Colitis in dogs and cats

The colon plays an important role in the conservation of water and electrolytes and is the major site of faecal storage until expulsion is necessary. With regard to digestion and metabolism, the colon is often underestimated: the colonic bacterial flora plays an important role in the fermentation of undigested carbohydrates, with the primary substrate being dietary fibre. Colitis is defined as inflammation of the colonic mucosa and is the most common cause of large bowel diarrhoea. Inflammation of the colon reduces the amount of water and electrolytes absorbed, and changes colonic motility. Furthermore, the cytokines produced alter smooth muscle function, resulting in abnormal motor activity. Symptomatic treatment (e.g., deworming, rehydration and food adaption) may be sufficient for some cases of acute large bowel diarrhoea; however, it is important to obtain a definitive diagnosis for any animal that has chronic large bowel diarrhoea. The most important causes of large bowel diarrhoea in dogs and cats are colitis, parasites, food-responsive diarrhoea, inflammatory bowel disease, irritable bowel syndrome, fibre-responsive diarrhoea, rectal polyps and neoplasia (e.g., lymphoma and adenocarcinoma). The diagnostic approach to exclude causes of large bowel diarrhoea includes faecal examination, abdominal ultrasound and colonoscopy with biopsies. The blood and urine analyses are normal in most cases. The definitive diagnosis is made by histopathology, where lymphoplasmacytic colitis is found in most cases. Eosinophilic, granulomatous or histiocytic ulcerative colitis are other potential forms of colitis. Depending on the cause of the disease, diet changes, antiparasitics, antibiotics and anti-inflammatory or immunosuppressive therapy are often used.