated with inadequate treatment of these conditions, patients with all but the most localized abscesses should be promptly admitted to the hospital for evaluation and treatment under general or spinal anesthesia.
It is important to understand the anatomy of the anal canal and the rectum in order to appreciate the pathophysiology of these abscesses and their treatment (Fig. 40-12) (Figure Not Available) . The mucosa of the anal canal is loosely attached to the muscle wall. At the dentate line, where columnar epithelium gives way to squamous epithelium, there are vertical folds of tissue, called the rectal columns of Morgagni, which are connected at their lower ends by small semilunar folds called anal valves. Under these valves are invaginations termed anal crypts. Within these crypts are collections of ducts from anal glands. These glands are believed to be responsible for the genesis of most, if not all, perirectal abscesses. These glands often pass through the internal sphincter but do not penetrate the external sphincter.
The muscular anatomy divides the perirectal area into compartments that may house an abscess, depending on the direction of spread of the foci of the infection (Fig. 40-13) (Figure Not Available) .   The circular fibers of the intestinal coat thicken at the rectum-anus junction to become the internal anal sphincter. The muscle fibers of the levator ani fuse with those of the outer longitudinal fibers of the intestinal coat as it passes through the pelvic floor. These conjoined fibers then are connected by fibrous tissue to the external sphincter system, which consists of three circular muscle groups.
As described previously, the anal glands are mucus-secreting structures that terminate in the area between the internal and external sphincters. It is believed that most perirectal infections begin in the intersphincteric space secondary to blockage and subsequent infection of the anal glands. Normal host defense mechanisms then break down, followed by invasion and overgrowth by bowel flora. 
If the infection spreads across the external sphincter laterally, an ischiorectal abscess is formed. If the infection dissects rostrally, it may continue between the internal and external sphincters, causing a high intramuscular abscess. The infection may also dissect through the external sphincter over the levator ani to form a pelvirectal abscess. 
When infection of an anal crypt extends by way of the perianal lymphatics and continues between the mucous membrane and the anal muscles, a perianal abscess forms at the anal orifice. The perianal abscess is the most common variety of perirectal infection. The abscess lies immediately beneath the skin in the perianal region at the lowermost part of the anal canal. It is separated from the ischiorectal space by a fascial septum that extends from the external sphincter and is continuous with the SQ tissue of the buttocks. The infection may be small and localized or very large, with a wall of necrotic tissue and a surrounding zone of cellulitis.  Perianal abscesses may be associated with a fistula in ano. The fistula in ano is an inflammatory tract with an external opening in the skin of the perianal area and an internal opening in the mucosa of the anal canal. The fistula in ano is usually formed after partial resolution of a perianal abscess, and its presence is suggested by recurrence of these abscesses with intermittent drainage. The external opening of the fissure is usually a red elevated piece of granulation tissue that may have purulent or serosanguineous drainage on compression. Many times the tract may be palpated as a cord. Patients with anal fistulas should be referred for definitive surgical excision. 
Ischiorectal abscesses are fairly common. They are bounded superiorly by the levator ani, inferiorly by the fascia over the perianal space, medially by the anal sphincter muscles, and laterally by the obturator internus muscle. These abscesses may commonly be bilateral, and if so, the 2 cavities communicate by way of a deep postanal space to form a "horseshoe" abscess. 
Intersphincteric abscesses are less common. They are bounded by the internal and external sphincters and may extend rostrally into the rectum, thereby separating the circular and longitudinal muscle layers.
The pelvirectal, or supralevator, abscess lies above the levator ani muscle in proximity to the rectal wall and remains extraperitoneal. The etiology of this abscess is controversial. Kovalcik and colleagues  suggest that supralevator abscesses are primarily an extension of an intra-abdominal process, such as diverticulitis or pelvic inflammatory disease. Read and Abcarian  evaluated 404 patients with perirectal abscesses in a prospective study and found that of the 36 supralevator abscesses, none was caused by an intra-abdominal or pelvic pathologic condition. They determined that supralevator abscesses were most commonly associated with ischiorectal abscesses and suggested that these conditions may be an extension of ischiorectal abscesses through the floor of the levator ani. Nonetheless, they found rare isolated pelvirectal abscesses without intra-abdominal, pelvic, ischiorectal, or perianal infection.
