Bacteriology of Cutaneous Abscesses

Although most abscesses contain bacteria, 5% of abscesses are sterile, especially those associated with IV drug use. Clinically, sterile abscesses cannot be differentiated from those caused by bacteria. Somewhat atypical abscesses develop in parenteral drug users. Injection of a cocaine-heroin mixture (“speedball”) may predispose users to abscesses by inducing soft tissue ischemia.¹¹ Bergstein and coworkers⁹ found anaerobes in 143 of 243 isolates from 57 drug-abusing patients. Abscesses at the site of injection tend to contain predominantly staphylococcal and streptococcal species. However, some drug users lubricate their hypodermic needles with saliva, which potentially explains the isolation of oral pathogens such as Eikenella corrodens from injection site abscesses.

The microbiology and the underlying cause of skin and soft tissue abscesses are related to their location. Abscesses involving the extremities are generally the result of a breach in the skin’s integrity from trauma such as cuts, abrasions, or needle punctures. Abscesses involving the head, neck, and perineal region are usually associated with obstruction of the apocrine sweat glands. These types of abscesses increase in frequency after puberty because of the increased apocrine and sebaceous gland activity. Perirectal abscesses are typically the result of bacterial spread from adjacent anal glands. Vulvovaginal abscesses usually result from obstruction of a Bartholin gland, which then causes duct and gland edema and subsequent infection. Pilonidal abscesses are hypothesized to be caused by sacrococcygeal infections from ingrown hairs in the intergluteal cleft.

In 2002, Brook¹² compiled the findings from more than 15 bacteriologic studies of 676 polymicrobial abscesses. S. aureus and group A β-hemolytic streptococci were the most prevalent aerobes in skin and soft tissue abscesses and were isolated in specimens from all body sites. Gastrointestinal and cervical flora (enteric gram-negative bacilli and Bacteroides fragilis) were found most often in intraabdominal, buttock, and leg lesions. Group A β-hemolytic streptococci, pigmented Prevotella, Porphyromonas species, and Fusobacterium species—all normal residents of the oral cavity—were most commonly found in lesions of the mouth, head, neck, and fingers.

In a study of the bacteriology of cutaneous abscesses in children, Brook and Finegold¹³ found aerobes (staphylococci and group A β-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 was found in the perirectal area, head, fingers, and nail bed. This study noted an unexpectedly high incidence of anaerobes in nonperineal abscesses. Anaerobes were found primarily in areas adjacent to mucosal membranes (e.g., the mouth), where these organisms tend to thrive, and in areas that are easily contaminated (e.g., by sucking fingers, which causes nail bed and finger infections or bite injuries).

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. For example, tuberculosis or fungal isolates are sometimes found in immunocompromised patients (e.g., those with diabetes or acquired immunodeficiency syndrome). Finding Escherichia coli suggests an enteric fistula or even self-inoculation of feces in some patients with a psychiatric illness such as Munchausen’s syndrome. Recurrent abscesses without an obvious underlying cause could indicate clandestine drug use. What appears to be a typical recurrent abscess may be a manifestation of an underlying septic joint, osteomyelitis, or rarely, metastatic or primary cancer (Fig. 37-2).

Special Considerations

Parenteral drug users, insulin-dependent diabetics, hemodialysis patients, cancer patients, transplant recipients, and individuals with acute leukemia have an increased frequency of abscess formation when compared with the general population. At initial evaluation the patient may emphasize an exacerbation of the underlying disease process or an unexplained fever, with symptoms of an abscess being a secondary complaint. In this situation, abscesses tend to have exotic or uncommon bacteriologic or fungal causes and typically respond poorly to therapy.14–17 Patients with diabetes-induced ketoacidosis (DKA) should be evaluated extensively for an infectious process; a rectal examination should be included with the physical examination to rule out a perirectal abscess as the infectious trigger of DKA. This is also true for patients who are immunocompromised. There are several reasons why patients with diabetes and parenteral drug users are at increased risk for abscess formation: intrinsic immune deficiency, an increased incidence of staphylococcal carriage, potentially compromised tissue perfusion, and frequent needle punctures, which allow a mode of entry for pathogenic bacteria.¹⁸

Drug users frequently use veins in the neck and in the femoral areas, which can produce abscesses and other infectious complications at these sites.¹⁹ Any abscess near a vein of the antecubital fossa or dorsum of the hand should alert the clinician to possible IV drug use; however, substance users may also inject directly into the skin (“skin popping”), which can cause cutaneous abscesses distant from veins (Fig. 37-3).

A foreign body may serve as a nidus for abscess formation. IV drug users frequently break needles off in skin that has been toughened by multiple injections, so 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, consider radiographs or other techniques to search for foreign bodies, an underlying septic joint, or osteomyelitis.²⁰ Ultrasound is also a useful adjunct to evaluate for foreign bodies that are not radiopaque.

MRSA

First acknowledged in the 1960s as a cause of infection in patients in health care settings, MRSA has now become the most common identifiable cause of community-acquired skin and soft tissue infections in many metropolitan areas in the United States. The spread of this organism is considered an epidemic, and it is a very virulent and aggressive.21,22

Virulent community-acquired MRSA (CA-MRSA) causes rapid and destructive soft tissue infection because of the presence of two bacterial toxins elaborated by the omnipresent VSA-300 and VSA-400 strains. Panton-Valentine leukocidin enhances tissue necrosis, and phenol-soluble modulin is toxic to neutrophils. A small pustule can become a large abscess in 24 to 48 hours (Fig. 37-4). Such lesions are often mistaken for a spider bite or drug use because of their rapid progression and seemingly spontaneous onset in an otherwise healthy person. Methicillin resistance is mediated by PBP-2a, a penicillin-binding protein encoded by the mecA gene that permits the organism to grow and divide in the presence of methicillin and other β-lactam antibiotics. S. aureus acquires methicillin resistance through a mobile staphylococcal cassette chromosome (SCC) that contains the mecA gene complex (SCCmec). MRSA probably arose as a result of antibiotic selective pressure.^23,24

A single clone probably accounted for most MRSA isolates discovered during the 1960s; by 2004, six major MRSA clones had emerged.²⁵ The spread of resistance is thought to be mediated by horizontal transfer of the mecA gene and related regulatory sequences thereon.²⁶

In 1980, the spread of MRSA from hospitals into communities became evident. More recently, community-acquired infections have occurred more frequently, even in people without known risk factors. These observations have led to the identification of some risk factors for CA-MRSA (Box 37-1), including skin trauma (e.g., lacerations, tattoos, IV and intradermal drug use, shaving), incarceration, shared razors or towels, and close contact with others colonized or infected with MRSA.^27–35 Animals can also carry MRSA and can function as a source of transmission.³⁶ Importantly, many patients with CA-MRSA have no identifiable risk factors for acquisition of the disease.³⁷

CA-MRSA tends to be more virulent than health care–associated MRSA (HA-MRSA) and is associated with more frequent serious complications such as osteomyelitis, joint infections, sepsis, and death. However, these organisms fortunately tend to be susceptible to a broader array of antibiotics.³⁸

The prevalence of MRSA has increased in both health care and community settings. For example, the prevalence of methicillin resistance among S. aureus isolates in intensive care units in the United States was 60%,²¹ and more than 90,000 invasive infections by MRSA occurred in the United States in 2005.³⁹

HA-MRSA and CA-MRSA differ with respect to their clinical epidemiology and molecular structures.

