A 48-year-old man with a history of alcoholism and cirrhosis undergoes evaluation for severe left leg pain and fever. The patient says his symptoms began after he scraped the lateral aspect of his knee at home 3 days ago. During the past 2 days he has had subjective fevers and noticed decreased urinary frequency. The patient has been self-medicating with aspirin for these symptoms. He consumes approximately 16 oz of whiskey per day and smokes one pack of cigarettes per day. On physical examination, his temperature is 39.2°C (102.6°F), pulse rate 110 beats/min, blood pressure 115/78 mm Hg, and respiratory rate 28 breaths/min. His skin is mildly icteric. The findings from his cardiopulmonary examination are unremarkable. The abdomen is soft and without hepatosplenomegaly or ascites. The left leg is edematous from the ankle to the upper thigh. The skin is tense and exquisitely tender; however, it is without erythema, fluctuance, necrosis, or vesicular changes. Examination of the other leg reveals normal findings. Laboratory studies demonstrate a WBC count of 26,000/mm3 and normal hemoglobin and hematocrit values. Other laboratory studies reveal sodium 128 mEq/L, glucose 180 mg/dL, total bilirubin 3.8 mg/dL, and direct bilirubin 1.5 mg/dL. Radiographs of the left leg reveal no bony injuries and no evidence of air in the subcutaneous soft tissue space.
What is the most likely diagnosis?
What is the best therapy for this condition?
ANSWERS TO CASE 46: Necrotizing Soft Tissue Infections
Summary: A 48-year-old man with alcoholic cirrhosis presents with necrotizing soft tissue infection (NSTI) following a trivial injury to the left leg.
• Most likely diagnosis: NSTI.
• Best therapy: Early initiation of appropriate antibiotics and radical surgical debridement of necrotic tissue. The treatment outcome is adversely affected by delays in therapy.
1. Learn to recognize the clinical presentation and diagnostic strategies for NSTI.
2. Understand that rapid, aggressive surgical debridement is crucial in the treatment of NSTI.
3. Become familiar with the bacteriology of NSTI and appropriate antimicrobial choices for these conditions.
A patient with alcohol-induced cirrhosis, in an immunocompromised state, presents with a high fever, soft tissue edema, and leg pain out of proportion to the physical findings, all of which strongly suggest the possibility of severe soft tissue infection. These findings are not specific for NSTI and may be compatible with a deep-seated abscess. The patient reports receiving minor trauma to his leg prior to the onset of leg pain, which favors the diagnosis of NSTI over that of an abscess. The development of NSTI following trivial soft tissue trauma is typical of infections caused by gram-positive skin flora, including group A β-hemolytic Streptococcus. Because NSTI frequently involves mixed bacterial organisms, the initial antibiotic regimen for this patient should include broad-spectrum antibiotics directed against gram-positive, gram-negative, and anaerobic bacteria. Following initial resuscitation, the patient should undergo examination of the leg with exploration of the subcutaneous tissue for infection and tissue viability. Once the bacteriologic findings from the operative drainage/debridement become available, the antibiotic regimen can be modified to cover the specific pathogens identified.
Distant end-organ dysfunction such as acute respiratory insufficiency, acute renal insufficiency, and acute liver insufficiency may occur with NSTI; therefore, most patients should be treated in the intensive care unit with careful monitoring and maximal supportive care. The systemic consequences of NSTI can develop because of overwhelming sepsis and from circulating toxins (associated with Staphylococcusand group A Streptococcus toxic shock syndrome [TSS]).
Surgical debridement for this patient should begin with an incision over the involved soft tissue and an inspection of the subcutaneous tissue for gross evidence of necrosis and adherence to the underlying fascia. Easy separation of the subcutaneous tissue from the underlying fascia indicates microvascular thrombosis and necrosis and should be treated by tissue debridement.
Because of the rich blood supply to the skin, patients with NSTI generally do not develop skin necrosis and bullous changes until late in the disease process. It should be recognized that the absence of skin abnormalities is one of the leading factors contributing to delays in the recognition of NSTI. When identified, all necrotic tissue should be excised. The fascia commonly serves as a natural barrier to the infectious processes; involvement below the fascia occurs infrequently except during infections by Clostridium species. Patients whose conditions do not respond appropriately to supportive care, antibiotics therapy, and surgical debridement should be reassessed; the lack of improvement may be related to inadequate debridement and/or inappropriate antibiotic selection (source control).