Causes of perirectal abscesses other than the so-called cryptoglandular process have been documented but are fairly rare. It is believed that hemorrhoids, anorectal surgery, episiotomies, or local trauma may cause abscess formation by altering local anatomy and thus destroying natural tissue barriers to infections.   
Anorectal abscesses occur most commonly in healthy adults and are more frequent in males (>2:1 ratio).   These abscesses commonly appear during the fourth decade of life. Possible predisposing medical conditions are diabetes mellitus, inflammatory bowel disease, and other immunocompromised states. Many patients (30%) have a history of previous perirectal abscess, and 75% of anorectal abscesses occur in the same location as the prior abscesses.  Of perirectal abscesses, usually >45% are perianal, 20% are ischiorectal, 12% are intersphincteric, and 7% are pelvirectal. 
Physical and Laboratory Findings
The diagnosis of a perianal abscess is generally not difficult. The throbbing pain in the perianal region is acute and is aggravated by sitting, coughing, sneezing, and straining. There is swelling, induration, and tenderness, and a small area of cellulitis is present in proximity to the anus. Rectal examination of the patient with a perianal abscess reveals that most of the tenderness and induration is below the level of the anal ring.
Patients with ischiorectal abscesses present with fever, chills, and malaise, but at first there is less pain than with the perianal abscess. Initially on physical examination, one will see an asymmetry of the perianal tissue, and later erythema and induration become apparent. Digital examination reveals a large, tense, tender swelling along the anal canal that extends above the anorectal ring. If both ischiorectal spaces are involved, the findings are bilateral.
Patients with intersphincteric abscesses usually present with dull, aching pain in the rectum rather than in the perianal region. No external aberrations of the perianal tissues are noted, but tenderness may be present. On digital examination one frequently palpates a soft, tender, sausage-shaped mass above the anorectal ring; if the mass has already ruptured, the patient may give a history of passage of purulent material during defecation.   
Diagnosis of pelvirectal abscesses may be very difficult. Usually fever, chills, and malaise are present, but because the abscess is so deep seated, few or no signs or symptoms are present in the perianal region. Rectal or vaginal examination may reveal a tender swelling that is adherent to the rectal mucosa above the anorectal ring.
Laboratory findings usually do not aid in the diagnosis. Kovalcik and coworkers  found that <50% of their patients had a white blood cell count >10.0 ¥ 109 /L. Cultures of perirectal abscesses usually show mixed infections involving anaerobic bacteria, most commonly Bacteroides fragilis and gram-negative enteric bacilli.
Successful management of perirectal abscesses depends on adequate surgical drainage. Complications from these infections may necessitate multiple surgical procedures, prolong hospital stay, and result in sepsis and death. Bevans and associates  retrospectively studied the charts of 184 patients who were surgically treated over a 10-year period. These patients were evaluated primarily to identify the factors that contributed to morbidity and mortality. Initial drainage was performed under local anesthesia in 38% of the patients and under spinal or general anesthesia in 62%. The authors identified 3 key factors in excessive morbidity and mortality: (1) a delay in diagnosis and treatment, (2) inadequate initial examination or treatment, and (3) associated systemic disease. It was their belief that the only way to examine effectively and drain adequately all but the most superficial perirectal abscesses was under spinal or general anesthesia. This assessment was supported by evidence of an increased incidence of recurrence and of sepsis and death in patients treated with local anesthesia. Drainage under local anesthesia generally does not allow drainage of all hidden loculations. In addition, local anesthesia is not adequate for treatment of associated pathologic conditions.
