Pneumomediastinum and subcutaneous emphysema of the neck occur exceptionally in spontaneous, retroperitoneal perforation of the sigmoid colon. These signs, in association with a septic syndrome and multiple organ failure, mandate the search of a gastrointestinal tract perforation, even in the absence of digestive symptoms. Careful deep palpation of the abdomen may determine the abdominal origin of the septic focus and thereby provide justification for exploratory laparotomy without further diagnostic investigations.