Evaluation of submucosal lesions of the large intestine: part 1. Neoplasms.

At luminal evaluation of the large intestine, any masslike protrusion that is covered by normal mucosa, whether the underlying process is intramural or extramural in origin, may be reported as a submucosal lesion. The full characterization of submucosal lesions may be difficult with optical colonoscopy alone, and endoscopic biopsy is often nondiagnostic. Cross-sectional radiologic imaging studies allow evaluation of the entire thickness of the bowel wall and surrounding tissues and often provide additional information with regard to lesion origin, internal composition, and extent of disease. Likewise, it may be difficult to distinguish submucosal lesions from mucosal polyps on radiologic images, and optical colonoscopy may provide complementary information about superficial submucosal soft-tissue lesions that are detected at computed tomographic (CT) colonography or barium imaging. Depending on the specific clinical situation, colonoscopy, CT colonography, transrectal ultrasonography, and magnetic resonance imaging all may play an important role in the diagnostic evaluation of submucosal lesions of the large intestine. It is important that radiologists be familiar with the multimodality imaging appearances of such entities so that neoplasms--especially those that are malignant--can be accurately identified and characterized and effectively managed. RSNA, 2007