[When is H pylori a cause of duoenal ulcer? Hypersecretion of gastric acid, active duodenitis and reduced bicarbonate secretion are links in the chain].

Helicobacter pylori infection engaging mainly the gastric antrum causes hypersecretion of gastric acid. The increased duodenal acid load gives rise to islands of gastric mucosa in the proximal duodenum. As these bacteria thrive only on gastric mucosa it presents an opportunity for Helicobacter pylori to colonize the duodenum. A much higher density of virulent Helicobacter pylori has been found in the duodenum of duodenal ulcer patients in comparison to infected subjects without duodenal ulcer. The high density of virulent Helicobacter pylori in the proximal duodenum results in a strong inflammatory reaction with active duodenitis and impaired bicarbonate secretion. These characteristics of duodenal ulcer patients, together with the acid hypersecretion, seem to be the key factors in evoking a duodenal ulcer.