Ruptured Obturator Internus Muscle Abscess Causing Extensive Retroperitoneal Necrosis

Obturator internus muscle (OIM) abscess occurs rarely in adults. Accurate diagnosis is often hindered and delayed due to the deep location of the abscess and the nonspecific clinical features. Even of rarer occurrence is rupture of the obturator internus muscle abscess into the perirectal space and retroperitoneum causing extensive retroperitoneal necrotizing soft tissue infection. We present a case of ruptured left OIM abscess, which initially presented with clinical features, which were suspected as acute pancreatitis. Contrast-enhanced multidetector computed tomography (MDCT) of the abdomen and pelvis revealed ruptured left OIM abscess with extensive fat stranding, fluid collections, and pockets of gas throughout the perirectal space, perisigmoid space, and bilateral posterior pararenal and anterior pararenal spaces as well as thickening of bilateral anterior renal fascia, posterior renal fascia, and lateral conal fascia. These CT findings were consistent with extensive retroperitoneal necrotizing soft tissue infection secondary to ruptured left obturator internus muscle abscess. Broad-spectrum antibiotics were instituted immediately, and the patient was urgently worked up for d