Bowel wall thickness as a differentiating feature between ulcerative colitis and Crohn's disease of the colon.

The colonic wall thickness was assessed from the plain abdominal radiograph and double contrast barium enema in 33 patients with ulcerative colitis, 28 with Crohn's colitis and 20 with neoplasia. The maximum wall thickness in the control group with neoplasia measured in non-diseased colon, was 2 mm. Accurate measurement was possible from only 34% of the plain films, owing to inadequate gas in the lumen. Measurement was possible in 84% of barium enemas, mainly in the descending colon. The maximum wall thickness associated with ulcerative colitis was 5 mm. In 50% of Crohn's colitis the wall thickness was above 5 mm. Estimation of the wall thickness was a slightly less sensitive index of the presence of colitis than the mucosal changes on double contrast enema. Distinction between the types of colitis was usually possible from the mucosal lesions. Where these could be similar, such as with confluent shallow ulceration, the tendency of Crohn's disease to be associated with a wall thickness in excess of 5 mm was valuable diagnostically.