HA-MRSA is defined as MRSA infection that occurs following hospitalization (hospital onset, formerly “nosocomial”) or MRSA infection that occurs outside the hospital within 12 months of exposure to a health care setting (e.g., history of surgery, hospitalization, dialysis, or residence in a long-term care facility—community onset instead of community acquired).²¹

HA-MRSA is usually associated with severe, invasive disease, including skin and soft tissue infection, bloodstream infection, and pneumonia.6,40 In fact, S. aureus continues to be a significant cause of surgical site infections.³⁹ HA-MRSA strains tend to be resistant to multiple drugs. MRSA is one of the few pathogens routinely implicated in nearly every type of hospital-acquired infection. This is probably related in part to the organism’s capacity for biofilm formation on indwelling lines and tubes in hospital settings.²⁴

Biofilm facilitates survival and multiplication of MRSA on these surfaces, thereby prolonging the duration of exposure of the organism to antibiotics, as well as promoting the potential for the development of genetic resistance.²⁷

CA-MRSA is defined as MRSA infection that occurs in the absence of health care exposure. It is often associated with skin and soft tissue infections in young, otherwise healthy individuals.²⁷

Most CA-MRSA strains are sensitive to non–β-lactam antibiotics, although a multidrug-resistant isolate has been described in men who have sex with men.41,42 This strain contains the pUSA03 plasmid and carries resistance genes for β-lactams, fluoroquinolones, tetracycline, macrolides, clindamycin, and mupirocin.

The CA-MRSA and HA-MRSA classifications are no longer distinct since MRSA colonization can develop in one realm and manifestations of infection in another. In the mid-2000s in San Francisco, the annual incidence of CA-MRSA surpassed that of HA-MRSA.⁴³

Furthermore, community-onset HA-MRSA infections have been observed with increasing frequency. This was illustrated in a study of 209 patients discharged from hospitalized care; within 18 months following hospital discharge, 49% of new MRSA infections began outside the hospital.⁴⁴

In another series of 102 patients with CA-MRSA infections, 29% had molecular typing consistent with HA-MRSA.⁴⁵

CA-MRSA was initially reported in injection drug users in the early 1980s and has since become the most frequent cause of skin and soft tissue infections seen in U.S. EDs and ambulatory clinics. In an assessment of the prevalence of MRSA across the United States, Moran and colleagues⁴⁶ compiled data from adults who sought treatment of acute skin and soft tissue infections in EDs in 11 American cities in August 2004. S. aureus was isolated from three fourths of the 422 patients who met the study criteria. Seventy-eight percent of the S. aureus isolates were resistant to methicillin. MRSA was isolated from 59% of patients in the study. The prevalence of MRSA ranged from 15% to 74% in the participating EDs (Table 37-1). MRSA was the most common identifiable cause of skin and soft tissue infections in all but one of the EDs.

Frazee and associates,³⁸ reporting from an ED in northern California, found that half of the 137 patients in their study were either infected with or colonized by MRSA. Three fourths of all S. aureus isolates were MRSA. In addition, 76% of cases met a strict clinical definition of CA-MRSA.

The incidence of CA-MRSA, genetically unrelated to nosocomial isolates, increased steadily from 1990 to 2001 and then dramatically in 2002 and each year thereafter.47,48

MRSA has also emerged as a potential sexually transmitted disease. Roberts and colleagues described their treatment of two patients who came to their urban ED with abscesses probably transmitted by heterosexual oral-genital contact. Both tested positive for MRSA.²² A 2010 case report drew a similar conclusion. It reported orogenital transmission of MRSA to an immunocompetent 22-year-old man who tested orally positive for MRSA and group B (genital) Streptococcus after oral contact with a female partner in whom MRSA-positive gluteal lesions had previously been diagnosed.⁴⁸

In a retrospective chart review, Roberts and colleagues found that 18% of the 524 subcutaneous abscesses treated in their urban ED in 2006 were confined to the genital area. Almost three fourths of the 272 outpatient wound cultures performed on that year’s patient population were positive for MRSA.²²

Ultrasound-Guided Needle Aspiration

Radiologists have performed needle aspiration of abscesses for some time, and emergency clinicians are now becoming more comfortable with the procedure. High-resolution ultrasound technology is being used to obviate “blind” procedures done in the ED (e.g., joint aspiration and central line placement).

For ultrasound-guided drainage of a cutaneous abscess, use a high-resolution probe (5 or 7.5 MHz), and maintain sterility throughout the procedure. Place the sterile transducer over the main body of the abscess, and insert the needle through the skin adjacent to the transducer. Adjust their relative relationships in keeping with the depth and location of the abscess cavity. Guide the needle—seen as a bright artifact—directly into the abscess. Watch the abscess cavity collapse as pus drains out. Scan the entire area of the suspected abscess to capture unexpected extensions. Be sure to drain all pockets.

Therapeutic Antibiotics

In contrast to prophylaxis before surgery, the routine use of therapeutic oral antibiotics after I&D of simple cutaneous abscesses in otherwise healthy patients who are not immunocompromised appears to have no value, and their empirical use cannot be scientifically supported. Llera and Levy⁵² performed a randomized, double-blind study to compare the outcomes of patients treated with a first-generation cephalosporin after the drainage of cutaneous abscesses in the ED with those who received placebo. They found no significant difference in clinical outcome between the two groups and concluded that antibiotics are unnecessary for abscesses in individuals with normal host defenses. This is in agreement with several previous studies.^54–56 It should be noted that high-risk patients were often excluded from these studies. Immunocompromised patients have not been adequately studied in this situation and are therefore often given antibiotics empirically, but this practice, though common, has not been supported by rigorous prospective studies.

For empirical coverage of CA-MRSA in outpatients with skin and soft tissue infection, oral antibiotic options include the following: clindamycin, trimethoprim-sulfamethoxazole (TMP-SMX), a tetracycline (doxycycline or minocycline), and linezolid. If coverage of both β-hemolytic streptococci and CA-MRSA is desired, options include the following: clindamyacin alone or the use of TMP-SMX or a tetracycline in combination with a β-lactam (e.g., amoxicillin or cephalexin), or linezolid alone. The use of rifampin as a single agent or as adjunctive therapy for the treatment of skin and soft tissue infections is not recommended.

Facial abscesses should be handled cautiously and checked frequently. Any abscess above the upper lip and below the brow may drain into the cavernous sinus, so manipulation may predispose to septic thrombophlebitis of this system. Treatment with antistaphylococcal antibiotics and warm soaks after I&D 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.

A relatively unstudied but a common and currently accepted strategy for patients with soft tissue infections (especially CA-MRSA infections) that are borderline, by clinical judgment, for hospital admission and therapeutic IV antibiotics is to administer a single dose of an IV antibiotic in the ED, followed by oral antibiotics and close outpatient follow-up. When a CA-MRSA infection is likely, IV vancomycin or linezolid is a reasonable option. Oral linezolid may be as effective as the IV form.

Prophylactic Antibiotics

Procedure Setting

Definitive I&D of soft tissue abscesses is performed in either the ED or the operating room (OR). When abscesses are drained in the ED, some centers prefer to use a special area to avoid contamination of general treatment rooms, but protocols vary greatly.

The choice of the locale for the procedure depends on a number of important factors. The location of the abscess may dictate management in the OR. Large abscesses or abscesses located deep in soft tissues require a procedure involving a great degree of patient cooperation, which might be achieved only 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 factor limiting I&D in the ED. The current increased use of ED procedural sedation (see Chapter 33) has changed previous OR cases to ones that can be managed well in the ED. If the clinician believes that 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.

