Helicobacter pylori-negative gastritis: seek, yet ye shall not always find.

Since its recognition as the causative agent for most cases of gastritis, the prevalence of Helicobacter pylori-induced gastritis has been declining, in part due to the deliberate and inadvertent use of various medications. As a result, pathologists find themselves facing cases of gastritis in which, based upon history and histology, there are expected but undetectable H. pylori organisms. This review explores the 2 possibilities of false-negative and true-negative gastritides, including when and how to search for H. pylori, explanations for absent organisms in cases of true H. pylori gastritis, and other causes of gastritis that may mimic H. pylori infection. The latter group includes reactive gastropathy with focal activity, focally active gastritis and carditis, autoimmune gastritis, granulomatous gastritis, lymphocytic gastritis, and other infections.