APPROACH TO: Soft Tissue Infection
CELLULITIS: A milder form of soft tissue infection without the association of microvascular thrombosis and necrosis. Clinically, patients do not exhibit signs of systemic toxicity and can be adequately treated with antibiotic therapy.
NECROTIZING SOFT TISSUE INFECTION (NSTI): Soft tissue infection that affects primarily the dermis and subcutaneous tissue.
Early manifestations include the extension of edema beyond the spread of erythema and severe pain. Late clinical manifestations may include crepitation, the formation of skin vesicles, cutaneous anesthesia, and focal necrosis. CT scans and magnetic resonance imaging (MRI) are helpful in differentiating NSTI from cellulitis. The diagnosis of NSTI in most cases can be established on the basis of clinical evaluation (Table 46–1). Adjunctive imaging studies should not be obtained if they would lead to additional delays in surgical therapy. A definitive diagnosis can be achieved on the basis of needle aspiration of the involved tissue, Gram stain evaluation, or exploration and visualization of the subcutaneous tissue under anesthesia. The infection is associated with spreading thrombosis of the blood vessels in the subcutaneous fat and dermis, leading to tissue necrosis and poor antibiotic penetration into the affected tissue. NSTI can involve a variety of bacterial organisms. Optimal treatment consists of systemic antibiotic administration, surgical debridement, and supportive care.
Table 46–1 • CLINICAL MANIFESTATIONS OF NECROTIZING SOFT TISSUE INFECTION
Group A β-Hemolytic Streptococcus Soft Tissue Infection: Referred to in the lay press as the “flesh-eating infection,” this form of NSTI frequently occurs in patients with a compromised immune status (alcoholics, diabetic patients, and the malnourished); however, it can also occur in healthy individuals following trivial soft tissue trauma. Approximately 75% of cases are community acquired. Bacteremia and/or TSS develops in approximately 50% of patients. The local process generally spreads rapidly over the course of hours to days. The combination of clindamycin and penicillin has been touted to produce superior results compared to the use of the penicillins alone. There is limited evidence suggesting that therapy with intravenous immunoglobulins (Ig) neutralizes the bacteria-produced superantigens and may improve patient outcome.
Toxic Shock Syndrome: A clinical syndrome caused by pyrogenic toxin superantigens produced by staphylococcal organisms or group A β-hemolytic Streptococcus. The binding of superantigens to major histocompatibility complex class III molecules leads to T-cell clonal expansion and a massive release of proinflammatory cytokines by macrophages and T cells. Patients with TSS frequently develop mental obtundation, hyperdynamic shock, and multiple-organ dysfunction syndrome. The systemic findings in TSS frequently do not correlate with the local extent of the soft tissue (vaginal) infection and thus can cause a delay in diagnosis and treatment.
Fournier Gangrene: A specific form of scrotal gangrene first described by Fournier in 1883. Anaerobic streptococci are the predominant causative organisms, with secondary infection caused by gram-negative organisms. Strictly speaking, the term “Fournier gangrene” refers to the anaerobic Streptococcus-related scrotal infection but is frequently inappropriately applied to gram-negative synergistic soft tissue infections of the perineum and groin.
46.1 A 55-year-old man with diabetes presents with a swollen, painful right hand that developed 1 day after he sustained a puncture wound to the hand while fishing in the Gulf of Mexico. His temperature is 39.5°C (103.1°F), pulse rate 120 beats/min, and blood pressure 95/60 mm Hg. His right hand and forearm are swollen, and a puncture wound with surrounding ecchymosis is present on the hand. There is drainage of brown fluid from the wound. Which of the following therapies is most appropriate?
A. Supportive care, penicillin G, and hyperbaric treatment
B. Supportive care, penicillin G/tetracycline/ceftazidime, and surgical debridement
C. Supportive care, penicillin G/tetracycline/ceftazidime, surgical debridement, and hyperbaric treatment
D. Supportive care, penicillin G plus clindamycin, and intravenous Ig
E. Supportive care and penicillin G
46.2 A 62-year-old man with diabetes returns to the emergency department 3 days after undergoing incision and drainage of a perirectal abscess. The patient complains of fever and malaise. Evaluation of the perirectal area reveals an open, draining wound with a 20-cm area of surrounding induration, erythema, localized areas of blister formation, and skin necrosis. The infection has extended to involve the perineum, scrotum, and anterior abdomen. Which of the following is most likely represented by the process in this patient?