Small, well-defined perianal abscesses are the only perirectal infections that lend themselves to outpatient therapy. The result of incision and drainage is almost immediate relief of pain and rapid resolution of infection. Indications for inpatient drainage are failure to obtain adequate anesthesia, systemic toxicity, extension of the abscess beyond a localized area, or recurrence of a perianal abscess. Recurrence may be caused by the presence of a fistula in ano.
A perianal abscess is drained through a single linear incision over the most fluctuant portion of the abscess in a manner previously described for other cutaneous abscesses. It is extremely painful to probe a perianal abscess and to break up loculations, and liberal analgesia is advised. The patient may begin sitz baths at home 24 hours following surgery. Packing is replaced at 48-hour intervals until the infection has cleared and granulation tissue has appeared. This usually occurs within 4 to 6 days. Antibiotics are generally not required. All other perirectal abscesses require hospitalization for definitive therapy.
Use of Pezzer catheters in anorectal abscesses has been described as an alternative to traditional incision and packing. Kyle and Isbister reported a series of 91 patients treated in this manner. They found equivalent rates of subsequent fistula surgery, less need for general anesthesia, and a shorter postoperative hospital stay when compared with patients treated with traditional incision and packing.  Beck and colleagues reported successful use of catheter drainage in 55 patients with ischiorectal abscess.  Due to the complexity of ischiorectal abscesses, this technique is probably best left to the surgeon providing ongoing care.
Perirectal abscesses are currently recognized as a fairly common cause of fever in the granulocytopenic patient. These abscesses have a different bacteriologic profile: Pseudomonas aeruginosa organisms are isolated most frequently. These patients present later because pain develops later in the course, and fever may be the first manifestation. Therefore, any patients who are granulocytopenic with vague anorectal complaints, especially those with fever, should be examined carefully for perirectal abscesses. Any abscess that is found should be drained immediately under appropriate anesthesia, and extensive IV antibiotic coverage should be initiated.
Infected Sebaceous Cyst
A common entity that appears as a cutaneous abscess is the infected sebaceous cyst. Sebaceous cysts may occur throughout the body and result from obstruction of sebaceous gland ducts. The cyst becomes filled with a thick, cheesy sebaceous material, and the contents frequently become infected. Sebaceous cysts may be quite large and may persist for many years before they become infected. When infected, they clinically appear as tender, fluctuant SQ masses, often with overlying erythema.
The initial treatment of an infected sebaceous cyst is simple incision and drainage. The thick sebaceous material must be expressed, since it is too thick to drain spontaneously (Fig. 40-14 A). An important difference exists between infected sebaceous cysts and other abscesses. A sebaceous cyst has a definite pearly white capsule that must be excised to prevent recurrence (Fig. 40-14 B and C). Traditionally, in the presence of significant inflammation, it is preferable to drain the infection initially and remove the shiny capsule on the first follow-up visit or a later visit, when it may be more easily identified. Alternatively, the entire cyst can be removed at the time of initial incision. At the time of capsule removal, the edges are grasped with clamps or hemostats, and the entire capsule is removed by sharp dissection with a scalpel or scissors. Following excision of the capsule, the area is treated in the same manner as a healing abscess cavity. Simple drainage without excision of the capsule often leads to recurrence.
Kitamura and associates reported a randomized study of 71 patients treated with either traditional incision and drainage or primary resection of the cyst, followed by irrigation and wound closure. In this study, the patients treated with primary resection had faster healing, fewer days of pain, and less scarring. 
