Gastritis

Gastritis is the term used to describe inflammation of the lining of the stomach.
The stomach is part of the digestive system that receives ingested food from oesophagus and after partial digestion it passes the food to the small intestine. The stomach is a bag like structure which has a muscular outer wall and a folded inner wall. This allows the stomach to expand when filled with food and to shrink when empty.

The stomach

The stomach is lined with glands which excrete hydrochloric acid, a digestive enzyme called pepsinogen and intrinsic factor which is important in the absorption of vitamin B12. Glands also secrete mucous to protect the lining of the stomach from the acid and digestive enzymes. The muscles of the stomach churn the contents to aid digestion, and pump the food into the small intestine. Entry of food into the stomach is controlled by a muscular valve called the oesophageal sphincter, and exit is controlled by a similar valve called the pyloric sphincter.
Irritation or infection of the stomach lining causes an inflammatory response with destruction of gastric glands and mucous secreting cells. It may also damage the hormone releasing cells which control digestion.
There are a number of possible causes of gastritis including the following

• Helicobacter pylori. Infection of the stomach lining with this organism is one of the commonest causes of gastritis. H pylori is partially resistant to the hydrochloric acid secreted by the stomach and is able to colonise the mucous layer. Once established in this protective environment it may burrow down to infect and destroy the acid secreting parietal cells. This causes an increase in the release of the hormone gastrin which stimulates acid secretion in non-infected areas of the stomach. The increasing gastric acid secretion may overwhelm the stomach defences and cause tissue damage and erosion, particularly in the pyloric antrum and the duodenum. This may result in formation of an ulcer.

• Autoimmune gastritis. In some individuals the immune system attacks the parietal cells and the intrinsic factor required for absorption of vitamin B12. This may trigger the same damaging sequence of events described above. Failure to absorb vitamin B12 may result in pernicious anaemia.
• Chronic reactive chemical gastritis. Commonest causes are long term ingestion of nonsteroidal anti-inflammatories (aspirin, ibruprofen, naroxen etc) or excessive alcohol consumption.
• Non-infectious granulomatous gastritis. This is usually associated with chronic diseases such as Crohns or sarcoidosis.
• Ischemic gastritis. This is believed to be a result of obstruction or blockage of the blood vessels which supply the affected area of the stomach.