Bedside ultrasound for the detection of diabetic myonecrosis

Diabetic myonecrosis is an uncommon complication of diabetes mellitus. There are fewer than 50 cases reported in the general medical literature. Patients classically complain of the abrupt onset of diffuse anterior thigh pain with no signs of overlying infection or signs of systemic toxicity. Because of the difficulty in diagnosis, most patients endure multiple medical visits until appropriate imaging modalities are obtained. Currently, magnetic resonance imaging (MRI) or tissue biopsy is considered the gold standard for diagnosis. This is the first case reported in the literature of diabetic myonecrosis detected in the ED by bedside ultrasound. We hope that with the continued use of bedside ultrasound, more physicians will be able to determine abnormal tissue architecture allowing for the early detection of diabetic myonecrosis. A 35-year-old woman with a history of insulin-dependent diabetes mellitus presented to the ED with complaints of left anterior thigh and right medial thigh pain for 10 days. The patient had been seen in the ED twice over a 4-day period and sent home with analgesics. The patient returned to the ED a third time for reevaluation after lack of pain relief. The patient denied injection drug use, erythema, or discharge from the overlying skin or any recent surgical interventions. On her third visit, the patient was noted to be in moderate pain. Initial vital signs were heart rate of 94 beats per minute, blood pressure of 155/90 mm Hg, temperature of 98.1°F, respiratory rate of 16 breaths per minute, and blood sugar of 123 mg/dL. The patient complained of continued bilateral thigh pain with no symptoms of systemic toxicity (fever, nausea, vomiting, etc). She stated the pain increased with activity and movement of either lower extremity. Old records showed normal white blood cell count and serum chemistries. A negative comprehensive ultrasound for the detection of deep venous thrombosis (DVT) was present in the medical record. Initial inspection of both legs showed bilateral swollen thighs with no overlying skin changes (Fig. 1A). Palpation demonstrated diffuse tender regions on the left anterior thigh and right medial thigh, with no areas of fluctuance. The neurovascular examination of the lower extremities was normal. The patient complained of pain with both passive and active knee and hip flexion. A focused bedside ultrasound exam was performed to evaluate the tender and swollen areas of the anterior left thigh and medial right thigh. The area was interrogated in both longitudinal and transverse planes with a high-resolution linear probe (5-10 MHz). The ultrasound exam demonstrated abnormal tissue architecture (Fig. 1B) in the left anterior thigh as compared to the contralateral anterior thigh. A deep soft tissue abscess was considered, but owing to the sharply delineated margins and extensive size of the abnormality on ultrasound, other diagnoses were included in the differential (pyomyositis and diabetic myonecrosis). Because of the inability to obtain a rapid MRI, an intravenous contrast computed tomography scan was performed demonstrating left rectus femoris and right semimembranous muscle enlargement with low attenuation throughout most of their course, with no discrete fluid collection (Fig. 1C). In conjunction with clinical signs and symptoms, the most consistent diagnosis was diabetic myonecrosis. The patient was admitted to the medical service for pain control and further diagnostic investigations. During her inpatient stay, an MRI of the lower extremities confirmed the diagnosis of diabetic myonecrosis (Fig. 1D). The patient continued to require narcotic analgesia for the next 10 days and was discharged from the medical service on tight glucose control. First described in 1965, diabetic myonecrosis is a rare complication of longstanding and poorly controlled diabetes. Most cases are misdiagnosed initially and there are no reported cases in the emergency medicine literature to date. Patients classically present with an acute onset of painful swelling in the affected muscle. The quadriceps compartment is the most frequently involved site. There is a slight predilection for females (1.7:1) and a strong association with the use of insulin for diabetic control. The pathologic mechanism is still debated, with some anecdotal data indicating an alteration of the coagulation-fibrinolytic system. Although most patients initially have an excellent recovery after bed rest and appropriate analgesia, 5-year mortality is high owing to severe underlying diabetic complications [1-3]. The diagnosis of diabetic myonecrosis is often very difficult. Physical exam reveals a swollen, tender leg without skin changes commonly present in infectious processes. Patients are generally afebrile and nontoxic appearing. Pulses are usually palpable, with strength and sensation unaffected. Movement may be limited because of the pain. The differential diagnosis is lengthy and includes DVT, muscle strain/rupture, pyomyositis, and soft tissue abscess. Plain radiographs may show soft tissue swelling, and comprehensive ultrasounds for DVT are only helpful to rule other causes. Magnetic resonance imaging and/or muscle biopsy is diagnostic, but rarely available in most emergency settings. Early recognition can be very difficult in the ED, but appropriate management can prevent further ED visits and nondiagnostic testing. Bedside ultrasound is readily available in the emergency setting, and with more evidence indicating the utility of this imaging modality in the evaluation of soft tissue infections, emergency physicians are becoming more familiar with normal and abnormal soft tissue architecture. Our patient's abnormal bedside ultrasound allowed rapid detection of a disease process that is commonly overlooked in the emergency setting, allowing directed diagnostic imaging and appropriate disposition.