Gastritis is a group of conditions characterized by inflammation of the lining of the stomach (mucosa). The inflammation often results from ingestion of spoiled or contaminated foods, foreign objects, toxic plants, grass, bones, chemicals (detergents, antifreeze), and heavy metals (lead, zinc). Infectious, viral, and bacterial causes are quite rare in dogs. Gastritis may occur suddenly (acute gastritis) or it can occur slowly over time (chronic gastritis).
The stomach has a remarkable ability to withstand mucosal injury which is the result of a complex mucosal defence mechanism. This mechanism includes protective secretions (bicarbonate, mucus glycoproteins, prostanoids), mucosal blood flow, and mucosal immune system. Ingested bacteria, food antigens, and toxins may induce acute inflammatory response and overwhelm any or all of the components of the mucosal defense mechanism.1
Irritating drugs such as non-steroidal anti-inflammatory drugs (NSAIDs) continue to be one of the most common causes of acute gastritis and gastric erosive-ulcerative disease (GEU), particularly in dogs. Mucosal damage caused by NSAIDs is primarily the consequence of two effects:(1) NSAIDs cause direct damage to the gastric lining of the stomach; (2) NSAIDs inhibit the synthesis of protective chemicals called prostaglandins. All commonly used NSAIDs, especially ibuprofen, piroxicam, and flunixin, have the potential to cause these harmul effects. Ibuprofen, which owners frequently give to their pets thinking it is safe, is particularly dangerous because it undergoes enterohepatic circulation, which significantly prolongs the time before it is eliminated from the body compared with humans. The same is true for piroxicam.4
Vomiting is considered to be the hallmark of the disease. Food and bile are typically vomited with small amounts of blood. Abdominal pain and swelling may be present with higher than normal temperature. Diarrhea and weight loss are seen less frenquently. Affected dogs have no appetite and may or may not feel sick. Unfortunately, most owners do not distinguish between vomiting and regurgitation when describing the problem, and will often confuse vomiting with difficulty in swallowing, gagging or coughing. When feeding begins, small amounts of cool water are offered frequently. If the dog drinks without vomiting, small amounts of a bland diet (for example, 1 part cottage cheese and 2 parts potato; 1 part boiled chicken and 2 parts potato) are offered.
Although most patients with acute gastritis improve in 1 to 5 days, some patients require supportive therapy. Treatment mainly consists of providing parenteral fluid therapy (by route other than the alimentary canal), and withholding food and water for 24 hours to control vomiting. Antibiotics and corticosteroids are rarely indicated.3
Drugs used for medical management of gastritis include H2-receptor antagonists, proton pump inhibitors, cytoprotective agents, and prostaglandin analogues. Suppression of gastric acid promotes healing of the damaged mucosa and diminishes the damaging effects of pepsin, which is most active in an acid environment. Cytoprotectants and prostaglandin analogues strengthen mucosal defenses. Other drugs may be used to reduce gastric reflux and control vomiting, provide patient comfort and reduce fluid and electrolyte losses.4
Chronic gastritis is a condition characterized by chronic vomiting. It appears to occur frequently in the dog and cat and is usually suspected in any animals with chronic vomiting for which there is no diagnosis. Two forms occur: ulcerative and non-ulcerative. Ulcerative gastritis is usually associated with tumors. Chronic gastritis may be caused by dietary factors, interference with normal blood flow in the lining of the stomach (ischemia), excess hydrochloric acid production, reflux of bile and enzymes into stomach, autoimmune disease and release of antigens following physical damage.
Because inflammation impairs motility and delays emptying, animals with chronic gastritis may retain food in the stomach for long periods of time. A definite diagnosis of chronic gastritis requires mucosal biopsy which helps identify a specific form of gastritis:
- Lymphocytic-plasmacytic gastritis
- Eosinophilic gastritis
- Atrophic gastritis
- Hypertrophic gastritis
Chronic hypertrophic gastritis is a rare disorder characterized by thickened gastric folds which may be caused by chronic inflammation, foreign bodies or long-term drug administration. The condition has been documented in the Basenji, Boxer, Lhasa Apso, Shih Tzu, Maltese, and Pekingese dogs. The thickened gastric folds are inflamed, cause delayed emptying, vomiting, lethargy and loss of appetite.5 Eosinophilic gastritis is an uncommon disorder of an unknown cause characterized by diseased mucosa which may become ulcerated. This leads to bleeding. Atrophic gastritis is a rare disorder in which the gastric mucosa loses its secretory function. The cause is unknown, but the condition occurs mainly in older dogs and those animals with gastric reflux disease. The predominant complaint is chronic vomiting. Decreased amount of stomach acid leads to bacterial overgrowth in the small intestine which results in chronic diarrhea and loss of body weight and condition.
Some forms of gastritis may be caused by spiral bacteria of the genus Helicobacter which infects the stomachs of many mammalian species including humans, dogs, and cats. These gram-negative organisms produce urease, an enzyme that helps these organisms to adapt to the gastric environment and can be used diagnostically to confirm infection. Despite the high incidence of infection, most dogs and cats infected with Helicobacter do not develop gastritis.4
The underlying conditions should be managed first, if possible. Dietary management is based on the concept that food antigens are responsible for immune-mediated problems. Switching to an alternative protein to which a dog has not be exposed is a cornerstone of this concept. Commercial hypoallergenic diets such as Hill's Prescription Diet z/d, Iams Response FP, Waltham Hypersensitivity Control, Purina Limited Antigen brand formula are very useful. Normally, some positive response should be seen after a 4-week strict dietary trial.5
- Textbook of Small Animal Surgery. Douglas H. Slatter
- Digestive Disease in the Dog and Cat. James W. Simpson, Roderick W. Else
- Small Animal Internal Medicine. Richard W. Nelson, C. Guillermo Couto
- Handbook of Small Animal Gastroenterology. Todd R. Tams
- Geriatrics and Gerontology of the Dog and Cat. Johnny D. Hoskins