A paronychia is an infection localized to the area around the nail root (Fig. 40-15) (Figure Not Available) . Paronychias are common infections probably caused by frequent trauma to the delicate skin around the fingernail and the cuticle. When a minor infection begins, the nail itself may act like a foreign body. Usually the infectious process is limited to the area above the nail base and underneath the eponychium (cuticle), but occasionally it may spread to include tissue under the nail as well, forming a subungual abscess. Lymphadenitis and lymphadenopathy are usually not seen. Generally, a paronychia is a mixed bacterial infection. Staphylococcus is commonly cultured from these lesions; however, anaerobes and numerous gram-negative organisms may be isolated.  Paronychias in children are often caused by anaerobes, and it is believed that this is the result of finger sucking and nail biting. Occasionally, a group A beta-hemolytic infection will develop in a paronychia if a child with a streptococcal pharyngitis puts his or her fingers in the mouth. 
A paronychia appears as a swelling and tenderness of the soft tissue along the base or the side of a fingernail (Fig. 40-16) . Pain, often around a hangnail, usually prompts a visit to the ED. The infection begins as a cellulitis and may form a frank abscess. If the nailbed is mobile, the infectious process has extended under the nail, and a more extensive drainage procedure should be performed. If soft tissue swelling is present without fluctuance, remission may be obtained from frequent hot soaks (6 to 8 times a day) and a short course of oral antibiotics (3 to 4 days).  Incision will be of no value at this early cellulitic phase. If a significant cellulitis is present, a broad-spectrum antistaphylococcal antibiotic (cephalosporin or semisynthetic penicillin) may be tried. However, plain penicillin or erythromycin is often sufficient for limited inflammation. The digit should be splinted and elevated.   One should never rely solely on antibiotic therapy once frank pus has formed.
When a definite abscess has formed, drainage is usually quickly curative. A number of invasive operative approaches have been suggested, but actual skin incision or removal of the nail is rarely required, and neither procedure should be the initial form of treatment. One can invariably obtain adequate drainage by simply lifting the skin edge off the nail to allow the pus to drain. This is usually curative, because a paronychia is not a cutaneous abscess per se, but rather a collection of pus in the potential space between the cuticle and proximal fingernail. Drainage may be accomplished without anesthesia in selected patients but frequently requires a digital nerve block. After softening the eponychium by soaking, a No. 11 blade, scissors, or an 18-ga needle is advanced parallel to the nail and under the eponychium at the site of maximal swelling (Fig. 40-17) .   Pus rapidly escapes, with immediate relief of pain. A tourniquet placed at the base of the finger may limit bleeding and aid the physician in determining the exact extent of the infection during the drainage procedure.
If more than a tiny pocket of pus is present, one should fan the knife tip or needle or spread the scissors under the eponychium, keeping the instrument parallel to the plane of the fingernail. When a large amount of pus is drained, a small piece of packing gauze is slipped under the eponychium for 24 hours to provide continual drainage. Cultures are generally not indicated. Antibiotics are frequently prescribed, although they are not essential if drainage is complete or if the surrounding area of cellulitis is minimal. An alternative to systemic antibiotics is to keep the operative site bathed in antibiotic ointment. After anesthesia has worn off, the patient may be started on frequent soaks in warm tap water at home. In most cases the patient may easily remove the packing. At 24 to 36 hours, the finger is soaked in hot water and the gauze pulled out; a repeat visit to a physician is not required if healing is progressing. Once the packing is removed, the area is covered with a dry, absorbent dressing. An antibiotic ointment may be applied to the site for a few days. The benefit of antibiotic ointments in reducing infection is unproved, but instructing the patient concerning the use of the ointment may prompt soaking. In addition, the ointment helps to keep the bandage from sticking.
If the infection has produced purulence beneath the nail (subungual abscess), a portion of the nail must be removed or the nail trephined to ensure complete drainage. As an alternative to nail removal, a hole may be placed in the proximal nail with a hot paper clip. A large opening or multiple holes are required to ensure continued drainage. Most commonly the proximal portion of the nail is involved. This may be treated by bluntly elevating the eponychium to expose the proximal edge of the nail. The proximal one third of the nail is then elevated from the nailbed and resected with a scissors. The distal two thirds of the nail is left in place to act as a physiologic dressing and to decrease postoperative pain (Fig. 40-18) . If purulence is found below the lateral edge of the nail, the affected part may be gently elevated and excised longitudinally.  Care must be exercised during this procedure to avoid damage to the nail matrix. A wick of gauze should be placed beneath the eponychium for 48 hours to ensure continued drainage.
