Role of Helicobacter pylori in gastritis and duodenitis in man.

Although Helicobacter pylori is now accepted as the major aetiological factor in chronic gastritis in man, many of the factors which determine its pathogenicity are unknown. The organism has adapted to survive in the low-pH environment of the stomach, partly through its ability to buffer hydrogen ion by the hydrolysis of urea and by the presence of lectins on its surface, which bind to gastric mucosa and epithelial cells. After attachment, harmful toxins and enzymes have access to the gastric cells and cellular damage and an immune response ensues. In patients with duodenal ulceration, Helicobacter pylori-related gastritis predominantly affects the gastric antrum and has a high prevalence. Excessive gastrin production has been suggested as a potential aetiological factor linking infection with duodenal ulcer development. Perhaps more important is the association between gastric metaplasia of the duodenal epithelium, which is correlated with acid load and is more extreme in H. pylori positive patients with duodenitis. Organisms may subsequently spread from the gastric antrum into areas of gastric metaplasia in the duodenal bulb, leading to areas of chronic duodenitis and ultimately frank ulceration. It should not be overlooked, however, that other factors such as genetic predisposition, blood group, stress, drugs and smoking all have a role to play in the outcome, given the comparatively small number of patients in the general population infected with H. pylori who develop ulcer disease.