Gastritis means inflammation of the stomach lining, particularly the gastric mucosa. The term is sometimes used loosely to describe any stomach discomfort, but medically it refers to an inflammatory pathological process that can be acute or chronic and can have several causes. Acute gastritis may develop rapidly after exposure to irritants or severe physiological stress, whereas chronic gastritis can persist for prolonged periods and produce progressive changes in the gastric mucosa.
Gastritis may be identified histologically on biopsy even when a person has few or no symptoms. Conversely, upper abdominal pain, nausea or indigestion does not by itself prove that gastritis is present. This distinction between symptoms and tissue inflammation is important because dyspepsia, gastritis and peptic ulcer disease are related but not interchangeable concepts.
Helicobacter pylori is one of the most important causes of chronic Gastritis worldwide. This bacterium colonises the stomach and has adaptations that allow it to survive the acidic gastric environment. Persistent infection can produce chronic active inflammation and alter gastric physiology. Over time, some infected individuals develop atrophic gastritis and intestinal metaplasia, changes associated with increased risk of gastric adenocarcinoma. H. pylori is also strongly associated with peptic ulcer disease and certain gastric lymphomas.
Another major cause of chronic gastritis is autoimmune gastritis, in which immune-mediated destruction of acid-producing parietal cells can result in reduced gastric acid secretion and impaired intrinsic-factor production. Loss of intrinsic factor can cause vitamin B12 deficiency and eventually neurological or haematological consequences. These distinct mechanisms demonstrate why identifying the cause of gastritis matters for both immediate management and long-term risk.
Acute Gastritis can result from substances or circumstances that injure or disrupt the gastric mucosal barrier. Non-steroidal anti-inflammatory drugs can reduce protective prostaglandin activity, impairing mucosal defence and increasing susceptibility to acid-related injury. Excessive alcohol exposure can directly irritate gastric tissue, while severe physiological stress associated with critical illness, major trauma, burns or certain systemic conditions can contribute to stress-related mucosal injury. Bile reflux and some other chemical irritants can also damage the stomach lining.
Inflammation may coexist with erosions or bleeding, and severe cases can cause haematemesis or black stools. The stomach normally protects itself through mucus and bicarbonate secretion, epithelial tight junctions, mucosal blood flow and prostaglandin-mediated mechanisms. Gastritis develops when these protective systems are overwhelmed, disrupted or targeted by an inflammatory process.
Chronic Gastritis can produce structural changes in the stomach over time. H. pylori-associated inflammation may progress through stages involving gland loss and intestinal metaplasia, particularly in susceptible individuals. Autoimmune gastritis preferentially affects the body and fundus of the stomach and can cause loss of parietal cells, reduced acid production and elevated gastrin concentrations. Chronic gastric inflammation can therefore affect digestion, micronutrient absorption and the risk of specific malignancies.
Vitamin B12 deficiency associated with autoimmune gastritis can produce megaloblastic anaemia and neurological abnormalities if untreated. Iron deficiency can also occur in some forms of chronic gastritis. Because chronic gastritis may be asymptomatic, its presence can occasionally be discovered during investigation for anaemia, dyspepsia or another condition. Histological classification helps distinguish different patterns and causes, making biopsy interpretation an important component of specialist assessment when endoscopy is performed.
Symptoms of Gastritis can include upper abdominal discomfort, nausea, vomiting, early satiety and reduced appetite, but symptoms are neither universal nor specific. Some people with substantial histological inflammation have minimal symptoms, while others with prominent dyspepsia have little or no objective gastric inflammation. Bleeding can occur when inflammation produces erosions or ulceration, leading to vomiting of blood or passage of black, tarry stools. Severe bleeding requires urgent medical assessment because gastrointestinal haemorrhage can cause anaemia, circulatory compromise and other complications.
Gastritis can also coexist with peptic ulcer disease, making it difficult to determine which lesion is responsible for symptoms without endoscopic assessment. Persistent or unexplained symptoms should therefore be interpreted alongside medication history, H. pylori status, nutritional findings and other gastrointestinal investigations rather than diagnosed solely from symptom descriptions.
Diagnosis of Gastritis may involve non-invasive testing or direct examination of the stomach. H. pylori can be assessed using breath testing, stool antigen testing or other validated methods, with the choice depending on circumstances and recent medication exposure. Upper gastrointestinal endoscopy allows visual assessment of the gastric mucosa and biopsy sampling. Histology can identify inflammatory patterns, H. pylori organisms, glandular atrophy, intestinal metaplasia and features suggestive of autoimmune disease.
Blood tests can identify consequences such as iron deficiency, vitamin B12 deficiency or anaemia and may assist in evaluating autoimmune gastritis. Acid-suppressing medicines and antibiotics can interfere with certain H. pylori tests, so testing protocols often require appropriate medication intervals to reduce false-negative results. Diagnosis should therefore establish both the presence and, where possible, the cause of gastric inflammation because eradication, medication adjustment, nutritional replacement and surveillance requirements differ.
Treatment of Gastritis is directed towards the underlying cause and the severity of mucosal injury. H. pylori-associated gastritis is treated with an eradication regimen combining appropriate antibiotics with acid suppression or other acid-lowering therapy, with the precise regimen influenced by antibiotic resistance patterns and treatment history. When non-steroidal anti-inflammatory drugs contribute to gastric injury, clinicians may consider stopping or modifying them where medically appropriate and using gastroprotective treatment when continued therapy is necessary.
Acid suppression can facilitate healing of acid-related mucosal injury, while removal of aggravating exposures such as excessive alcohol may reduce further damage. Autoimmune gastritis requires attention to nutritional consequences, particularly vitamin B12 deficiency, and may require long-term replacement. Treatment does not simply aim to suppress symptoms; eradication of H. pylori can reduce future ulcer and certain cancer risks, making causal treatment more significant than temporary relief alone.
Gastritis has a long history in medicine, but modern understanding has changed substantially with recognition of H. pylori and autoimmune mechanisms. Earlier theories often attributed stomach inflammation primarily to acid or dietary factors, whereas microbiological and immunological research demonstrated that persistent infection and autoimmunity can fundamentally alter gastric tissue. A key misconception is that all stomach pain represents gastritis, or that gastritis automatically means an ulcer.
Gastritis is inflammation, whereas an ulcer is a deeper mucosal defect extending through the epithelial surface into the underlying tissue. They can occur together but are not identical. Another misconception is that H. pylori infection is simply a short-lived stomach infection; untreated infection can persist for years. Understanding gastritis therefore requires linking symptoms with tissue pathology, recognising different causes and appreciating its relationships with ulcer disease, nutritional deficiency and gastric cancer risk.
