Polypoid and pseudopolypoid lesions of inflammatory bowel disease: diagnosis on double-contrast enema.

The radiological and pathological features of ulcerative colitis (UC) and Crohn's disease (CD) are well known for most radiologists and gastroenterologists but on double-contrast enema, polypoid and pseudopolypoid manifestations of inflammatory bowel disease (IBD) often remain a source of major confusion. Inflammatory polyps project above the level of the surrounding mucosa. Pseudopolyposis is seen when extensive ulceration of the mucosa down to the submucosa results in scattered circumscribed islands of relatively normal mucosal remnants. Postinflammatory polyps reflect a non-specific healing of undermined mucosal and submucosal remnants and ulcers, and are mostly multiple. They have no malignant potential. Patients with long-standing UC and CD are at increased risk for developing colorectal carcinoma. Dysplasia is a precancerous histologic finding and is frequently seen in colitic colons at high risk for carcinoma. Dysplasia may be found in a radiographically normal appearing mucosa or it may be accompanied by a slightly raised mucosal lesion, a so-called dysplasia-associated lesion or mass (DALM lesion) and as a consequence radiographically detectable. Because differentiation of adenocarcinoma and dysplasia from inflammatory or postinflammatory polyps is sometimes difficult or impossible on double-contrast enema, endoscopy and biopsy are necessary for making a final diagnosis.