Equipment and Anesthesia

A standard suture tray provides adequate instruments if a scalpel and packing material are added (Fig. 37-5). Although sterility is impossible during the procedure, one should avoid contamination of surrounding tissue. Some clinicians prefer to use an obligatory skin scrub with an antiseptic solution, but the value of this step is dubious. Most clinician use nonsterile gloves while draining pus, but practice varies.

It is often quite difficult to achieve local anesthesia by direct infiltration because of the poor function of local anesthetic agents in the low pH of infected tissue. Furthermore, 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 cannot generally be achieved. If a regional block can be performed (see Chapters 30, 31, and 32), 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 therefore absorbed quickly. Strict adherence to maximum safe doses of local anesthetics is required.

The skin over the dome of an abscess is often quite thin, thus making skin anesthesia difficult. If a 25-gauge needle is used carefully, one can frequently inject the dome of the abscess subcutaneously. Without moving the tip of the needle, the anesthetic solution spreads over the dome through the subcutaneous 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. 37-6, step 2). In an extremely anxious or uncomfortable patient, judicious use of preoperative sedation (see Chapter 33) with IV opioids and sedatives or with nitrous oxide makes the procedure easier for both the patient and clinician. Ketamine, propofol, or a combination of these drugs is a popular option in the ED setting.

Some clinicians recommend the use of topical ethyl chloride or Fluori-Methane spray for the initial skin incision, but although this is an attractive concept to patients, the pain relief offered by these agents is variable and fleeting. Ethyl chloride is also highly flammable. These vapocoolant sprays may be useful to provide momentary anesthesia for injection of a local anesthetic or for the initial skin incision if the injection or incision is made immediately after blanching of the skin. In general, however, these agents are of minimal benefit as a stand-alone anesthetic agent for all but the smallest of superficial abscesses (e.g., purulent folliculitis).

Incision

One should make all incisions conform with skin creases or natural folds to minimize visible scar formation (Fig. 37-7). Care should be taken in areas such as the groin, the posterior aspect of the knee, the antecubital fossa, and the neck so that vascular and neural structures are not damaged.

A No. 11 or 15 scalpel blade, held perpendicular to the skin, 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. 37-6, step 3). This will afford more complete drainage and facilitate subsequent breakup of loculations. Attempting to drain an abscess with an inadequate incision is counterproductive and makes packing changes more difficult. A cruciate or X-shaped incision and an elliptical skin excision are to be avoided in the routine treatment of cutaneous abscesses. The tips of the flaps of a cruciate incision may necrose and result in an unsightly scar (Fig. 37-8). A timid “stab” incision may produce pus but is not generally adequate for proper drainage. The scalpel is used only to make the skin incision and is not used deep in the abscess cavity.

Exceptions to the rule regarding aggressive incision are abscesses in cosmetic areas, in areas under significant skin tension (e.g., extensor surfaces), and in areas with extensive scar tissue (e.g., sites of multiple previous drainage procedures). In these special circumstances, a stab incision or simple aspiration alone may be attempted initially, 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 I&D may be required. The abscess will need to be reassessed in 24 to 48 hours to determine whether additional intervention is needed.

Wound Dissection

Following a standard incision, the operator should probe the depth of an abscess to assess its extent and ensure proper drainage by breaking open loculations (see Fig. 37-6, step 5). An ideal instrument for this procedure is a hemostat, optionally wrapped in gauze (or a cotton swab for small abscesses), which is placed into the abscess cavity and spread and manipulated throughout the cavity (Fig. 37-9). 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 an abscess caused by skin-popping of IV drugs. These abscesses occasionally harbor broken needle fragments (see Fig. 37-9D and E). In addition, patients who engage in this practice have a high incidence of hepatitis and HIV infection. Clinicians are often surprised at the depth or extent of abscesses discovered during probing. Sharp curettage of the abscess cavity is not usually required and may produce bacteremia. Although tissue probing is generally the most painful aspect of the technique and total local anesthesia is difficult to attain, this portion of the procedure should not be abbreviated. If pain persists, additional local anesthetic can be administered through the cut skin edges and into deeper tissues to provide additional anesthesia (Fig. 37-10A). If the procedure is limited because of pain, use of appropriate analgesia or anesthesia is mandated. Failure to adequately pack the abscess on the first visit makes follow-up packing changes more problematic.

A blunt-ended suction device can be used to extract copious pus from large or deep abscesses while also assisting in breakup of loculations (see Fig. 37-10B).

Wound Irrigation

Following the breakup of loculations, some clinicians advocate copious irrigation of the abscess cavity with normal saline to ensure adequate removal of debris from the wound cavity (see Fig. 37-6, step 6). Though intuitively beneficial, irrigation of the abscess cavity is not universal and has not been experimentally demonstrated to significantly augment healing or affect outcome. Hyperemic tissue may bleed profusely, but the bleeding usually stops in a few minutes if packing is used. Abscesses of the extremities can be drained with the use of a tourniquet to provide a bloodless field.

Packing and Dressing

Multiple studies, most from countries outside the United States, suggest that primary suture closure of incised and drained abscesses results in faster healing than after packing and secondary closure and in similar low abscess recurrence rates. Many of the reported cases involved abscesses in the anogenital region, a site teeming with bacteria. Acute superficial abscesses can be cured with incision, curettage, and primary suture closure without antibiotics or packing, which is safe and cost-effective. This clinical approach is not currently in wide practice in the United States.

Although the specific technique and the clinical value of routine packing of abscesses have not been well studied, packing is a traditional intervention and is often performed in the ED. Some, however, advocate that packing is not needed nor beneficial for easily drained abscesses, and the intervention adds to cost and patient discomfort. As noted above, some advocate curettage and irrigation of the abscess cavity and then primary suture closure, without packing. Overall, it appears reasonable to avoid packing of small, easily drained abscesses. The loop drainage technique described below is evidence that formal packing is not a prerequisite for abscess healing. Hence, clinical judgment, common sense, and individualized treatment based on the particular scenario should prevail. Simple stated, no packing standard is universally accepted.

When used, 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 (see Fig. 37-6, step 7). The packing material should make contact with the cavity wall so that on removal, gentle débridement of necrotic tissue will occur spontaneously. 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 saline or povidone-iodine, and some use gauze impregnated with iodine (iodoform). For large abscess cavities, gauze pads (without cotton backing) are ideal packing material (Fig. 37-11). 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. Packing, especially packing strips containing iodine, will be radiopaque on a plain radiograph. If a foreign body is considered, a radiograph should be obtained before packing. 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 (see Fig. 37-6, step 8). 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 and 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.

After treatment, packing is often changed periodically (Fig. 37-12A). Most patients require a repeated visit to the clinician for packing change, but if the original packing is to be removed and not replaced (as with a paronychia or hair follicle abscess), selected patients may remove the packing and perform their own wound care totally at home. Motivated patients can provide total follow-up, and a cotton-tipped applicator swirled in the base of the wound for a few days can replace formal packing (see Fig. 37-12B).

