What X-ray finding is described as a "lead pipe" appearance of the colon?

The "lead pipe" appearance of the colon is most commonly associated with ulcerative colitis. This characteristic finding on X-ray is due to the loss of the haustral markings in the colon, which occurs because of the inflammation and ulceration caused by the disease. In ulcerative colitis, the inflammation typically affects the mucosal layer of the colon, leading to a smooth, straight-edged appearance of the bowel on imaging, resembling a lead pipe.

This appearance contrasts with other conditions affecting the colon. In diverticulosis, one would typically expect to see diverticula or outpouchings of the colonic wall rather than a uniform appearance. Colorectal cancer can create a mass effect or an irregularity, often presenting as a filling defect on imaging, which is distinct from the lead pipe appearance. Ischemic colitis might show areas of decreased perfusion or changes due to necrosis, but it does not lead to the same smooth, uniform appearance seen in ulcerative colitis.

Thus, the "lead pipe" appearance is specifically indicative of the changes in the colon due to ulcerative colitis, highlighting the pathological process involved in this inflammatory bowel condition.