In patients with bleeding duodenal ulcers, the endoscopic finding associated with the highest incidence of rebleeding is:

A. Visible vessel.

DISCUSSION: A visible vessel in an ulcer bed is associated with a 50% chance of rebleeding and, other than an actively bleeding vessel, is the worst endoscopic prognostic indicator for rebleeding. Cherry-red spot, adherent clot, and clean small ulcers all are associated with a lower incidence of rebleeding.