Most paronychia resolve in a few days, and 1 to 2 postoperative visits should be scheduled to evaluate healing and reinforce home care. For compliant patients with a small paronychia, home care alone may suffice after the initial drainage. A well-known complication of even a properly drained paronychia is osteomyelitis of the distal phalanx. Clinical infection lasting longer than a few weeks should prompt evaluation for this complication.
Patients occasionally present to the ED complaining of a chronic, indolent infection of the paronychium. These seldom respond to ED intervention. Frank purulence is seldom present, and conservative treatments are often unsatisfactory. Many etiologies have been described for this frustrating condition, including fungal, bacterial, viral, and psoriatic conditions. Treatment modalities are varied, and controlled studies evaluating the various techniques are lacking. Meticulous hand care, oral and topical antimicrobial medications, and occasionally aggressive surgical intervention have been suggested.   These patients should be referred to a dermatologist or hand surgeon because of the prolonged treatment required.
Herpetic whitlow is an infection of the distal phalanx caused by the herpes simplex virus. Digital inoculation occurs through a discontinuity of the skin.  Health care providers and patients with other herpes infections are most commonly infected.     The entity is recognized by the presence of herpetic vesicles, a burning or pruritic sensation, absence of frank pus, slow response to treatment, and a tendency to recur. In questionable cases, viral cultures can be obtained. Herpetic lesions are generally quite painful but are self-limited and resolve in 2 to 3 weeks. Surgical intervention is contraindicated, as this may potentiate a secondary bacterial infection and delay healing.     Treatment is symptomatic, consisting of splinting, elevation, and analgesia as needed. Antibiotics effective against herpes infections (acyclovir, famciclovir, and others) probably shorten the course of the disease if given early. Consideration must be given to preventing spread of the infection to other individuals. Although an occlusive dressing may lessen the chance for viral transmission, any health care provider with this entity should refrain from patient contact until all lesions have crusted over and viral shedding has stopped.   
A felon is an infection of the pulp of the distal finger (Fig. 40-19) . The usual cause is trauma with secondary invasion by bacteria. A felon may develop in the presence of a foreign body, such as a thorn or a splinter, but often a precipitating trauma cannot be identified. An important anatomic characteristic of this area is that there are many fibrous septa extending from the volar skin of the fat pad to the periosteum of the phalanx; these subdivide and compartmentalize the pulp area. When an infection occurs in the pulp, these same structures make it a closed space infection. The septa limit swelling, delay pointing of the abscess, and inhibit drainage after incomplete surgical decompression. Pressure may increase in the closed space, initiating an ischemic process that compounds the infection. The infection can progress readily to osteomyelitis of the distal phalanx. Although the septa may facilitate an infection in the pulp, they provide a barrier that protects the joint space and the tendon sheath by limiting the proximal spread of infection.
The offending organisms are usually Staphylococcus or Streptococcus, although mixed infections and gram-negative infection may occur. A felon is one of the few soft tissue infections in which a culture may be helpful, since osteomyelitis and prolonged infection may occur. An initial culture may aid in the subsequent choice of antibiotics for complicated infections.
The patient developing a felon will describe gradual onset of pain and tenderness of the fingertip. In a few days the pain may be constant and throbbing and gradually becomes severe. In the initial stages, physical examination may be quite unimpressive, because the fibrous septa limit swelling in the closed pulp space. As the infection progresses, swelling and redness may become obvious. Occasionally one may elicit point tenderness, but frequently the entire pulp space is extremely tender. The patient characteristically arrives with the hand elevated over the head because pain is so intense in the dependent position. Cessation of pain indicates extensive necrosis and nerve degeneration.
