Gastritis is an inflammatory process of the gastric mucosa that can be caused by a variety of conditions, commonly H. pylori infection or the use of drugs such as NSAIDs. Patients typically present with dyspepsia and can often be managed with a if there are no indications for an upper endoscopy. Depending on the results, patients receive eradication therapy or a trial of pharmacological acid suppression. Upper endoscopy and biopsy, which can identify histopathological signs of inflammation, are required for definitive diagnosis. Upper endoscopy is indicated in patients over 60 years of age and considered on a case-by-case basis when are present. Often, gastritis is diagnosed incidentally, when upper endoscopy is performed for other reasons. The underlying cause of gastritis may be obvious (e.g., direct injury from medication intake), but further testing may be required in order to identify the etiology and provide the optimal treatment.
- Gastritis: inflammation of the gastric mucosa, typically in response to H. pylori infection (H.pylori gastritis), direct injury (e.g., substance-induced gastritis), or as part of a systemic inflammatory disease 
- Gastropathy: injury to the gastric mucosa, usually involving a disruption in the protective mucous barrier. In contrast to gastritis, gastropathy is accompanied by little to no inflammation.
|Etiology of gastritis |
Helicobacter pylori infection is the most common cause of gastritis.
There are multiple classification systems for gastritis. There is significant overlap between different types, e.g., in the histopathological findings of acute and chronic gastritis. The most common types are described here. 
- Acute gastritis
- Chronic gastritis
- Atrophic gastritis
- Nonatrophic gastritis
- Erosive gastritis: multiple superficial erosions that do not extend beyond the muscularis mucosae and may occasionally cause bleeding
The differential diagnoses listed here are not exhaustive.
- Initial step: for most patients with upper GI symptoms, follow the .
Upper endoscopy and biopsies
- Indicated in patients > 60 years old
- Consider on a case-by-case basis if are present , or insufficient or no response to initial medical management
Additional studies: indicated based on individual evaluation and clinical suspicion
- Detecting complications: e.g., ↓ Hb and ↑ BUN/Cr ratio suggest GI bleeding
- Evaluating differential diagnoses: e.g., liver chemistries, lipase, amylase to screen for hepatic or pancreatic disease
- Identifying the underlying etiology: e.g., inflammatory markers or antibody testing if there is suspicion of systemic inflammatory disease or autoimmune disease
Esophagogastroduodenoscopy (EGD) with biopsies 
- Common findings include:
- Other endoscopic findings may be present in some types of gastritis (e.g., significant enlargement of mucosal folds in hypertrophic gastritis).
- Histopathologic findings: dependent on etiology
Chemical gastritis 
- Definition: direct chemical injury of the gastric mucosa that can be caused by drugs or other exogenous or endogenous substances. Patients often present with typical symptoms of gastritis. Nausea/vomiting and bleeding (e.g., melena) may also occur.
- Etiology: : Common causes include NSAIDs, aspirin , alcohol, caffeine, corrosive substances , certain supplements , and bile reflux.
- Pathophysiology: direct mucosal injury → edema → hyperemia → erosion → ulceration
- Complications: gastric ulcers → bleeding, perforation
Ménétrier disease 
- Definition: gastritis featuring massive enlargement of the mucosal folds
- Clinical features
- Diagnostics: based on endoscopic and histopathological findings
- Peripheral edema
- Malignant degeneration
- Granulomatous gastritis: the presence of multiple granulomas in the gastric mucosa due to infectious or noninfectious causes 
Eosinophilic gastritis: eosinophilic infiltration of the gastric mucosa with unknown etiology that is frequently associated with allergic diseases , blood eosinophilia, and ↑ IgE
- Clinical and endoscopic features are nonspecific. The diagnosis is confirmed with histopathology.
- Management: typically , , and an .
- Lymphocytic gastritis: lymphocytic infiltration of the gastric mucosa, not specific to any particular disease, that is likely due to autoimmune or allergic inflammation