Gastritis describes inflammation of the stomach associated with mucosal injury. The most common causes are infectious (Helicobacter pylori), medication induced (NSAIDs, aspirin), or autoimmune.

Symptoms are typically mild to moderate in severity but persistent, primarily characterized by nausea, a dull epigastric pain, and occasionally emesis and bloating.

Depending on the etiology, gastritis can occur in a wide range of the population and at any age. Suspicion for gastritis should be highest in patients with classic symptoms and a history of excessive NSAID use or heavy alcohol consumption (see alcohol use disorder). Helicobacter pylori is seen in increased prevalence in individuals of Asian descent.