The radiological demonstraction of colorectal polyps undetected by endoscopy.

In a consecutive series of 800 routine double contrast studies of the colon, 119 polyps were diagnosed radiologically in 78 patients. Follow-up studies were available in 46 patients with 72 polyps. Ultimately, 56 of these polyps were confirmed (55 by endoscopy and 1 by repeat radiology). Six of these polyps had been missed on the initial endoscopic examination. The missed polyps are usually located in the rectum behind a valve of Houston or in any area of the colon where there is sharp angulation. Radiologists and endoscopists should be aware of these as potential endoscopic blind spots. These cases illustrate the importance of higg quality radiological study of the colon and the complementary nature of radiology and endoscopy in the detection of colorectal polyps.