Acute haemorrhagic gastritis

 • Caused by an abrupt insult to the gastric mucosa.

 • Often the result of drugs or a severe alcohol binge, but any acute medical illness which reduces gastric blood flow may also cause acute gastritis.

 • endoscopy shows numerous punctate erosions which ooze blood.

 • Severe forms can cause significant upper GI haemorrhage.

• histology shows neutrophilic infiltration of the gastric mucosa with haemorrhage and mucosal necrosis.

 • Acute gastritis usually resolves rapidly and uneventfully.

 Autoimmune gastritis

 • Caused by autoimmune attack directed at parietal cells in fundic glands.

 • histology shows infiltration of the body mucosa by lymphocytes and plasma cells. the infiltrate is directed at fundic glands, with atrophy associated with loss of chief and parietal cells. Pyloric and intestinal- type metaplasia is common.

 • Increased risk of gastric neuroendocrine tumours (which arise on a background of neuro- endocrine hyperplasia and are often multiple) and carcinoma.

• Some patients also develop antibodies to intrinsic factor, leading to depletion of vitamin B12 and megaloblastic anaemia.

 Bacterial (Helicobacter) gastritis

 • A very common cause of gastritis which is usually antral- predominant.

• Most are caused by Helicobacter pylori, a curved flagellate Gram- negative rod.

• Helicobacter heilmannii, which is larger and more tightly coiled, accounts for <1% of cases.

• Histology shows a heavy lymphoid inflammatory infiltrate in the lamina propria, often with lymphoid follicle formation, with neutrophilic infiltration of the superficial mucosa. Infection may be associated with intestinal metaplasia and dysplasia.

 • the organisms can be identified on routine stains but are better visualized on special stains that highlight the bacteria.

 • In most cases, the gastritis is healed by eradicating the organism.

 • In a small proportion of untreated cases, the gastritis can be complicated by peptic ulceration, gastric carcinoma.

 Chemical/reactive gastropathy

 • Caused by any low- grade injury to the gastric mucosa.

 • Seen mostly in the antrum in relation to bile reflux or non- steroidal anti- inflammatory drugs (NSAIDs).

 • endoscopically, there is erythema of the gastric mucosa.

• histology shows vascular congestion, foveolar hyperplasia, and smooth muscle proliferation. Inflammation is minimal or absent. It is for this reason the term gastropathy is preferred to gastritis.

 • It usually resolves without complication if the offending cause is removed.

Iron pill gastritis

 • Caused by the corrosive effects of ingested iron tablets.

 • histology shows it causes acute inflammation with erosion or ulceration of the gastric mucosa. Yellow- brown iron pigment may be seen