Clinical Features

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Patients present with an area of swelling, tenderness, and erythema. Inspection of the area may reveal fluctuance, induration, or active drainage. Lymphadenitis, localized lymphadenopathy, or fever may indicate systemic involvement of the infection, but in otherwise healthy patients, cutaneous abscesses tend to remain localized. A careful history should be obtained, with special attention given to underlying immunocompromising illnesses, steroid or other immunosuppressive drug use, and alcoholism. Close inspection of the area for evidence of predisposing injury or foreign body is important. Radiography may be indicated to evaluate for certain radiopaque foreign bodies, and ultrasound may be useful in identifying nonradiopaque objects. Ultrasound can accurately identify many small foreign objects or at least a small fluid collection representing surrounding abscess. The limiting factor in the use of ultrasound is that because of the superficial location of most of these objects, a very high frequency ultrasound transducer is required (7.5-10 MHz). Specific abscesses that may be encountered in the ED are discussed below.

BARTHOLIN GLAND ABSCESSES Bartholin gland abcesses are seen primarily in sexually active women. Another diagnosis should be considered in postmenopausal women. The Bartholin or vestibular glands are located at the 5 and 7 o'clock positions of the vaginal vestibule. The glands are secretory in nature, and obstruction of the ducts can cause retention of secretions leading to cyst and eventually abscess formation. The patient presents with a unilateral painful swelling of the labia and with a fluctuant 1- to 2-cm. mass at the location of Bartholin's gland. Neisseria gonorrhoea and Chlamydia trachomatis are often isolated in these abscesses, and cervical cultures are recommended in all patients with Bartholin's gland abscesses. Treatment is not recommended routinely, except in patients with a high clinical suspicion for sexually transmitted disease. Anaerobes, especially Bacteroides species, are also common, as are the gram-negative organisms typically colonizing the perineal region. Treatment involves incision and drainage along the vaginal mucosal surface. There is a very high incidence of reinfection if more definitive steps are not taken to form a permanent fistulous tract. This can be done by using a Word catheter, a small catheter with a balloon on the distal end used to hold the abscess cavity open during healing, or by marsupializing the abscess walls.

PARONYCHIA AND FELONS Paronychia and felons are discussed in Chap 277, "Hand Infections."

HIDRADENITIS SUPPURATIVA Hidradenitis suppurativa is a recurrent, chronic infection involving the apocrine sweat glands. Blockage of these glands by keratinous material leads to inflammation, local cellulitis, and subsequent abscess formation. Multiple areas of infection develop in different apocrine glands and coalesce to form chronic draining fistulous tracts. These tracts tend to occur in the axilla and groin, where the apocrine sweat glands predominate. Hidradenitis suppurative is more common in women and blacks, and there appears to be a genetic factor involved in its development. Obesity, shaving, and poor hygiene also contribute. The causative organism is usually Staphylococcus, but Streptococcus also can be involved. In the groin, gram-negative organisms and anaerobes also may be seen. Patients often will present with multiple lesions in different stages of development and healing but with an acute exacerbation in one or a few areas. ED treatment is directed primarily at incision and drainage of the acute infection with referral to a surgeon for further definitive treatment. This often requires wide excision of the affected area. Oral antibiotics should be used in patients with significant areas of cellulitis.

INFECTED SEBACEOUS CYSTS Sebaceous glands occur diffusely throughout the body. Blockage of the duct of a sebaceous gland may lead to development of a glandular cyst that may exist for a long period of time without becoming infected. Once bacterial invasion occurs, abscess formation is common. These patients typically present with an erythematous, tender cutaneous nodule that is commonly fluctuant. Simple incision and drainage are the appropriate ED treatment. The cyst always contains a capsule that must be removed to prevent further infection. This is usually best done at a later follow-up visit when the initial inflamation has improved or resolved. Occasionally, the wall of the sac can be grasped with a forceps and removed at the time of drainage.

PERIRECTAL ABSCESSES Most, if not all, perirectal infections are felt to arise from mucinous glands located within the anal crypts. Blockage of the ducts to these glands leads to bacterial invasion, infection, and commonly, abscess formation. The location of the subsequent abscess depends on the direction in which the infection spreads. The most common area of infection is the perianal abscess that is located superficially below the anal ring. Ischiorectal abscesses, supralevator abscesses, and intersphincteric abscesses all are caused by spread of infection into deeper perirectal tissues. Perirectal abscesses are more common in middle-aged males with other risk factors, including inflamatory bowel disease, diabetes, and other immunocompromising illnesses. The bacterial etiology of these infections is primarily the normal fecal flora. Mixed anaerobic and aerobic infections predominate, with B. fragilis being the primary anaerobe. Perirectal abscesses can represent serious, life-threatening infections, and only the most superficial should be treated with local anesthesia and incision and drainage in the ED.

