Gastritis occurs when the inner lining of the stomach becomes inflamed, generally when its defenses against acidic digestive juices break down. Gastritis may occur suddenly or gradually. The most common form of gastritis is erosive gastritis, in which acid and/or other factors inflame, damage and wear down the stomach lining.

Gastritis can be caused by a number of factors, including infections, medications and stress. The most common causes are infections with the bacteria Helicobacter pylori (H. pylori) and the use of certain pain relievers called nonsteroidal anti-inflammatory drugs (NSAIDs). Both of these factors may irritate the stomach lining.

The most common symptoms of gastritis are pain or discomfort in the upper abdomen and indigestion. For most patients, symptoms are not severe and gastritis is not a serious condition. However, complications may arise. The most common complications are ulcers. In rare instances, gastritis may lead to cancer of the stomach.

Gastritis is typically diagnosed following a physician’s evaluation of the patient's medical history, a physical examination and a series of diagnostic tests (e.g., endoscopy, blood tests). The biopsy of a tissue sample obtained during endoscopy may provide a definitive diagnosis of gastritis.

For most patients, gastritis improves quickly with treatment. Medications and diet changes are usually all that is required to alleviate the symptoms of gastritis. Medicines that neutralize or block the production of stomach acids and those that protect and heal stomach tissues are the most frequently used. When gastritis is caused by an infection, antibiotics may be used, typically in combination with other medications. Physicians, often gastroenterologists, may recommend a bland diet for patients with gastritis. For some severe and uncommon types of gastritis, part of or all of the stomach may need to be surgically removed.