Folliculitis, Furuncles, and Carbuncles

Folliculitis, furuncles, and carbuncles can develop in healthy individuals with no predisposing risk factors other than skin, nasal, perineal, or gut colonization with a Staphylococcus bacterium. The umbilicus of neonates is also commonly colonized. Individuals in close contact with others who have active disease in the form of abscesses, furuncles, or carbuncles are at increased risk for similar infections. The pathogenesis of staphylococcal disease is a complex host-bacterium interaction. S. aureus invades the skin by way of the hair follicles or an open wound (abrasions, shaving, or insect bites) 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 distant organs. Most cases of staphylococcal osteomyelitis, meningitis, and endocarditis occur by this mechanism.2,69

Folliculitis represents inflammation of hair follicles in response to infection, chemical irritation, or skin injury (Fig. 37-14A). An area of purulence often forms after superficial bacterial invasion of the hair follicle and is generally isolated to the epidermis. S. aureus is commonly found, although other bacteria are also responsible for specific follicular infections. Pseudomonas is an important pathogen in cases caused by exposure to hot tubs, pools, or whirlpools that are not adequately chlorinated.⁴ In persons with broad-spectrum antibiotic use or immunosuppression, consider Candida as well.⁷⁰ Individuals exposed to whirlpool foot baths at nail salons are at risk for mycobacterial infection. Treatment generally involves local measures, including warm compresses, antibacterial soaps and ointments, and avoidance of the source of contaminated water in the case of hot tub or whirlpool footbath folliculitis. These measures usually suffice, but systemic antibiotics may be required if multiple sites are involved or if the patient is a chronic staphylococcal carrier. Shaving of involved areas should be temporarily avoided.

Furuncles, or boils, are acute circumscribed abscesses of the skin and subcutaneous tissue that usually involve the hair follicle (see Fig. 37-14B). They most commonly occur on the face, neck, buttocks, thigh, perineum, breast, and axilla. Carbuncles are aggregates of interconnected furuncles that frequently occur on the back of the neck (see Fig. 37-14C). In this area the skin is thick, so extension occurs laterally rather than toward the skin surface. S. aureus species, both methicillin susceptible and methicillin resistant, are the usual culprits.⁴⁰ Carbuncles may become large and can cause systemic symptoms and complications. All patients with a carbuncle should be evaluated for diabetes because this is a common risk factor. Treatment should consist of surgical drainage and administration of systemic antibiotics. Large carbuncles may be difficult to drain adequately in the ED and could require operative management. Carbuncles usually consist of many loculated pockets of pus, so simple I&D is often not curative. Occasionally, wide excision and skin grafting are required.

Most recurrent staphylococcal skin infections are caused by autoinfection from skin lesions or nasal reservoirs. Prevention is directed at eliminating the organism. This is accomplished by the application of bacitracin to the nares, chlorhexidine baths, and good hygiene, including frequent cleansing with antibacterial soap. If these measures are unsuccessful, systemic oral antistaphylococcal treatment is instituted for 2 to 3 weeks. Detection and treatment of infection in family members may be necessary.2,71,72

S. aureus can cause suture abscesses. A suture abscess is often misdiagnosed as a wound infection, but in fact it is a local nidus of inflammation, infection, or both caused and potentiated by suture material. Such an abscess usually appears after sutures have been in place for 3 to 5 days, with single or multiple discrete areas of erythema and tenderness being noted at the site where the suture penetrates the skin. Simply removing the suture (a drop of pus may be expressed) and providing warm compresses and topical antibiotic ointment is generally 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 the wound with a small hook or bent needle (see Chapter 35) to snare the suture for removal.

Hidradenitis Suppurativa

Hidradenitis suppurativa (Greek hidros, or “sweat,” and aden, or “gland”) is a chronic, relapsing, inflammatory disease process that affects the apocrine sweat glands in the axilla, the inguinal region,⁷³ and the perineum (Fig. 37-15). Its prevalence is 0.3% to 4% in industrialized countries; most affected individuals are young women.⁷⁴ The condition results from follicular inflammation and subsequent occlusion of the apocrine ducts by keratinous debris, which leads to ductal dilation, inflammation, and rupture into the subcutaneous area. Most commonly, the disease is manifested as an episodic appearance of localized pain, edema, pruritus, burning, swelling, and purulence. Dysregulation of the immune response is thought to play a role, with some studies showing a response to immunosuppressive agents.⁷⁵ Occlusion of the hair follicle predisposes to secondary bacterial infection and subsequent abscess formation. In its early stages it is indistinguishable from a simple furuncle. Progression and recurrence, however, lead to the distinctive appearance of multiple foci coupled with areas of induration and inflammation that are in various stages of healing. This chronic process can create draining fistulous tracts, often involving large areas that are not amenable to simple I&D procedures (see Fig. 37-15C).⁷²

Genetic factors may play some role in hidradenitis suppurativa.⁷⁶ Fitzsimmons and Guilbert⁷⁷ proposed a single dominant gene transmission. Some authors have suggested an increased incidence in patients of African descent, although this does not seem to be substantiated by studies.⁷⁸ A hormonal association has also been postulated. More women than men are affected, and onset after menopause and before puberty is rare.⁷⁹ Other factors thought to be related include obesity and smoking. A matched-pair case-control study found an odds ratio of 9.4 in smokers versus controls (95% confidence interval, 3.7 to 23.7).⁸⁰ Environmental factors, including antiperspirants and shaving,⁸¹ were implicated in the past, but more recent studies have not found any association.⁸²

Bacterial cultures of specimens from suppurative hidradenitis lesions are frequently sterile or reflect organisms seen in other soft tissue abscesses. Staphylococcus is the most commonly isolated organism,⁸² with E. coli and β-hemolytic streptococci 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 cultured. CA-MRSA is an increasing cause of such abscesses.

Initial outpatient management of an acute suppurative lesion usually involves ED intervention. Any fluctuant area requires drainage, as described in the section “I&D Procedure.” In patients with extensive cellulitis, a broad-spectrum, antistaphylococcal antibiotic should be used. Unfortunately, hidradenitis suppurativa cannot be cured with localized I&D. If I&D is required for relief of a secondary abscess, it should be made clear to the patient that this procedure does not cure the underlying disease.⁸³ The chronic nature of the disease produces multiple areas of inflammation and subcutaneous fistulous tracts that induce routine recurrences. The patient must be informed of this 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 only limited degrees of success. Few controlled studies of treatment strategies have been performed. Patients are often counseled to lose weight, stop smoking, 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.⁸⁴ Retrospective reviews looking at the efficacy of combination therapy (clindamycin and rifampin) have been promising, with some patients experiencing long-term remission, although diarrhea is a common side effect.^85,86 There have been reports of success with topical clindamycin,^87,88 hormone therapy in females,⁸⁹ and laser therapy.⁹⁰ Finally, immunosuppressive therapy with tumor necrosis factor-α inhibitors (infliximab, adalimumab^91,92) has been successful in treating a few intractable cases.

Advanced stages of the disease are managed by wide or local excision. Smaller excisions are more likely to recur than wider excisions.⁹³ Delayed closure^94,95 may offer better results, but this has not been directly compared with primary closure. Wide excision may warrant skin grafting.⁹⁶

Breast Abscess

Breast abscesses can occur in lactating (14%) and nonlactating breasts (86%).⁹⁷ They are caused by normal skin bacteria that enter through a break or crack in the skin, usually the nipple (Fig. 37-16). The infection becomes established in parenchymal tissue and causes pain, swelling, and localized hyperthermia. In its early stages, when cellulitis predominates, a breast abscess can be difficult to diagnose. In equivocal cases, antibiotics may be curative. Cellulitis may progress to frank abscess formation. Women with this condition can be quite ill and appear toxic.

