Colonoscopy in unexplained lower gastrointestinal bleeding.

Two hundred and forty patient with unexplained gastrointestinal blood loss underwent colonoscopy. Significant lesions which were thought to be likely causes of bleeding were identified in 98 patients, ie, 41% of total, which included active colitis in 9%, large polyps in 10% and colorectal cancer in 12% of patients. Of the cancers found at colonoscopy, 64% were Dukes A or B. This study confirms the role of colonoscopy in the investigation of unexplained chronic lower gastrointestinal bleeding.