Necrotizing soft-tissue infection (NSTI) often is difficult to distinguish from a superficial soft-tissue infection like cellulitis. Both conditions present with pain, edema, and erythema and can be accompanied by fever and malaise. The diagnosis of NSTI must be made quickly because successful treatment requires early surgical debridement and broad-spectrum antibiotics. The following case demonstrates the challenge of diagnosing NSTI.
A 50-year-old physician developed a sore throat with subjective fevers, night sweats, and chills. After 2 days, his symptoms resolved. The next day he developed right thigh pain while playing tennis and limped off the court. That night he had fevers, chills, and sweats. For the next 3 days, his right thigh pain persisted with waxing and waning fevers.
The patient’s medical history included gastroesophageal reflux disease, vitamin D deficiency, and a positive purified protein derivative test for which he had completed 1 year of isoniazid therapy. The patient was married and in a monogamous relationship with his wife. He had traveled to the Sierra National Forest and Yosemite Park during the preceding winter. He did not swim in a lake or recall a tick bite. He had not consumed raw food, imported meats, or dairy products. He recently started oral fluconazole for tinea corporis.
The patient’s temperature was 39.5°C, heart rate was 115 beats per minute, blood pressure (BP) was 142/88 mm Hg, and respiratory rate was 18 breaths per minute with an oxygen saturation of 95% while breathing ambient air. He was drenched in sweat yet remained comfortable throughout the interview. The oropharyngeal mucosa was moist without lesions or erythema. There was no rash or lymphadenopathy. The lungs were clear to auscultation. The cardiac exam revealed tachycardia. There was point tenderness to deep palpation of the mid-anterior right thigh without crepitus, erythema, or edema.
The patient’s sodium level was 129 mmol/L (normal range 135-145 mmol/L), bicarbonate was 20 mmol/L (normal range 22-32 mmol/L), creatinine was 1.1 mg/dL (normal range 0.7-1.2 mg/dL), and glucose was 194 mg/dL. The white blood cell count (WBC) was 12,900 cells/mm3 (normal range 3,400-10,000 cells/mm3) with 96% neutrophils. The hematocrit was 41% (normal range 41-53%), and the platelet count was 347,000 cells/mm3 (normal range 140,000-450,000 cells/mm3). The lactate level was 2.2 mmol/L (normal range 0-2 mmol/L). The creatine kinase level was 347 U/L (normal range 50-388 U/L), and the lactate dehydrogenase level was 254 U/L (normal range 102-199 U/L). A rapid group A streptococcal (GAS) antigen test was negative. A radiograph of the right femur revealed mildly edematous soft tissue. On ultrasound the right quadriceps appeared mildly edematous, but there was no evidence of abscess or discrete fluid collection (eFigure 1).
eFigure 1. Ultrasound of the Right Anterior Thigh Ultrasound revealed heterogeneous, mildly edematous quadriceps muscle. There was no abscess or discrete fluid collection. There was trace fluid along the fascia of the quadriceps muscle.
Four liters of normal saline, acetaminophen, ceftriaxone, and doxycycline were administered to the patient. Overnight he was afebrile, tachycardic, and normotensive. The following morning his BP decreased to 81/53 mm Hg. His WBC count was 33,000 cells/mm3 with 96% neutrophils. A peripheral blood smear showed immature granulocytes. The sodium and creatinine increased to 135 mmol/L and 1.3 mg/dL, respectively. The erythrocyte sedimentation rate was 20 mm/h (normal range 0-10 mm/h), and the C-reactive protein level was 174 mg/L (normal range < 6.3 mg/L).The right thigh became erythematous and edematous.
Given concern for necrotizing fasciitis, antibiotics were changed to vancomycin, piperacillin-tazobactam, and clindamycin. The patient was taken to the operating room (OR). The right quadriceps muscle was markedly edematous with overlying necrotic fibrofatty tissue with easy separation of the fascia from the anterolateral rectus femoris and rectus lateralis muscles. Necrotizing fasciitis was diagnosed.
The tissue was debrided, and surgical pathology revealed fibroadipose tissue with extensive necrosis and dense acute inflammation (eFigure 2). After the anterolateral space between the fascia and underlying thigh muscle was drained, a Penrose drain was placed, and the wound was left open with plans for a second-look operation within 24 hours.
eFigure 2. Surgical Pathology of Debrided Right Thigh
Pathology revealed fibroadipose tissue with extensive necrosis and dense acute inflammation.
eFigure 3. Right Anterior Thigh
Two Penrose drains inserted after second operation.
In the ensuing hours erythema extended proximal to the operative site. The patient was emergently taken to the OR. The focus of necrotizing fasciitis along the anterolateral aspect of the thigh had extended posteriorly and superiorly. This area was irrigated, all loculations were disrupted, and a second Penrose drain was placed.