Helicobacter pylori and disturbance of gastric function associated with duodenal ulcer disease and gastric cancer.

Helicobacter pylori is now recognized as the major acquired factor in the pathogenesis of duodenal ulcer disease (DU). There is also an association between H. pylori infection and the subsequent development of gastric cancer. The mechanisms by which such infection predisposes the host to these diseases are incompletely understood, but disorders induced by the bacterium in gastric function play a pivotal role. In most patients, H. pylori infection stimulates acid secretion, leading to a predisposition to DU development. However, in some patients, the infection is associated with a significant decrease in acid secretion, a predisposition to gastric cancer. These divergent effects of H. pylori on gastric acid secretion explain the early conflicting reports on changes in acid secretion associated with the infection. The reason why H. pylori infection produces divergent effects on gastric acid secretion is unclear, but may be related to differences in bacterial strains or genetic, dietary or other environmental factors.