Proper treatment of a well-developed felon consists of early and complete incision and drainage.  Antibiotics alone are not curative once suppuration has occurred. Delaying surgery may result in permanent disability and deformity. Most surgeons routinely administer broad-spectrum antibiotics to patients for 5 to 7 days following surgical incision.
The surgery can usually be performed as an outpatient procedure using a digital nerve block. A long-acting solution (bupivacaine) will prolong anesthesia. A tourniquet (1.25 cm Penrose drain) should be used to allow digital incision in a bloodless field.
Surgical drainage must be carefully performed to avoid injury to digital nerves, vessels, and flexor tendon mechanisms. Most commonly, a felon can be successfully managed with a limited procedure, but many surgical options have been advocated, none of which has been proven superior for all circumstances.  The preferred initial treatment is a simple longitudinal incision made over the area of greatest fluctuance,  which may occur laterally or along the volar surface (Fig. 40-20) . A potential drawback to an incision in the middle of the fat pad is the production of a scar in a very sensitive and commonly traumatized area. The incision must not extend to the distal interphalangeal crease because of the danger of injuring the flexor tendon mechanism. The SQ tissue is bluntly dissected using a hemostat to provide adequate drainage. A gauze pack may be placed in the wound for 24 to 48 hours to ensure continued drainage.
Recurrent or more severe infections may require a more aggressive approach. The following traditional incisions have a greater propensity for complications such as sloughing of tissue and postoperative fat pad anesthesia or instability,  although they may provide for more complete drainage.
The hockey-stick incision is a well-accepted drainage procedure (Fig. 40-21) (Figure Not Available) . This incision is advantageous if the infection points to 1 side of the finger. The incision begins in the midline of the tip of the fat pad, just under the distal edge of the fingernail. It is extended to the lateral tip of the finger and proximally along the side of the distal phalanx (at the junction of the volar and dorsal skin markings) to 3 to 5 mm distal to the distal interphalangeal joint. The tip of the knife blade is inserted just under the bone to a depth corresponding to the opposite edge of the distal phalanx-- slightly more than halfway across the volar surface of the finger. A hemostat is inserted into the incision and is spread in the plane of the fingernail (perpendicular to the septa) to break open remaining septa and loculations. Necrotic tissue or any foreign matter is excised under direct vision, and the wound is irrigated. A small gauze pack is placed in the incision. Because the incision may produce partial numbness of the fingertip by associated digital nerve injury, the incision should not be made on the radial aspect of the index finger or the ulnar aspect of the thumb or little finger.
An acceptable alternative to the hockey-stick, or median, incision is the through-and-through incision (Fig. 40-22) . This is basically a hockey stick-type incision (without the curved distal portion of the "hockey stick") that is carried through to the opposite side of the finger. A hemostat is used to break up loculations, and a rubber drain (Penrose) is placed through the incision for continual drainage. The through-and-through incision is probably the easiest procedure for most felons.
The fishmouth, or horseshoe, incision is basically 2 hockey-stick incisions that meet at the tip of the finger. A gauze pack is placed between the flaps and should be removed in a few days. This is a rather radical procedure but allows complete visualization and debridement of necrotic tissue (Fig. 40-23) . Some physicians advise against this incision, because it is extensive and may take a long time to heal. In addition, it produces a sizable scar and an unstable finger pulp. The fishmouth incision may be used if more conservative incisions are not successful, but it is not recommended for use initially.
No matter which incision is made, it must not be carried proximal to the closed pulp space because of the danger of entrance into the tendon sheath or the joint capsule. The patient should be rechecked in 2 to 3 days. A snug dressing, splinting and elevation, and adequate opioid analgesics are prerequisites for a successful outcome and a happy patient.