The estimated incidence of inflammatory processes of the breast (mastitis) in lactating women ranges from 2% to 33%.⁹⁸ In lactating women the infection is usually precipitated by milk stasis after weaning or missed feedings and usually occurs in the first 6 weeks of breastfeeding or during the weaning phase. The cause is usually bacterial invasion through a cracked or abraded nipple by S. aureus, including MRSA, or streptococci originating from the mouth of the nursing child.^99–101 Manifestations include 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.¹⁰²

Breast abscesses in nonlactating women are more common. People at risk are smokers and diabetics. These are also risk factors for recurrence. In addition, abscesses may be a complication of nipple piercing or breast implants inserted under appropriate medical care,¹⁰³ as well as via illicit cosmetic procedures.^104,105 In nonpuerperal infections, S. aureus and streptococci are common causative organisms, as are Bacteroides species and anaerobic streptococci.¹⁰⁵ Mixed flora are more commonly found in recurrent abscesses (20.5% in those with recurrence versus 8.9% in those with a single episode).¹⁰⁶ Recommended antibiotics include amoxicillin and clavulanic acid or, in patients with penicillin allergies, combination therapy with erythromycin and metronidazole. If the community prevalence of MRSA is high, treatment with clindamycin, tetracycline, or TMP-SMX should be considered.¹⁰⁷

Ultrasound-guided needle aspiration is becoming the standard of care for most breast abscesses. When compared with I&D, aspiration causes less scarring, does not interfere with breastfeeding, and does not require procedural sedation.¹⁰⁷ Christensen and associates¹⁰⁸ recommended that ultrasound-guided needle drainage replace surgery as first-line treatment of uncomplicated puerperal and nonpuerperal breast abscesses. Emerging treatment parameters are ultrasound-guided needle aspiration for abscesses less than 3 cm in diameter and ultrasound-guided catheter drainage for abscesses 3 cm in diameter or larger.¹⁰⁹ Ultrasound images of breast abscesses appear as inhomogeneous, hyperechoic masses (Fig. 37-17). Repeat aspiration every other day to achieve complete resolution, with a mean of 3.5 aspirations being required.¹⁰⁹

Recurrent abscesses are a common, troublesome complication after traditional treatment with I&D and antibiotics.110,111 Fortunately, the reported recurrence rate associated with ultrasound-guided aspiration or drainage procedures is quite low.^112,113 Patients with persistent recurrences should be managed by a surgeon for total excision of the involved area.

Although a breast abscess is rarely a harbinger of malignancy, it could be the initial manifestation of a metastatic process.112,114 After needle aspiration or catheter drainage, send the aspirate for culture and cytologic examination, and perform a postdrainage mammogram and ultrasound to evaluate for underlying or coexistent malignancy.¹¹³

A breast abscess in a male is an unusual occurrence, so consider malignancy and underlying bone or joint infection in these cases (see Fig. 37-2A and B).

Bartholin Gland Abscess

The Bartholin glands (or greater vestibular glands) are located at the 4- and 8-o’clock positions on each side of the vestibule of the vagina (Fig. 37-18A). These mucus-secreting glands maintain the moisture of the vaginal mucosa. When the ostium becomes blocked by inflammation or trauma, a cyst or abscess may form, which occurs in 2% of women.¹¹⁵

Asymptomatic cysts (no pain, no discharge) frequently occur as a result of duct blockage and retention of secretions. Symptomatic cysts (vulvar pain, dyspareunia, and discomfort while walking or sitting) can be managed with warm sitz baths and compresses. Abscesses involve an acute inflammatory reaction within the stroma of the duct and are usually accompanied by pain, rubor, and occasionally discharge. The majority of cases (80%) are caused by mixed vaginal flora (Bacteroides, E. coli, S. aureus).¹¹⁶ Neisseria gonorrhea and, less commonly, Chlamydia can also be involved. Examination reveals a tender, fluctuant mass in the posterior of the labia that can be palpated between the thumb and index finger (see Fig. 37-18B).

The most common procedure for treating a Bartholin abscess is insertion of a drainage catheter, as described by Word in 1968.¹¹⁷ This single-barreled, sealed-stopper, balloon-tipped catheter serves as initial and long-term therapy (Fig. 37-19A). In his original description, Word reported only 2 recurrences in 72 lesions, both of which were treated successfully with a second catheter. None of the patients required marsupialization. The Word catheter procedure involves fistulization of the duct cavity by a 1-inch catheter with an inflatable balloon tip.¹¹⁸ Though not a traditional I&D procedure, the technique permits continued drainage of the gland.

In preparation for insertion of the catheter, place the patient in the standard dorsal lithotomy position and drape the perineum (Fig. 37-20, step 1). Cleanse the area with povidone-iodine solution. If an anesthetic is deemed necessary for patient comfort and cooperation, infiltrate with lidocaine just external to the hymenal ring, where the distal duct opening should be located (at the 5- or 7-o’clock position) (see Fig. 37-20, step 2).¹¹⁹ Test the balloon of the Word catheter by filling it with 3 mL of water via a 25-gauge needle. Aspirate the water back and keep the needle on the catheter to serve as a handle for insertion. Make a small incision in the mucosa, not the cutaneous surface (see Fig. 37-20, step 3). Use a scalpel or a hemostat to puncture the abscess cavity (see Fig. 37-20, step 4). It can be difficult to enter this deep abscess cavity. Failure to obtain frank pus or to appreciate a “pop” when entering the abscess usually prognosticates failure of the procedure. Stabilize the abscess with the thumb and forefinger, hold the hemostat in place, and skewer the abscess onto the hemostat (Fig. 37-21). Pushing the hemostat into the immobilized abscess is technically more difficult. Make a stab incision large enough to accommodate the catheter but small enough to prohibit the inflated balloon from being extruded. Once the abscess has been entered (signaled by a palpable pop or the free flow of pus), place the deflated balloon in the abscess cavity (see Fig. 37-20, step 5). Inflate the balloon with 2 to 4 mL of water (not air). Persistent pain indicates that too much fluid has been used. Most abscesses drain for a few days, and the Word catheter often falls out within a week. Ideally, the device is left in place for 2 to 4 weeks to allow fistula formation, so follow-up is required. If the catheter falls out prematurely, it should be replaced quickly to allow fistulization. Some clinicians do not reinsert the catheter if healing has progressed significantly after the first drainage procedure.

Alternative treatment strategies have also been explored. Gennis and coworkers¹²⁰ designed a rubber ring catheter called the Jacobi ring from an 8-Fr T-tube threaded with 2-0 silk suture material (Fig. 37-22). The catheter enters and exits the abscess through separate incisions, and a closed ring is formed when the ends of the suture are tied (Fig. 37-23). The device was tested in a randomized study involving 38 women, 25 of whom received a ring catheter and 13 received a Word catheter. The catheters were rated similarly in terms of successful placement, abscess resolution (all resolved within 3 weeks), and recurrence rates (no recurrences at 6 months and two [one in each treatment group] at 1 year). However, the ring catheter outperformed the Word catheter in patient satisfaction.

