[Gas gangrene secondary to carcinoma of the colon].

Systemic infections due to enteric bacteria can develop in patients with occult intestinal tumours. A patient with a sigmoid adenocarcinoma that developed crepitation and necrosis of soft tissues in gluteous region and thigh of left lower limb is presented. No pus or free fluid was observed in the peritoneal cavity; a sigmoid tumor infiltrating and perforating the retroperitoneum with necrosis of the psoas muscle was found. The infection spread subsequently through the inguinal canals and sciatic foramen to the lower limb. Necrotizing infections of soft tissues without previous trauma or ischemic accident leads to the suspicion of an occult digestive disease.