PEPTIC ULCER

circumscribed lesion that occurs primarily in the mucous membrane of the stomach or duodenum (the upper segment of the small intestine); it is produced when external factors reduce the ability of the mucosal lining to resist the acidic effects of gastric juice (a mixture of digestive enzymes and hydrochloric acid). Until recently the factors responsible for peptic ulcers remained unclear; a stressful lifestyle and rich diet commonly were blamed. Evidence now indicates that infection with the bacterium Helicobacter pylori and long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) are the two major causes of peptic ulcer. Between 10 and 15 percent of the world's population suffers from peptic ulcer. Duodenal ulcers, which account for 80 percent of peptic ulcers, are more common in men than in women, but stomach ulcers affect women more frequently. The symptoms of gastric and duodenal ulcer are similar and include a gnawing, burning ache and hungerlike pain in the mid-upper abdomen, usually experienced from one to three hours after meals and several hours after retiring. In the early 1980s two Australian researchers, Barry Marshall and J. Robin Warren, challenged previous theories of ulcer development with evidence that ulcers could be caused by H. pylori. This theory was greeted with skepticism because it was thought that no organism could live in the highly acidic conditions of the stomach and duodenum. H. pylori overcomes this obstacle by converting the abundant waste product, urea, into carbon dioxide and ammonia, creating a more neutral local environment. Although the mechanism is not completely understood, this process causes the mucosal lining to break down. In its weakened condition the lining cannot withstand the corrosive effects of gastric acid and an ulcer can form. Infection with H. pylori is the most common bacterial infection in humans; it is pervasive in the Third World, and in the United States it affects about a third of the population. Among those who suffer from peptic ulcers, as many as 90 percent of those with duodenal ulcers and 70 percent with gastric ulcers are believed to be infected. Evidence also exists that untreated H. pylori infection may lead to stomach cancer. The recommended treatments for H. pylori-induced ulcers are two antibiotics, such as tetracycline and metronidazole, and bismuth subsalicylate or an antisecretory drug. Most peptic ulcers not caused by H. pylori infection result from the ingestion of large quantities of NSAIDs, which often are prescribed for conditions such as rheumatoid arthritis. Withdrawal of NSAID treatment usually allows the ulcer to heal, but if this is not possible the ulcer can be managed with antisecretory drugs such as the H2 blockers cimetidine and ranitidine (marketed as Tagamet and Zantac, respectively) and the proton pump inhibitor omeprazole (marketed as Losec or Prilosec). These drugs act by stopping the secretion of stomach acid. A small proportion of peptic ulcers results from the Zollinger-Ellison syndrome, an uncommon disease associated with a tumour of the pancreas, stomach, or duodenum that causes an increase in gastric acid secretion. Cigarette smoking has been found to have an adverse effect on peptic ulcers, slowing healing and promoting recurrence. Complications of ulcers include bleeding, perforation of the abdominal wall, and obstruction of the gastrointestinal tract.