Colitis in dogs: clinical signs, diagnosis and treatment

What is colitis?

Colitis is inflammation of the colon. The colon is the section of the large intestine that absorbs water, so when it is inflamed, the patient tends to have diarrhoea with a high water content.

Types of colitis in dogs

Colitis in dogs may present in two forms:

• Acute: with a sudden onset and of short duration.

• Chronic: present for at least 2–3 weeks or recurrent.

Causes and signs

In general, the clinical signs of colitis in dogs are an increased frequency of bowel movements of less volume, mucus in the faeces, fresh blood in faeces is also common, but the animal does not usually suffer from vomiting or weight loss, and if there is weight loss, it is due to dehydration (in cases of acute diarrhoea).

Eating disorders are the most common cause of acute colitis in both dogs and cats. Dogs are also suffer from Trichuris vulpis infestations. These disorders may be due to eating too much food, a sudden change between diets, eating rubbish and rotting food, toxins, and hard-to-digest nutrients.

Consequently, depending on each case, the dog presents a clinical picture of osmotic diarrhoea or diarrhoea due to alterations in intestinal permeability. When there is also small intestine involvement (enterocolitis), the diarrhoea may have mixed characteristics.

The most common cause of chronic diarrhoea in dogs is inflammatory bowel disease (IBD). This consists of inflammation of the intestinal mucosa of an unknown aetiology. Besides diarrhoea, IBD also causes vomiting, weight loss and bloody stools.

As inflammatory bowel disease is a disorder of unknown origin, it is diagnosed by ruling out other illnesses, both metabolic and infectious, and its definitive diagnosis is based on an intestinal biopsy to confirm the presence of inflammation. A biopsy is also used to classify IBD into subtypes depending on which inflammatory cells predominate: lymphocytic–plasmatic enteritis, lymphocytic–plasmatic colitis, eosinophilic gastroenteritis, eosinophilic colitis, eosinophilic granuloma, hypereosinophilic syndrome, histiocytic colitis, granulomatous colitis, transmural granulomatous enterocolitis and suppurative colitis.

Management of colitis in dogs: diagnosis and treatment

The management depends on whether it is acute or chronic colitis.

Acute colitis usually resolves spontaneously, that is, it is self-limiting.Which is why we don’t usually make an aetiological diagnosis.

As in all cases, start with a thorough anamnesis and physical examination. It is important to detect any signs of alarm (poor general condition, bloody diarrhoea, frequent vomiting) or, by contrast, an absence of warning signs (good overall health, no localised disease, inappropriate diet, only mild vomiting), as this will determine which complementary tests and treatments should be implemented. If there are no signs of alarm, a blood test for haematocrit, protein and PCV/TS (packed cell volume/total solids) is sufficient to check whether there is dehydration. A more extensive analysis (blood count, biochemistry tests) is necessary for the most severe cases including imaging tests such as ultrasound and X-rays, bile acid tests and a stool culture (for more information on diagnostic tests you can read this post).

In general, treatment is symptomatic, involving fluid replacement (oral or intravenous if there are signs of alarm or dehydration) and the abstinence of solid foods for 24–48 hours. One option is the administration of [loperamide] to reduce the frequency of movements, but this should not be given if a toxin-induced picture is suspected.

Normal bowel movements are restored within 2–5 days, and it is advisable to offer highly digestible foods when solids are resumed such as low-fat diets with easily digested carbohydrates and high-biological value proteins.  Once acute diarrhoea has been excluded from the diagnosis following 2–4 weeks of standard treatment, it is worth spending the time and money to obtain a specific diagnosis to guide management of the problem.

The prognosis is excellent, but some semi-wild animals have frequent relapses due to their habit of eating rubbish.

Chronic colitis is more complicated and does not resolve without intervention. A protocol must be followed to progressively rule out possible causes. Therefore, the following should be eliminated: parasites, bacterial infection, systemic diseases (renal, hepatic, pancreatic), diffuse lymphoma, neoplasms, lymphangiectasia and fibre-responsive colitis (AVD Diabetes Colitis). Once these have been ruled out, there are two options: empirical treatment or an intestinal biopsy, which may be normal or present signs of mild or severe inflammation.

Chronic colitis typically requires a special high-fibre hypoallergenic diet, as well as immunosuppressants, probiotics, etc. Antibiotic therapy may be applicable in some cases.

There are three main diseases involving chronic diarrhoea:

• Antibiotic-responsive diarrhoea, which improves with antibiotics (to learn more about when antibiotics are indicated for diarrhoea, click here) and a specific diet.
• ​A food allergy, which will improve with a hypoallergenic exclusion diet.
• Inflammatory bowel disease (IBD), where the biopsy will show signs of inflammation and which will improve with a specific diet and immunosuppressants.

The most common chronic enteropathies respond to diet, followed by those which respond to antibiotics and lastly are inflammatory conditions.

It is therefore important to carry out exclusion diet tests and administer antibiotics to determine the origin of the enteritis, as histopathological results do not differentiate between the various chronic enteropathies.                       

At Affinity we recommend the special diet for colitis which you can find here.

In our blog you will also find various posts about diets and nutritional supplements for the treatment of diarrhoea.