The colon cutoff sign describes aeric distension of the proximal colon with abrupt termination of gas at the level of the splenic flexure, associating decompression of the distal colon.
It has been originally described in abdominal radiographs, but it can also be seen in CT scans.
It is classically seen in acute pancreatitis, because of extension of the inflammation through the phrenico-colic ligament, which causes spasm and narrowing at the splenic flexure.
It can be also seen in colonic carcinoma (see case report on NEJM) or mesenteric ischemia.