A loop device similar to the Jacobi ring can be created from butterfly Vacutainer tubing and 2-0 suture. The availability of such equipment in most institutions makes this an attractive option. Jacobi rings or similar loop devices have the advantage of a lower risk for dislodgment than with the Word catheter. Disadvantages include the creation of two drainage tracts in comparison to one. Additionally, loop devices require pelvic rest, whereas the patient may resume intercourse with the Word cathether.¹²¹

Standard I&D can give the patient immediate relief, but this procedure is not recommended because the abscess recurrence rate is so high.¹²² However, if neither a Word catheter nor equipment for a loop device are available, I&D can be performed, with the caveat that the clinician and the patient must appreciate the likelihood of an unfavorable long-term outcome. Make the incision over the medial surface of the introitus (on the mucosa, not on the skin) in a line parallel to the posterior margin of the hymenal ring. The abscess cavity is slightly deeper than most cutaneous abscesses, so the clinician must be certain to enter the actual abscess cavity to achieve complete drainage. This is most easily accomplished by inserting a hemostat through the mucosal incision and spreading the tips of the instrument in the deeper soft tissue. After the contents have drained, pack the abscess for 24 to 48 hours, and start sitz baths thereafter.

CO₂ laser vaporization is another technique described whereby laser technology is used to create an opening in the area of the duct’s orifice. The abscess is then evacuated and either excised, vaporized, or left intact.¹²³ Lack of available equipment, however, precludes using this method in the ED. Silver nitrate sticks have also been used to ablate the cyst after I&D. Complications of this method include postoperative vulvar burning, labial edema, and cauterization of the surrounding mucosa.¹²⁴

Empirical antibiotics are indicated only for patients with a frank abscess and local cellulitis. More than 80% of cultures from Bartholin’s cysts show no growth, and the same is true for a third of cultures from abscesses.¹²⁵ Cultures that are positive typically show polymicrobial growth, usually anaerobes and especially Bacteroides species and other colonic bacteria. Much less often, N. gonorrhoeae or Chlamydia trachomatis is cultured from the abscess cavity. Chronic low-grade inflammation from a gonococcal infection has been implicated as a causative factor in cyst formation and occasionally in the development of an abscess; therefore, choose an antibiotic that will provide coverage for N. gonorrhoeae. It is reasonable to culture cervical and anal specimens for gonorrhea and chlamydia from women with a Bartholin gland abscess because of the association of these infections with sexually transmitted disease.¹²⁶ However, empirical treatment of gonorrhea or chlamydia is not necessary unless the clinician has a high suspicion that a sexually transmitted organism is the infectious cause. At the current time, CA-MRSA infections of the Bartholin glands are uncommon.

Particular care must be taken when treating a pregnant woman with a Bartholin gland abscess because she is at high risk for complications. Sepsis in a pregnant woman following marsupialization of an abscess has been reported.¹²⁷ Postmenopausal women with what appears to be a Bartholin gland abscess should be referred to a gynecologist to rule out malignancy. A vulvar abscess in an HIV-positive woman should raise suspicion for Kaposi’s sarcoma.¹²⁸

Recurrence is a complication with all the aforementioned techniques. If the abscess recurs, more definitive therapy in the form of marsupialization or complete excision of the gland may be required; however, these procedures are not performed initially and, when chosen, should be done in an OR.

Pilonidal Abscess

Pilonidal sinuses are common malformations that occur in the sacrococcygeal area (Fig. 37-24). The cause of the sinus formation is unclear, and the malformation may occur during embryogenesis. Pilonidal cyst formation is thought to be secondary to blockage of a pilonidal sinus. The result of this obstruction is repeated soft tissue infection, followed by drainage and partial resolution, with eventual reaccumulation. The blockage is most commonly the result of hair in the region, and the lesion may in part be a foreign body (hair) granuloma. Although pilonidal sinuses are present from birth, they are not usually manifested clinically until adolescence or the early adult years. Pilonidal abscess formation most frequently affects young (often white) adult males. The sinuses and cysts are lined with stratified squamous epithelium and, after excision, may be found to contain wads of hair and debris. When cultured, pilonidal abscesses generally yield mixed fecal flora with a preponderance of anaerobes.¹²⁹ Poor hygiene and repeated trauma (called “jeep bottom” in World War II) may precipitate acute infection. It is postulated that as a patient sits, microtrauma in the intergluteal cleft acts as a suction that draws hair into the superior gluteal folds. Subsequently, hairs become ingrown, bacteria invade, and an abscess developsin the sacrococcygeal region. At the current time, CA-MRSA infections are not common.

Patients with a pilonidal abscess will seek care for back pain and local tenderness. On physical examination the area is found to be indurated. Frank abscess formation may not be appreciated in this deep abscess. One will usually see barely perceptible dimples or tiny openings at the rostral end of the gluteal crease (Fig. 37-25). A hair or 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 draining chronically, or they may become infected as the size increases and blockage occurs.¹³⁰

Treatment of an 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 (see Figs. 37-6 and 37-13). The abscess cavity may be quite large and thus necessitate a lengthy incision to ensure complete drainage. There is some evidence to support lateral, off-midline incisions. A retrospective study looked at 48 patients who had undergone lateral incisions and matched them with 48 patients who had undergone midline incisions. Those who had undergone midline incisions took approximately 3 weeks longer to heal than did those drained with a lateral incision.¹³¹ In general, reported median healing times after I&D vary between 12 and 63 days.^132,133 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. Antibiotic therapy is not generally required.

Simple I&D is not usually curative, with recurrence rates of 5% to 13% reported134,135; therefore, the patient should be referred to a surgeon for removal of the cyst and sinus after the inflammatory process has resolved. 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 achieve complete drainage. The extent of the cyst cavity and the volume of pus encountered on initial incision can be surprising.

Closure strategies for these potentially large wounds vary. Gencosmanoglu and Inceoglu¹³³ concluded that a modified lay-open technique is superior to excision with primary closure for chronic pilonidal sinuses with regard to morbidity and recurrence rates. Other closure options after extensive resection of complex or recurrent sinus tracts are Z-plasty, an advancement flap, or a rotational flap. When primary closure is chosen, administration of a broad-spectrum regimen of antibiotics (e.g., preoperative infusion of cefuroxime and metronidazole followed by 5 days of oral co-amoxiclav¹³⁶) offers protection against wound infections.

Perirectal Abscesses

Most anorectal infections originate in the cryptoglandular area located in the anal canal at the level of the dentate line. Abscesses within these glands can penetrate the surrounding sphincter and track in a variety of directions, with larger abscesses occurring within the perianal, intersphincteric, ischiorectal, and supralevator spaces. A small number of anorectal abscesses have a noncryptoglandular cause such as Crohn’s disease, atypical infection (e.g., tuberculosis, lymphogranuloma venereum), malignancy, or trauma.¹³⁷

Perirectal infections can range from minor irritation to fatal illness. Surprisingly, clandestine infections often occur in diabetics. Successful management depends on early recognition of the disease process and adequate surgical therapy. Small abscesses can initially be managed on an outpatient basis with simple I&D, described previously. Because of the morbidity and mortality associated with inadequate treatment of these conditions, patients with large and deep abscesses should be promptly admitted to the hospital for evaluation and treatment under general or spinal anesthesia (Fig. 37-26).

It is important to understand the anatomy of the anal canal and the rectum to appreciate the pathophysiology of these abscesses and their treatment (Fig. 37-27). 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 that 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 the 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. 37-28).^136,138

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 are connected by fibrous tissue to the external sphincter system, which consists of three circular muscle groups.

