Conceivable mechanisms by which Helicobacter pylori provokes duodenal ulcer disease

A conceivable concept for the development of duodenal ulcers in Helicobacte r pylori (H. pylori) infected subjects is presented in this chapter. The co ncept includes an explanation of the fact that only a minority of all H. py lori-infected subjects will develop a duodenal ulcer. Helicobacter pylori i nfection of the antrum induces a hypersecretion of gastric acid secretion, giving rise to gastric metaplasia in the duodenal bulb. This gastric metapl asia is a prerequisite for H. pylori colonization of the bulb. These events are common to all H. pylori-infected subjects. However, a much higher dens ity of H. pylori bacteria and colonization with virulent organisms has been found in the bulb of duodenal ulcer patients, resulting in a much stronger inflammatory reaction with active duodenitis and an impaired bicarbonate s ecretion. These characteristics, together with acid hypersecretion, seem to be the important factors in evoking a duodenal ulcer.