On the first postoperative visit, a digital block may again be performed and any packing removed. The incision is irrigated copiously with saline, and any additional necrotic tissue is removed. At this time, the drain may be replaced for 24 to 48 hours if there is continued drainage, but usually it can be removed and a dressing reapplied. Soaking may be advised. At the first revisit, the sensitivities of the bacterial cultures are checked, and a decision to continue or change antibiotics is made. Most felons are empirically treated with antibiotics for at least 5 days. A broad-spectrum cephalosporin is a reasonable choice, pending cultures (if done).
A few additional points should be emphasized at this time. Frank pus may be encountered during incision, but usually only a few drops are expressed. One more often drains a combination of necrotic tissue and interstitial fluid. A careful search for a foreign body should be made even if the history is not known. Some physicians advocate radiographic evaluation for retained foreign bodies and a baseline evaluation of the bone for subsequent evaluation of osteomyelitis at the initial visit. Other physicians will reserve radiographs for wounds not showing significant improvement in 5 to 7 days. Evidence of osteomyelitis, however, may not be found radiographically for several weeks after the appearance of the lesion. More radical incision and drainage may be required in persistent infections. Following adequate drainage, osteomyelitis may respond surprisingly well to outpatient antibiotic therapy with almost complete regeneration of bone if incision and drainage have been adequate. Persistent cases may require IV antibiotics.
Resistant fingertip infections are not uncommon. Difficult or persistent cases require evaluation and care by a hand surgeon. In these cases, early consultation is advisable to avert catastrophic complications such as loss of function or amputation.
Subungual hematoma is an injury that is frequently seen in the ED. Any digit may be affected. The hematoma often results from hitting the fingertip with a hammer or slamming it in a door. The main concern of the patient is relief of the terrible throbbing pain that accompanies the condition as the pressure of the hematoma increases. Pain relief can be accomplished quickly with nail trephination. Trephination may be performed with a large paper clip that has been heated until it is red hot. The instrument is applied to burn a hole at the base of the nail (Fig. 40-24) . Blood rapidly exits, and the blackened nail regains its normal color (Fig. 40-25) . The blood usually remains fluid for 24 to 36 hours and is easily expressed with slight pressure. Care should be taken to make multiple holes or a single hole that is large enough to allow continued drainage. An oversized paper clip is the simplest apparatus. Although a portable hot-wire electrocautery unit is available and is frequently recommended, it is difficult to obtain an adequate drainage hole without adapting the instrument and its use. One can modify the electrocautery device to burn a larger hole by "fattening" the end of the wire loop and rotating the device slowly as the nail is penetrated or by removing a small rectangle of nail with the cautery device. In addition to being convenient, the cautery device is desirable because the wire stays hotter longer, thus enhancing nail penetration. In the stoic patient, no anesthesia may be necessary, but a digital block affords painless trephination, and its routine use is suggested with the anxious patient.
The majority of subungual hematomas are painful but minor injuries. Complicated cases involve fractures of the distal phalanx. When the fingertip is unstable or the mechanism of injury suggests a significant distal phalanx fracture, a radiograph should be obtained. If a significant fracture is present, the digit should be splinted. A distal phalangeal fracture with a subungual hematoma is technically an open (compound) fracture. Such injuries usually heal without problems, although osteomyelitis of the tuft is a theoretical complication. The value of routine antibiotic prophylaxis in such cases is unproved, and their use is not standard in minor cases but may be of value in significant crush injuries. The presence of an underlying fracture does not contraindicate nail trephination for fear of changing closed fracture into an open one. It is difficult to predict the fate of the fingernail following drainage of a subungual hematoma. Some patients with subungual hematomas will lose the nail, but if the nail root or nailbed is not significantly disrupted and the nail remains implanted, a normal-appearing nail is the usual final result. If the nailbed is significantly lacerated or the edges of the nail are unstable, the nail should be removed and the nailbed repaired (see further discussion in Chapter 37) . Patients should be informed of possible future cosmetic problems.
The editors and author wish to acknowledge the significant contributions of Todd M. Warden and Mark W. Fourre to this chapter in previous editions.