Peptic Ulcer Disease By Nimish Vakil, MD, University of Wisconsin School of Medicine and Public Health Reviewed / Revised Mar 2023 View Patient Education Etiology Symptoms and Signs Diagnosis Complications Treatment Key Points More Information Topic Resources Duodenal Ulcer Gastric Ulcer Gastric Ulcer Perforation Free Air CT With Free Peritoneal Air A peptic ulcer is an erosion in a segment of the gastrointestinal mucosa, typically in the stomach (gastric ulcer) or the first few centimeters of the duodenum (duodenal ulcer), that penetrates through the muscularis mucosae.