Duodenal ulcer. Close-up of a portion of the duodenum (small intestine) showing a duodenal ulcer (round, dark red at centre), also known as a peptic ulcer. Peptic ulcers occur in the organs of the gastro-intestinal tract as a result of erosion by acidic gastric juice. They typically measure 10 to 25mm across and about 0.25mm deep. The symptoms are usually a burning or gnawing pain in the abdomen; in the case of a duodenal ulcer the pain may be temporarily relieved by eating. The most common complication is bleeding from the ulcer. The ulcer is treated with antacid and ulcer- healing drugs; surgery is performed if the ulcer does not respond to medication.