The differential diagnosis of Helicobacter pylori negative gastritis.

Gastric biopsies are often submitted with as clinical question Helicobacter pylori (HP) infection. Regularly, the morphology suggests a HP infection but the organism is not detected in special stains. This review presents a practical approach to deal with such biopsies. The first step is to exclude a false negative result of the search for HP, by ensuring that both antral and oxyntic mucosa are present, by the use of sensitive stains, identification of marked reactive changes, such as intestinal, pseudo-pyloric, pancreatic metaplasia that may suggest a diagnosis of (HP associated or autoimmune) atrophic gastritis, and finally identification of signs of the use of proton pump inhibitors (PPI) as in such biopsies, HP may sometimes be found only within parietal cells. The differential diagnosis should include lymphocytic gastritis, other diseases affecting the stomach, such as inflammatory bowel disease (IBD), vasculitis, granulomatous disease, viral infection, such as cytomegalovirus (CMV) or more rarely Epstein-Barr virus (EBV) infection, or other bacterial infections, such as Enterococcus and Treponema pallidum. Clinical input may be required to ensure the patient is not taking medication that may cause gastritis, such as antibiotics used for HP eradication or common medications that cause a form of gastropathy. When these have been excluded, a known cause has not been found and in such a case, the term idiopathic focal/diffuse gastritis can be used.