Gastric and duodenal ulcers are painful erosive lesions ofthe mucosa that may extend to deeper layers. Such ulcerscan occur anywhere between the lower esophagus and thejejunum, and their causes include bacterial infections withHelicobacter pylori, effects of nonsteroidal anti-inflammatorydrugs, overproduction of HCl or pepsin, and loweredproduction or secretion of mucus or bicarbonate.