Infected Sebaceous Cyst

A common entity that appears as a cutaneous abscess is an infected sebaceous cyst. Such infections are increasingly being caused by CA-MRSA. Sebaceous cysts, caused by obstruction of sebaceous gland ducts, can occur anywhere on the body. The cyst becomes filled with a thick, cheesy, sebaceous material, and the contents frequently become infected. Sebaceous cysts can be quite large and may persist for many years before they become infected. When infected, they appear clinically as tender, fluctuant subcutaneous masses, often with overlying erythema.

The initial treatment of an infected sebaceous cyst is simple I&D (Fig. 37-29). The loop drainage technique may not be suited for this abscess. The thick sebaceous material must be expressed because it is too thick to drain spontaneously. 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. 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 at a later visit, when it can be more easily identified. Alternatively, the entire cyst can be removed during the 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. After 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 colleagues¹⁴⁷ reported a randomized study of 71 patients treated by either traditional I&D or primary resection of the cyst, followed by irrigation and wound closure. In this study the patients treated by primary resection had faster healing, fewer days of pain, and less scarring.

Paronychia

Paronychia is an infection localized to the area around the nail root (Fig. 37-30). It is a common infection probably caused by frequent trauma to the delicate skin around the fingernail and the cuticle. These type of infections have also been linked to “insults” induced by nail cosmetics (mechanical trauma, irritant reactions, and allergic reactions)¹⁴⁸ and to a number of occupations (e.g., hair cutting and meat handling).¹⁴⁹ 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 and form a subungual abscess. Lymphadenitis and lymphadenopathy are not usually 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.¹⁵⁰ Paronychia in children is often caused by anaerobes, and it is believed that this is the result of finger sucking and nail biting. Occasionally, a group A β-hemolytic streptococcal infection will develop in a paronychia in a child with streptococcal pharyngitis who engages in thumb sucking.^151,152 Paronychias involving CA-MRSA have been reported.^153,154

A paronychia appears as a swelling and tenderness of the soft tissue along the base or the side of a fingernail (Fig. 37-31). 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 nail bed is mobile, the infectious process has extended under the nail, and a more extensive drainage procedure should be performed. Although no comparative trials of surgical management versus oral antibiotics have been performed,¹⁵⁵ some general guidelines for the management of paronychias have become established in clinical practice. If soft tissue swelling is present without fluctuance, remission may be achieved with frequent hot soaks (six to eight times a day) and a short course of oral antibiotics (3 to 4 days).¹⁵⁶ Incision will be of little value at this early cellulitic phase. Antibiotic treatment of localized infection is summarized in Table 37-2. If significant cellulitis is present, a broad-spectrum antistaphylococcal antibiotic (cephalosporin or semisynthetic penicillin) may be tried. Splint and elevate the digit.^156,157

When a definite abscess has formed, drainage is usually curative quickly. A number of invasive operative approaches have been suggested. 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 eponychial fold away from the nail matrix 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 the proximal end of the fingernail. Drainage may be accomplished without anesthesia in selected patients,¹⁵⁸ but a digital nerve block is frequently required. After softening the eponychium by soaking, advance a No. 11 scalpel blade, scissors, or a 21- to 23-gauge needle parallel to the nail and under the eponychium at the site of maximal swelling (Fig. 37-32).^157,159,160 Pus escapes rapidly, with immediate relief of pain. A tourniquet placed at the base of the finger may limit bleeding and aid the clinician in determining the exact extent of the infection during the drainage procedure.

If more than a tiny pocket of pus is present, fan the knife tip or needle or spread the scissors under the eponychium while keeping the instrument parallel to the plane of the fingernail (see Fig. 37-32, steps 5 and 6). When a large amount of pus is drained, slip a small piece of packing gauze 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 the surrounding area of cellulitis is minimal. An alternative to systemic antibiotics is to keep the operative site bathed in antibiotic ointment. After the anesthesia has worn off, start the patient on frequent soaks in warm tap water at home. In most cases the patient may easily remove the packing. At 24 to 36 hours, soak the finger in hot water and pull the gauze out; a repeated visit to a clinician is not required if healing is progressing, but follow-up examinations should always be encouraged. Once the packing is removed, cover the area with a dry, absorbent dressing. Apply an antibiotic ointment to the site for a few days. The benefit of antibiotic ointments in reducing infection is unproven, but instruct the patient on detailed use of the ointment. The ointment helps keep the bandage from sticking.

An alternative technique called the Swiss roll technique was described by Pabari and colleagues for severe acute paronychia with a run-around or contiguous infection of both nail folds. With a No. 15 scalpel blade pointing away from the nail bed, make an incision on both sides of the nail fold. The nail fold, after thorough irrigation with saline, is then rolled proximally over nonadherent dressing, like a swiss roll, and sutured to the skin with a nonabsorbable dressing. Apply a finger dressing. Remove the sutures in 48 hours and unfold the nail fold back to its original position to allow it to heal by secondary intention.¹⁶¹ The authors argue that this technique spares the nail plate and allows rapid healing, although no controlled studies have compared this technique with simple incision followed by packing gauze described above.

If the infection has produced purulence beneath the nail (subungual abscess), remove a portion of the nail or trephinate the nail to ensure complete drainage. As an alternative to nail removal, place a hole in the proximal part of the nail with a hot paper clip or a portable electrocautery device. Make a large opening or multiple holes to ensure continued drainage. The proximal portion of the nail is involved in most cases. Treat this by bluntly elevating the eponychium to expose the proximal edge of the nail. Elevate the proximal third of the nail from the nail bed and resect it with scissors. Leave the distal two thirds of the nail in place to act as a physiologic dressing and to decrease postoperative pain (Fig. 37-33). If purulence is found below the lateral edge of the nail, gently elevate the affected part and excise it longitudinally.¹⁶² Exercise care during this procedure to avoid damage to the nail matrix. Place a wick of gauze beneath the eponychium for 48 hours to ensure continued drainage.

Most paronychias resolve in a few days, and one to two 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. Clinical infection lasting longer than a few weeks should prompt evaluation for osteomyelitis of the distal phalanx, a well-known but rare complication of even a properly drained paronychia.

Patients occasionally come to the ED complaining of a chronic, indolent paronychial infection. These seldom respond to ED intervention. Frank purulence is rarely present, and conservative treatments are often unsatisfactory. Many causes of this frustrating condition have been described, including fungal, bacterial, viral, and psoriatic conditions. Screen patients for malignancy if they have chronic paronychia that is unresponsive to therapy.¹⁵⁹ 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.¹⁶⁰ Refer these patients to a dermatologist or hand surgeon because of the prolonged treatment required.

