Chronic diarrhoea in dogs and cats

What is chronic diarrhoea?

Chronic refers to a disease that has been ongoing, either persistently or intermittently for three weeks or more. Whereas diarrhoea, as many of us can relate, is the passing of soft or loose stool. This stool is usually soft enough that it needs to be scraped up rather than picked up. It can range from the consistency of thick porridge to watery like soup.

What causes diarrhoea?

Diarrhoea occurs when the food and liquids consumed undergo an increased rate of passage in the gut, leading to poor absorption of nutrients, electrolytes and water. This leads to the expulsion of only partially digested, watery stool

There are many causes of diarrhoea and they can be simple to complex. Infectious causes such as parasites, viruses and bacteria are often to blame. Some animals have a more sensitive digestive system that tends to revolt whenever they eat something unusual, whether it is something they have stolen out of the garbage or from your plate. Even sudden changes in diets such as changing a food brand can cause a reaction.

Autoimmune diseases due to an overactive immune system or even allergies can cause a problem too. Other causes of diarrhoea include systemic illness (liver disease or thyroid disorders) or even from medications that can have diarrhoea as a side effect.

Diarrhoea is often categorised into three groups: small bowel (affecting the small intestine), large bowel (affecting the large intestine) or mixed. The classification depends on the characteristics of the diarrhoea.

Causes of small bowel diarrhoea:

parasites (hookworms, roundworms and Giardia)
pancreatic disease
inflammation of the liver and biliary system, the pancreas and the intestine also known as triaditis
inflammatory bowel disease (IBD)
feline hypothyroidism
feline leukaemia virus and feline immunodeficiency virus (feline AIDs)
fungal enteritis (Histoplasmosis)
cancer; alimentary lymphosarcoma
bacterial overgrowth, dysbiosis and enterotoxicosis

Causes of large bowel diarrhoea:

parasites (whipworms, trichomonas and Giardia)
irritable bowel syndrome (IBS)
inflammatory bowel disease (IBD)
immune mediated disease (plasmacytic lymphocytic colitis, histiocytic ulcerative colitis) and eosinophilic colitis
allergies and food sensitivities

When will I know if my pet’s diarrhoea is a problem?

A bout of the squirts is not usually a problem if it is short lived and resolves on its own. This occurs in most cases. However, when animals have a more serious underlying cause, or are very young, diarrhoea can turn serious pretty quickly.

Any case of diarrhoea that does not resolve on its own after a few days is considered a problem that should be addressed. This is even if your pet is still lively and eating well. Pets with chronic diarrhoea lose important nutrients and electrolytes, which leads to their own long term consequences.

The most important thing to consider with diarrhoea is dehydration, which in young and old animals can happen quickly with fatal results. If they also have other symptoms, such as vomiting, then they can lose water a lot faster.

It is important to keep an eye out for other symptoms aside from the diarrhoea, such as vomiting, poor appetite, are more tired than usual or any other changes in behaviour. Be sure to mention these to the vet.

What should I do if my pet has chronic diarrhoea?

If your pet has diarrhoea that has been ongoing for some time without resolving, or even if it waxes and wanes but never really stays away, it would be wise to consult the veterinarian. We will often ask you to bring along a fresh stool sample to your appointment.

What will the vet do if my pet has chronic diarrhoea?

The first thing the vet will do is to perform a thorough physical exam on your pet. This is to check if they have a fever, are dehydrated, see if they have any pain in their belly or show any other symptoms that can be used to build a more complete picture. The vet will gather as much information as possible to treat the cause of the problem, rather than just the symptoms.

They will require as much history on your pet’s condition as you can give.

Questions sure to be asked include:

How long has the condition been going on?
Has the problem been persistent or intermittent?
When did you first notice the diarrhoea?
Did your pet eat or do anything out of the ordinary shortly before the diarrhoea began?
Were there any recent changes in diet or environment, recent travels or sources of stress?
Are there new family members or pets at home, or has a family member or pet recently passed away?
Is your pet on any medication, or have they had access (intentional or not) to any medications at home, cleaning materials, chemicals, toxins or even household plants?

Characterising the diarrhoea will also be very important as this will allow the vet to narrow down where the diarrhoea is coming from, and whether it’s in the small or the large intestine. This is important as treatment will differ depending on the cause and location of the problem.

Characterising the diarrhoea will look at characteristics such as how often your pet needs to go and if there is any urgency; if they strain when they squirt; if there is any blood or mucous in the stool as well as its colour and smell.

Diarrhoea that originates from the small intestine generally shows an increased volume of faeces, but the frequency is about the same, sometimes increased. They don’t generally show a real urge to go, but additional gas and sometimes a fatty consistency is seen. If blood is included, this is usually very dark, almost black in colour, rather than bright red. Because the job of the small intestine is primarily nutrient absorption and digestion, pets with chronic small intestinal diarrhoea tend to lose weight over time. These animals may also be nauseated or vomit.

Pets with large intestinal diarrhoea tend to have small deposits more frequently, often straining, are urgent for a deposit and appear uncomfortable. These animals may have a more mucoid diarrhoea with mucosal irritation. If blood is present, it is often seen as bright red rather than dark or black.

Can the vet test for the cause of the diarrhoea?

There are many tests available depending on what the vet is looking for. They will narrow down the list of suspects based on the character of the problem as well as any other symptoms seen. Usually they will start with some simple tests in order to gather more information before testing for a specific culprit.

The best place to start is generally the stool itself. The vet will analyse a sample by checking for parasites as this is one of the most common causes of diarrhoea in pets. This may include a faecal float to look for worm eggs, a faecal wet prep to search for parasites and in some cases, a stain will be made of the sample and checked under the microscope. If there is pain in your pet’s belly or if the vet can feel a bump or mass where there shouldn’t be one, they will likely recommend an x-ray or even an ultrasound scan of your pet’s belly.

Other testing that can be done includes blood tests, which look at the level of dehydration, levels of blood proteins (which can indicate autoimmune disease) and even blood loss through the gut. In older cats with chronic diarrhoea, testing their thyroid levels may be advised. Blood tests can also be used to test the function of the pancreas and liver, which may also play a role in chronic diarrhoea. Some viruses that can cause diarrhoea in puppies such as parvo and coronavirus, as well as feline leukaemia virus or feline AIDs virus in cats, can be tested within minutes with blood or stool samples.

When something abnormal is found at this base level, the vet may recommend biopsies or cultures depending on what they are looking for. These are sent to the lab and are usually focused on specific parasites or bacteria in the case of cultures, or specific autoimmune diseases for biopsies.

How can chronic diarrhoea be treated?

The treatment will depend on the cause. In most cases the vet will recommend a dewormer, even if no parasite eggs were found. The majority of diarrhoea cases respond very well to the use of a bland diet at home. The best would be a veterinary diet, which consists of highly digestible proteins and carbohydrates with low fats. These diets include increased omega oils to reduce inflammation and special prebiotic fibres to slow the transit time in the gut and promote the growth of good bacteria. Good old boiled chicken and rice work fairly well but obviously don’t have all the extras of a prescription diet. The vet will likely include a probiotic to quickly replace the good bugs that often get knocked out with gastrointestinal disease.

Infectious conditions may require antibiotics to treat, while autoimmune diseases will require immune suppressants. Cases of significant dehydration may require a drip and hospitalisation as their best course of action.

Irrespective of the cause, treatment will be tailored to each patient individually. Everyone is different and treatment will be adjusted based on test results and individual response to treatment.