Diarrhoea

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Diarrhoea is a common symptom. It may be the result of specific infectious diseases (eg parvovirus), worms and parasites, non-specific bacterial infections, toxins, abnormalities of the gastro-intestinal tract or dietary intolerances. It may occur alone or may also be associated with vomiting.

To understand the causes and associated signs of diarrhoea, it is helpful to give a brief simplified description of your dog’s digestive process. The food is chewed and swallowed where it enters the stomach. This is like a stretchy muscular bag which acts to physically break up the food further and add acid. It then enters a long narrow tube called the small intestine where the body adds special chemicals called enzymes which break down the food to its basic constituent parts. These essential nutrients get absorbed through the wall of the small intestine and all the unwanted material that is left passes onto the large intestine (the colon).

The function of the colon is basically to absorb and conserve water from the bowel contents, thus making the bowel contents solid.  To help the passage of these solids through the bowel the wall of the colon produces mucus as a lubricant and these eventually pass out of the body as faeces.

The severity of signs, the treatment and outlook very much depends on whether it is the small or large intestine that is affected. With small bowel diarrhoea (enteritis) the diarrhoea is very watery and profuse. The body looses a significant amount of fluid, especially if vomiting is also present, making it potentially life threatening. Your dog could become dehydrated, weak and lifeless quite quickly and so professional help is required sooner rather than later. There might be dramatic weight loss.

With large bowel disease, there is not the same degree of fluid loss and so your dog would feel less unwell. However, the irritation of the wall of the colon means the material passes through more quickly so less water is resorbed. More mucus is produced and so the stools tend to be slimy and jellified. The dog squats frequently to pass stools, only passing a little at a time, and trying to go several times in quick succession. The straining commonly causes some bleeding and the condition is commonly associated with flatulence.

Sudden onset large bowel disease will often respond to withholding food for 24hours and then reintroduction of a bland easily digestible food with a gradual return to normal over several days.

Diarrhoea in puppies is especially of concern as they are less able to conserve water and so will dehydrate quickly. The over active motile bowel may result in a condition where the intestine telescopes in on itself resulting in a condition called an intussusceptions. This results in a blockage and needs emergency corrective surgery.

What your veterinarian will want to know

Your veterinarian will want to know how long the problem has been going on, and whether your dog regularly has recurring bouts of diarrhoea. What is his diet? Has this changed? Is your dog fully vaccinated and wormed regularly? Has there been vomiting? Has your dog lost weight?

What your veterinarian may do

Your veterinarian will first assess the level of dehydration and advise whether your dog needs to be hospitalised and given supportive intra-venous fluids. Progress may be monitored by repeated blood sampling. Regular monitoring of puppies is essential to check for the presence of an intussusception. If vomiting is present, it may be important to avoid tablet medication, so giving medications via a drip is very useful.

Stool samples may be analysed to identify the presence of any infective organisms, and also get an idea if any dietary components are undigested.

In the case of colitis, oral medication may be prescribed for home use. However, if there are repeated recurrences, there may be some other problem with the digestion or the diet that is acting as a constant trigger. Your veterinarian may recommend blood tests, ultrasound or even surgical intestinal biopsies to help identify the problem.