PILONIDAL ABSCESSES Pilonidal abscesses are located along the superior gluteal fold. It is thought that a pilonidal sinus forms along the gluteal fold possibly at the time of embryogenesis, although others believe it to be secondary to local soft tissue trauma. These sinuses are lined with squamous epithelium and hair. It is blockage of the sinus tract with hair and other keratinous material that leads to bacterial invasion and infection. The causative organisms typically are normal skin flora, with Staphylococcus species being the most common. Contamination with peritoneal and fecal organisms is also possible. Patients tend to develop symptoms in their late teens and early twenties, and without definitive surgical treatment, they tend to have recurrent infections, sometimes developing a chronic draining fistulous tract. Patients typically present to the ED with a tender, swollen, and fluctuant nodule located along the superior gluteal fold. Systemic symptoms are rare. The appropriate initial treatment includes incision and drainage using care to remove all excess hair and debris from the abscess cavity. The cavity should be packed with iodoform gauze, and the patient should return in 2 to 3 days for advancement of the packing. Antibiotics generally are not needed. Surgical referral is recommended for more definitive treatment.

STAPHYLOCOCCAL SOFT TISSUE ABSCESSES Staphylococcus species are ubiquitous throughout the skin and have a particular affinity for hair follicles, where infection is common. Inflammation of a hair follicle caused by bacterial invasion is known as folliculitis and is best treated noninvasively with warm soaks. A deeper invasion into the soft tissue surrounding a hair follicle can lead to a localized abscess formation called a furuncle (boil). These are most commonly found on the face, neck, back, axilla, and inner thigh. Unless severe, warm compresses usually are adequate to promote spontaneous drainage. In the thick skin on the back of the neck, several furuncles may coalesce to form a large area of infection containing many interconnected sinus tracts and abscesses. This is known as a carbuncle and often requires surgical wide excision for complete resolution. Carbuncles are seen much more commonly in diabetics and may demonstrate signs of systemic involvement.

Diagnosis Most simple cutaneous abscesses in otherwise healthy patients are local infections without need for further evaluation. Clinical presentation of a tender, swollen, often erythematous nodule strongly suggests infection. A palpable area of fluctuance is typically enough for the diagnosis of abscess. Notice should be made of the admitting vital signs, with particular attention to temperature and heart rate. Fever or tachycardia suggests systemic involvement of the infection and may indicate the need for further laboratory testing. In patients with diabetes, alcoholism, and other immunocompromising conditions, the threshold for further diagnostic studies should be lower. A complete blood count and in certain situations (such as possible osteomyelitis) an erythrocyte sedimentation rate usually are all that are needed to evaluate for possible systemic involvement. Diabetic patients routinely should have blood glucose checked.

In simple abscesses involving otherwise healthy patients, a routine culture and sensitivity is not needed. If it is felt that antibiotic treatment is indicated, the causative organisms usually can be predicted by the general location of the abscess. If further certainty is required, a Gram stain of the abscess aspirate most often will lend the required information, and results can be obtained while the patient is still in the ED. Gram-positive cocci in clusters suggest infection with S. aureus, whereas many different organisms suggest a mixed anaerobic and aerobic infection. In patients in whom possible deep or chronic infection may complicate the course, early wound cultures with sensitivities may prove useful. Immunocompromised patients demonstrating systemic signs of infection also should have blood cultures drawn. In patients in whom foreign body involvement is a potential issue, plain radiographs or possibly ultrasound should be used to assist in identification.

Treatment Incision and drainage are the only treatment necessary in most cases of superficial and localized abscesses. Often it is difficult to determine clinically if an area of fluctuance is present within an area of induration and swelling. Needle aspiration of the most likely area of induration often can help in the diagnosis. When pus is encountered with aspiration, incision and drainage should be performed. When no pus is located, a trial of antibiotic therapy and warm compresses is appropriate initially. These patients should have a follow-up evaluation scheduled because many will need incision and drainage in the future.

Consideration must be given to the best location for abscess drainage. Abscesses well suited to ED treatment are those which are superficial, well localized, and not in close proximity to nerves or vascular structures. Fluctuant masses should be examined for pulsations or bruits if near vascular structures. Patient comfort is also an important consideration. Infiltration of a local anesthetic most often gives poor pain relief. The lower pH of infected tissue typically greatly reduces the effectiveness of a local anesthetic. Injecting additional fluid into an already swollen and tender area also increases pain. Regional or field blocks can be used effectively at times, and digital blocks to assist in the drainage of a large paronychia or felon are usually all that are needed. Patients with evidence of deeper tissue infection, as in many cases of perirectal abscess, and those in whom adequate analgesia cannot be obtained in the ED should be taken to the operating room for appropriate surgical drainage.

Nitrous oxide has been used with good success in many EDs for years. The parenteral use of rapid and ultra-short-acting sedatives and analgesics for conscious sedation in the ED has been shown to be both safe and effective when they are used appropriately. They are best suited for procedures that are very painful and short in duration. Incision and drainage seem ideal in this regard. Many agents have been used effectively, with the combination of fentanyl and midazolam being one of the more common and effective. Both these agents have a short time to peak effect (3-5 min for midazolam and <1 min for fentanyl) and a short duration of action 1

(each 1 to 1 2 h), which allows the patient to be discharged at his or her presedation mental status baseline without a prolonged recovery period. Furthermore, the patient benefits from the analgesic effect of the fentanyl as well as the sedative, anxiolytic, and amnestic effects of the midazolam. Fentanyl, with less than 1 min to peak effect, is very well suited to titration for desired effect during the procedure. For further discussion, see Chap 33.