Herpetic Whitlow

Herpetic whitlow is an extremely contagious infection of the distal phalanx caused by herpes simplex virus (type 1 or 2) (Fig. 37-34). In children, herpetic whitlow tends to be associated with gingivostomatosis caused by herpes simplex 1, whereas adults most commonly harbor herpes simplex 2. Inoculation occurs through a discontinuity in the skin.¹⁶³ Health care providers exposed to oral secretions (e.g., dental hygienists and respiratory therapists) and patients with other herpes infections are most commonly infected.^164,165 After a 2-day to 2-week incubation period, an infected individual may experience prodromal signs and symptoms such as fever, malaise, lymphadenitis, and axillary lymphadenopathy. In the affected finger the infection is characterized by tenderness followed by throbbing pain (out of proportion to the findings on physical examination), edema, and erythema. Vesicles containing clear, bloody, or cloudy fluid form and mark the most infectious stage of the process. Viral vesicles typically involve the digits but can also involve other areas of the hand.¹⁶⁶ The lesions are usually quite painful but are self-limited and resolve in 2 to 3 weeks. I&D of herpetic whitlow is contraindicated because it may induce a secondary bacterial infection and delay healing.^164,167 Treatment is symptomatic and consists of splinting, elevation, and analgesia as needed. Oral antiviral agents effective against herpes infections (acyclovir, famciclovir, or valacyclovir) can shorten the course of the disease if given early (see Box 37-3). After an accidental needlestick in health care workers, oral famciclovir may be used as a preventive.¹⁶⁸ Infection recurs in 30% to 50% of cases, but the initial infection is usually the most severe. Acyclovir, 200 mg taken orally three to four times a day, can decrease recurrence rates.¹⁶⁵

Consideration must be given to preventing spread of the infection. An occlusive dressing decreases the chance of viral transmission, but health care providers with herpetic whitlow should limit and perhaps even refrain from patient contact, especially until all lesions have crusted over and viral shedding has stopped.169,170 Compliance with universal precautions will decrease the likelihood of patient-to-provider transmission.

Felon

A felon is an infection of the pulp of the distal end of the finger (Fig. 37-35). 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 many fibrous septa extend from the volar skin of the fat pad to the periosteum of the phalanx; these septa subdivide and compartmentalize the pulp area. When an infection occurs in the pulp, these 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 and initiate an ischemic process that compounds the infection. The infection can progress to osteomyelitis of the distal phalanx, septic arthritis, and flexor tenosynovitis. Although the septa may facilitate an infection in the pulp, they also provide a barrier that protects the joint space and tendon sheath by limiting proximal spread of the infection.

In most cases the offending organism is S. aureus, but mixed infections and gram-negative infection may also occur. A study looking at the bacteriology of hand infections over an 11-year period found that of 159 hand infections, 48 (30%) harbored CA-MRSA, the incidence of CA-MRSA increased by 41% per year, and IV drug use and felon infections in particular were risk factors for CA-MRSA.¹⁶² These changing patterns, along with the often protracted course of felons and concern for osteomyelitis, make this one of the few soft tissue infections in which culture may be helpful.

A patient in whom a felon is developing will describe a gradual onset of pain and tenderness of the fingertip. In a few days the pain becomes 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 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 the pain is so intense in the dependent position. Cessation of pain indicates necrosis and nerve degeneration.

During the early stages of cellulitis, a felon may be controlled by treatment consisting of elevation, oral antibiotics (see Box 37-3), and warm water or saline soaks. For more developed felons, proper treatment consists of early and complete I&D.¹⁶⁴ Antibiotics alone are not curative once suppuration has occurred. Delaying surgery may result in permanent disability and deformity.

A minor felon can usually be drained on an outpatient basis with a digital nerve block (Fig. 37-36). A long-acting anesthetic (bupivacaine) will prolong the anesthesia. A tourniquet (1.25-cm Penrose drain) can be used to allow an incision into a bloodless field. Surgical drainage must be performed carefully to avoid injury to nerves, vessels, and flexor tendons. Most felons can be managed with a limited procedure, but many surgical options have been advocated, none of which has been proved to be superior for all circumstances.¹⁶⁴ Traditional incisions (“hockey stick” or “fish mouth”) have a propensity for complications such as sloughing of tissue and postoperative fat pad anesthesia or instability and are rarely used. The preferred initial treatment is a simple longitudinal incision over the area of greatest fluctuance,^171,172 3 to 5 mm distal to the distal interphalangeal joint. The incision may be made laterally or along the volar surface (see Fig. 37-36A), although injury to the sensory nerve or digital artery is more of a concern with the lateral incision given its proximity to these structures. 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 foreign body should be sought even if the history is not known. 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. The subcutaneous tissue is bluntly dissected with 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 by a hand specialist. Follow-up recommendations for patients with a diagnosis of felon should include referral to a hand surgeon.

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. A snug dressing, splinting, elevation, and adequate opioid analgesics are prerequisites for a successful outcome. Most felons are treated empirically with antibiotics for at least 5 days. A broad-spectrum cephalosporin is a reasonable choice pending cultures (if done). Antibiotics effective against CA-MRSA should also be considered given its increasing incidence. MRSA infections can be treated with vancomycin, 1 g twice a day, or linezolid and may require weeks until resolution.¹⁷³ Oral linezolid may allow outpatient treatment.

The patient should be rechecked in 2 to 3 days. On the first postoperative visit, perform a digital block and remove the packing if present. Irrigate the incision copiously with saline, and remove any additional necrotic tissue. If there is continued drainage at this time, replace the drain for 24 to 48 hours, but it can usually be removed and a dressing reapplied. Soaking may be advised. At the first revisit, check the sensitivities of the bacterial cultures, and make a decision to continue or change antibiotics.

Some clinicians advocate radiographic evaluation for retained foreign bodies at the initial visit, as well as a baseline evaluation of the bone for subsequent evaluation of osteomyelitis. Other clinicians 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. Persistent infections necessitate more radical I&D and may require IV antibiotics. After adequate drainage, osteomyelitis may respond surprisingly well to outpatient antibiotic therapy, with almost complete regeneration of bone being achieved if the I&D procedure has been adequate.

Fingertip infections can be stubborn. 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

Subungual hematomas are typically caused by hitting a fingertip with a hammer, slamming a finger in a door (Fig. 37-37), or dropping a weight on a foot. The patient’s main concern is obtaining relief from the terrible throbbing pain that increases with the pressure under the nail.

When describing the injury, the clinician should estimate the percentage of nail bed that is affected by the hematoma and discuss associated trauma to the nail margins or surrounding tissue. The examination should include tests of the extensor and flexor tendons, of circulation by capillary refill, and of the sensitivity of the area.¹⁷⁴

If fracture of the distal phalanx is suspected (e.g., if the fingertip is unstable or the mechanism of injury suggests a fracture), obtain anteroposterior and lateral x-ray films. Radiographs differentiate tendinous from bony mallet-type injuries. Crush injuries are associated with three types of distal phalanx fractures: longitudinal, transverse, and comminuted. If the fracture is angulated, displaced, unstable, or intraarticular or involves a third or more of the articular surface, refer the patient to a hand surgeon.¹⁷⁵ Because trephination in patients with a distal phalanx fracture converts a closed fracture into an open one, there is concern about infectious and cosmetic complications. In the two studies that examined this possible association,^176,177 with fracture subsets totaling 26, no infections occurred. The presence of an underlying fracture does not contraindicate nail trephination for fear of converting a closed fracture into an open one.

Nail removal is unnecessary, even if there is an underlying distal phalanx fracture, as long as the nail margins and nail are intact.178,179 If the nail is split, avulsed or disrupted or a nail bed laceration extends to the skin, the nail should be removed and the underlying nail bed repaired (see further discussion in Chapter 35). Simple trephination of an uncomplicated subungual hematoma, even if it involves the entire subungual area, results in a good outcome functionally and cosmetically.¹⁸⁰ Trephination should also be considered if the hematoma covers more than half the intact nail or if it is smaller but painful.

Prophylactic antibiotics are not necessary for patients with uncomplicated subungual hematomas that have been trephinated. For more serious injuries, a slight risk for infection exists, but in most cases, rigorous wound cleaning and careful soft tissue repair constitute adequate treatment.181,182

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