A. Fournier gangrene
B. Clostridial gas gangrene
C. NSTI caused by group A β-hemolytic Streptococcus
D. Polymicrobial synergistic NSTI
46.3 A 33-year-old house painter sustained an abrasion and superficial laceration of the left shoulder 2 days ago. He presents to the outpatient clinic with an area of erythema extending 3 cm along the area of skin abrasion and superficial laceration. There is an area of fluctuance beneath the area, and the tenderness does not appear to extend beyond the area. His temperature and vital signs are normal. Which of the following is the most appropriate treatment?
A. Incision and drainage of the area, followed by 1-week course of oral antibiotic therapy
B. Incision and debridement of the soft tissue infection
C. Oral antibiotics therapy for 1 week
D. Topical antibiotic ointment application and dressing changes
E. Oral antibiotics for 3 days followed by reassessment and drainage if needed
46.4 A 38-year-old man with a history of injection heroin abuse presents to the emergency center with circumferential tender and tense swelling over his left upper arm. The entire area is minimally erythematous but exquisitely tender. He indicated that he had injected some “black tar heroin” into the area 6 days ago. His temperature is 39.5°C (103.1°F), heart rate 125 beats/min, and WBC 46,000/mm3. Ultrasound of the upper extremity revealed no evidence of venous thromboses or soft tissue fluid collections. Which of the following is the most appropriate treatment?
A. Admit the patient to the hospital for IV antibiotics therapy for his severe cellulites, and, if this does not improve, repeat the ultrasound to look for an abscess.
B. Perform radical debridement of the affected area.
C. Perform a transesophageal echocardiography to rule out endocarditis and treat with systemic IV antibiotics.
D. Perform radical debridement of the affected area, followed by IV antibiotics therapy.
E. Administer IV antibiotics and hyperbaric therapy.
46.1 B. Supportive care, penicillin G/tetracycline/ceftazidime, and debridement are appropriate initial treatment for a patient who develops severe NSTI in an injury with the potential for Vibrio infection (acquired while fishing).
46.2 D. Polymicrobial synergistic infection is the most likely diagnosis based on the duration of events and location and the distribution of soft tissue infection.
46.3 A. This patient’s history and clinical presentation are compatible with having a superficial soft tissue abscess and some surrounding cellulites. Incision and drainage of the abscess should adequately address the abscess, and the course of antibiotic therapy should be enough to address the surrounding cellulitis. Either drainage alone or antibiotics alone may not be sufficient to address the problems this patient has.
46.4 D. This patient has a classic presentation of NSTI, that is pain and soft tissue changes beyond skin erythema. Based on history, the cause of the NSTI is related to the injection of illicit drugs that may be contaminated with soil or skin bacterial flora, and this form of NSTI is commonly associated with systemic inflammatory changes that this patient has already manifested. Treatment for this individual would consist of debridement of the affected soft tissue in addition to systemic antibiotics.
The most common findings in a patient with NSTI are local edema and pain in the presence of systemic signs such as high fever (hypothermia in some patients), tachycardia, and frequently mental confusion.
NSTI should be suspected when pain and tenderness extend beyond the area of skin erythema.
When NSTI is strongly suspected, exploration of the wound through a limited skin incision may help establish the diagnosis in a rapid fashion.
Rapid, aggressive surgical debridement is the most important treatment for NSTI.
Lack of improvement after treatment of NSTI may be related to inadequate debridement and/or inappropriate antibiotic selection (source control).
Bulger EM. Necrotizing skin and soft tissue infection. In: Cameron JL, Cameron AM, eds. Current Surgical Therapy. 10th ed. Philadelphia, PA: Elsevier Saunders; 2011:662-665.
Cole P, Heller L, Bullocks J, Holloer LH, Stahl S. Skin and subcutaneous tissue. In: Brunicardi FC, Andersen DK, Dunn DL, et al, eds. Schwartz’s Principles of Surgery. 9th ed. New York, NY: McGraw-Hill; 2010:405-421.