Intramural gas as a finding proximal to obstructing lesions of the colon has not been reported, although the association of ulceration and obstructing lesion has been previously noted (1, 5). The usual radiologic differential of intramural gas (4) includes necrosis (3) as is found with strangulated mechanical obstruction; mesenteric vascular occlusions; or toxic ulcerative colitis; necrotizing gastroen-terocolitis; and pneumatosis intestinalis. Van Zwalenburg's (6) early work developed the mechanism of strangulation from distension of hollow viscera. The pathogenic sequence is distension, with decrease in blood flow through the vessels extending from the mesenteric border to the bowel wall, mural thrombosis, ulceration, infection, and perforation. Hurwitz and Khafif (2) reported the importance of the condition of the tissues proximal to an obstructing lesion and its effect on the success of an anastomosis. The presence of intramural gas or ulceration with obstructing lesions should alert the surgeon to inspect carefully the anastomotic site. This includes utilizing the sigmoidoscope at surgery and extending the resection proximally until normal tissue is identified. On Aug. 11, 1967, a 47-year-old white female entered the hospital who had apparently been in good health except for chronic alcoholism, until the appearance of abdominal distension approximately four days earlier. Abdominal radiographs showed gaseous distension of the large and small bowel, with gas identified in the wall of the cecum (Fig. 1). A barium-enema study the next day demonstrated complete retrograde obstruction in the sigmoid, and thus the proximal bowel could not be seen. At surgery a mass obstructing the sigmoid colon was palpated, and a right transverse colostomy was carried out. While preparations were being made for the resection, thrombophlebitis developed, and the surgery was delayed. On Sept. 15, a sigmoid resection was performed for adenocarcinoma. No metastases were found. On Sept. 18, large amounts of purulent material drained from the wound. Dehiscence resulted, and the patient continued to do poorly. She died on Sept. 25 as a result of fulminating peritonitis with renal shutdown. Summary The recognition of intramural gas in addition to suggesting intestinal necrosis, pneumatosis intestinalis, and necrotizing gastroenterocolitis—should also alert the observer to the possibility of an obstructing lesion. The association of an obstructing lesion with proximal intramural gas necessitates careful selection of the surgical anastomotic site. the left ventricle was 15 mm thick, and the aorta was dilated and sclerotic. Microscopically, the esophagus showed chronic inflammation of the mucosa and submucosa; the liver nodules were composed of an anaplastic adenocarcinoma, whose epithelium in the better preserved portions resembled that of the biliary tract.