Evaluation of submucosal lesions of the large intestine: part 2. Nonneoplastic causes.

Various nonneoplastic entities may manifest as submucosal abnormalities at colorectal evaluation, and it may be difficult to distinguish between those with an intramural origin and those with an extramural origin on the basis of optical colonoscopy alone. Cross-sectional radiologic imaging, which allows evaluation of the entire bowel wall and the surrounding tissues, plays an important role in the localization and characterization of these abnormalities. However, some superficial submucosal lesions that are initially detected at computed tomographic colonography or barium enema studies may be better characterized with colonoscopy; thus, it is important to recognize the complementary uses of these diagnostic tests. In addition, modalities such as transrectal ultrasonography and magnetic resonance imaging may be useful for the identification and characterization of some abnormalities. For timely and effective management, it is especially important that submucosal neoplasms of the large intestine be accurately distinguished from nonneoplastic entities such as lymphoid polyps, vascular lesions, and cystic lesions, as well as from extracolonic abnormalities (eg, endometriosis, uterine fibroids) and normal extracolonic structures (eg, uterus, vasculature). RSNA, 2007