Prior to any sedation or analgesia, the procedure should be explained to the patient, including any possible complications. With most superficial abscesses, the risks involved are relatively few. The possibility of severing a cutaneous nerve with residual local numbness, as well as the risk of injury to deeper nerves and blood vessels, should be discussed. The possibility of poor or delayed wound healing should be discussed in patients with diabetes or peripheral vascular disease. Some estimate should be made of the residual scarring that may be anticipated, especially in areas of cosmetic significance. As with all elective and invasive procedures, informed consent should be obtained in all patients. Although the risk of complications is low, informed consent prior to the procedure ensures that the patient has been appropriately educated concerning the risks and benefits, as well as optimizing medicolegal coverage for the clinician. Informed consent in patients receiving conscious sedation is also important and should cover the risk of respiratory depression requiring endotracheal intubation.

The patient should be positioned to ensure appropriate access to the abscess and in the most comfortable position possible. The area should be prepared with Betadine and draped in a sterile fashion. After appropriate anesthesia, the abscess should be opened widely over the area of greatest fluctuance, using a No. 11 or 15 scalpel blade to ensure adequate drainage. As much pus as possible should be expressed by gentle compression. Hemostats are then used to break up any loculated areas within the abscess cavity. The cavity is irrigated with saline and packed loosely with gauze tape to hold it open to promote drainage while the infection resolves. The packing should be left in place long enough for the cavity to heal from the inside out, preventing recollection of the abscess. Patients are discharged with instructions for warm compresses or soaks three to four times a day. A follow-up visit should be scheduled in 2 to 3 days for recheck and advancement or replacement of the packing. Wounds that continue to actively drain at the time of follow-up should have the packing replaced. Replacing the packing performs some degree of debridement of the abscess cavity, as well as providing fresh packing for absorption of pus and debris. Wounds that are not actively draining can have the packing advanced as needed to allow for internal healing while keeping the incision open to promote drainage.

The use of antibiotics in patients with cutaneous abscesses is somewhat controversial. The risk of systemic infection following local incision and drainage appears to be low. A recent ED study demonstrated that in 50 afebrile patients in whom blood cultures were drawn 2 and 10 min after incision and drainage of cutaneous abscesses, none of the cultures was found to be positive.9 There are no good data suggesting that antibiotic treatment following incision and drainage speeds infection resolution in otherwise healthy patients. Generally, it is felt that in patients without underlying immunocompromising conditions or signs of systemic infection, antibiotics are not indicated following incision and drainage of superficial cutaneous abscesses. With a lack of hard scientific data pointing to clear-cut guidelines for antibiotic therapy, clinical judgment needs to be exercised. In patients with diabetes, alcoholism, or other underlying immunocompromising illnesses, or in those on immunosuppressant medications such as steroids or chemotherapeutics, the threshold for antibiotic use should be much lower. Furthermore, patients who present with signs of systemic disease such as fever and chills and those with cellulitis extending beyond the abscess borders also should be considered for antibiotic therapy. Abscesses involving the hands or face should be treated more aggressively with antibiotics because of the higher morbidity associated with prolonged infection or complications. The specific antibiotic used should be chosen according to the most likely pathogen involved. This can be somewhat predicted by the location of the infection. Duration of therapy should be directed to some degree by the severity of infection but typically should continue for 5 to 7 days.

Of separate concern are patients with underlying structural heart disease at risk for bacterial endocarditis. Certain structural cardiac conditions lead to a higher incidence of bacterial endocarditis. Futhermore, the severity of disease and morbidity are increased in patients with certain underlying cardiac diseases who develop bacterial endocarditis. The American Heart Association recently has updated its guidelines for patients at increased risk for developing bacterial endocarditis. 10 Table 1.4.6.-1. outlines the cardiac conditions considered to be at high and moderate risk based on predicted outcomes if endocarditis does occur. Note that several types of patients frequently encountered in the ED, namely, patients after coronary artery bypass grafting, those with pacemakers, and those with mitral valve prolapse without valvular regurgitation, are not recommended for endocarditis prophylaxis. Despite the apparent low risk of transient bacteremia following incision and drainage of a simple cutaneous abscess, the American Heart Association recommends prophylactic antibiotics for those patients in the high- and moderate-risk catagories prior to the procedure. No mention is made of postprocedure treatment. The antibiotic selected should be directed at the most likely organism causing the abscess. Table

14.6-2. outlines suggested antibiotic treatment by organism for soft tissue infections and should be used for preprocedure prophylaxis for endocarditis. An intravenous or intramuscular antistaphylococcal penicillin, clindamycin, or first-generation cephalosporin is appropriate for patients not able to take oral medications. In patients with known methicillin-resistant S. aureus infection, vancomycin is recommended for prophylaxis.

TABLE 146-1 Cardiac Conditions at Risk for Endocarditis

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