Caring for Pets with Chronic Diarrhoea

The two most common signs associated with disturbances of the gastrointestinal tract are vomiting and diarrhoea.

If your pet is suffering from the latter and has been for around three weeks, it could be a sign it is chronic as opposed to acute diarrhoea and is because of a food allergy, IBS, parasites, cancer or infections.

The Digestive Tract

For pets to obtain the nourishment they need for their daily life, food must be broken down into smaller nutrients that can be absorbed into the bloodstream. The process of breaking down food particles is called digestion.

This process begins in the stomach and continues in the intestines where the nutrients are absorbed. The liver and pancreas produce substances that aid these processes.

Little of the digestive process occurs in the large intestine. Here, water is reabsorbed into the bloodstream. This is important not only in the production of firm stools but in maintaining the body’s water balance.

Canine Exocrine Pancreatic Insufficiency (EPI)

The pancreas is a V-shaped gland which lies in close proximity to the stomach. The pancreas is important for the production of the hormone insulin (endocrine function) and pancreatic juice (exocrine function).

Pancreatic juice contains enzymes which are important for the digestion of proteins and carbohydrates, but predominantly enzymes which digest fats – called lipases. Some pets (mainly dogs, and occasionally cats) are only able to produce small amounts of pancreatic juice and suffer from a reduced ability to digest nutrients (especially fats).

The undigested fat remains in the small intestine producing diarrhoea. The undigested fat can also be used as a food source for the bacteria in the intestines which can increase in numbers and worsen the severity of the disease. This bacterial overgrowth is a common complication of Exocrine Pancreatic Insufficiency.

Dogs with EPI are often underweight due to impaired nutrient absorption. If fat digestion and absorption are reduced, poor coat condition will result as the essential fatty acids required for coat condition cannot be absorbed.

An essential part of the treatment of the condition is, therefore, to reduce the pet’s dietary fat intake to its lowest possible level and provide a highly digestible diet.

If your veterinary surgeon suspects EPI he may wish to take a blood test to measure the activity of the pancreas.

Management of EPI

Your veterinary surgeon may prescribe pancreatic enzyme replacement medication to help increase digestive capabilities and a special diet to reduce the fat content of the diet.

Some special diets have been specially developed for the management of intestinal disease in dogs with reduced-fat digestibility. These diets also contain supplemented levels of certain nutrients to replace deficiencies commonly associated with this disease.

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a frequent cause of vomiting and diarrhoea, especially in young cats, although vomiting appears to occur more consistently than diarrhoea. Animals with IBD have a severe inflammatory infiltration of the bowel resulting in poor digestion and absorption of nutrients leading to weight loss and poor condition.

The treatment of IBD is based around dietary management and possibly the use of anti-inflammatory medication. Your veterinary surgeon will recommend that you feed a highly digestible so called ‘hypoallergenic’ diet (a diet unlikely to be involved in an allergic response).

These diets usually contain a single meat or fish protein source and a single source of carbohydrate.


Colitis is inflammation of the large intestine (also called the colon) and is characterised by the frequent passage of small amounts of diarrhoeic faeces that may contain blood and/or mucus. Signs of straining and discomfort while attempting to defecate are often seen. Colitis can be caused by many factors including parasites, infections and food allergies or intolerances.

Some pets may have only shown minor signs, whereas others may have a more severe debilitating illness. Some pets are also predisposed to recurrent colitis. Dietary management and anti-inflammatory medication can help to control the inflammation and help to prevent a recurrence.

Anti-inflammatory medication is often required, at least in the early stages of the disease to quickly decrease the inflammation and improve the clinical signs. In certain types of colitis, such as chronic idiopathic colitis, dietary management can reduce the necessity of long-term anti-inflammatory medication.

Dietary Management of Colitis

Chronic idiopathic colitis is one of the commonest causes of chronic diarrhoea in the dog.

In order to reduce the amount of inflammation in the large bowel, your veterinary surgeon may again advise a “hypoallergenic” diet. These diets reduce the number of potentially allergenic materials reaching the colon and therefore minimise allergenic stimulation.

Irritable Colon Syndrome

Some forms of colitis respond to increased levels of fibre in the diet, for example, Irritable Colon Syndrome (a motility disorder, often seen in stressed or excitable dogs).

Fibre is the carbohydrate component of the diet that cannot be digested by the enzymes of the digestive tract and can be described as either:

  • Insoluble fibre (insoluble in water) and
  • Soluble fibre (soluble in water)

Some pets with colitis can benefit from increased levels of both types of fibre in their diet. Inclusion of insoluble fibre returns rates of passage through the bowel to normal, whereas soluble fibre ‘absorbs’ excess water making the stools more solid.

Bacteria present in the colon digest soluble fibre to produce essential fatty acids. These essential fatty acids act as a fuel source for the damaged cells of the wall of the colon helping repair and restoration to health. Your veterinary surgeon may recommend a diet specially formulated to contain increased levels of fibre.

Looking After Pets with Digestive Disorders

Feeding the right diet is the foundation for improving many digestive tract disorders. Everyone who comes into contact with your pet should realise the importance of feeding only the recommended diet; this means avoiding any treats or snacks.

It is also important that your pet is prevented from scavenging food from outside… especially from the rubbish!