Anal verge and low rectal bleeding. A diagnostic problem.

We describe five patients with lower gastrointestinal bleeding with negative endoscopy who subsequently proved to have sources of bleeding in the rectum close to the anal verge. The failure to identify such sources of bleeding via the endoscope was due to endoscopic geometry within the rectum, limited colonic preparation possible in the massively bleeding bowel, endoscopic inexperience, and a low clinical suspicion for very distal lesions. We discuss appropriate application of the available diagnostic techniques and methods to avoid endoscopic diagnostic failures in low rectal hemorrhage.