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 drainage of the abscess and debridement of the necrotic material. However, the patient’s condition deteriorated quickly before the surgical interventions were performed and slipped into septic shock. Emergency resuscitative measures were unsuccessful, and unfortunately, the patient died. The case represents a rare pathology with an unusual presentation, which can be fatal if diagnosis and treatment is delayed.

Xanthogranulomatous pyelonephritis (XGP) is a rare chronic suppurative granulomatous infection of the kidney associated with renal obstruction and progressive renal parenchymal destruction. We present an unusual clinically occult case of extensive right XGP which presented clinically with discharging right gluteal sinus and swollen right posterolateral chest and abdominal walls extending caudally to right gluteus. Contrast enhanced computed tomography of the abdomen and pelvis revealed obstructing right renal calculi, severe hydronephrosis, renal destruction and large (20.7 × 10.2 × 14.7 cm) abscess extending caudally to right gluteus. Histopathology of the specimen was concluded as right xanthogranulomatous pyelonephritis. This case demonstrates how distant an insidious XGP can infiltrate. It also emphasizes the need to have a broad range of differential diagnoses including XGP when presented with a case of gluteal abscess and sinus. Contrast enhanced computed tomography plays a key role in evaluating the cause, extent and complications of XGP and is also useful in pretreatment planning.

Aneurysmal dilatation of colon is a rare imaging feature of colon adenocarcinoma. Two cases with massive aneurysmal dilatation of the colon secondary to moderately differentiated adenocarcinomas are described. The 2 cases presented with asymmetric and progressive abdominal distension with no obstructive symptoms. Contrast-enhanced computed tomography of the abdomen and pelvis demonstrated marked aneurysmal dilatation of the involved segments of the colon and circumferential mural thickening. Colonoscopy found markedly dilated lumen in the involved segment of the colon. Histology of the biopsy specimens taken during colonoscopy revealed moderately differentiated adenocarcinoma with extensive infiltration of colon wall and damage of myenteric nerve plexus.