Cat Diarrhea: Causes and Solutions Explained by a Veterinarian

While you are raising a cat, it is likely that they will have diarrhea at least once. When that happens, what should a pet owner do?

There are a great many causes for diarrhea in cats. While you will likely take your cat to a veterinary clinic if they have diarrhea, it is no exaggeration to say that the information provided by the owner can influence the treatment. Observe the condition of the stool carefully without panicking. In this article, we will explain the causes of and how to deal with diarrhea in cats.

The Difference Between Normal Cat Stool and Diarrhea

You might have an image of cat stool as being firm, round, and containing little moisture. By veterinary definition, stool is considered normal when it is about 70% water, while 80% or more is considered diarrhea.

Let's learn the difference between normal stool and diarrhea.

Normal Stool

A cat's normal stool is well-formed with visible cracks on the surface. The surface may be slightly moist, but it will not lose its shape even if you pick it up.

Diarrhea

Diarrhea is defined as anything ranging from unformed stool (soft stool) to completely liquid stool (liquid, watery, or muddy stool).

Soft stool is very soft. Its characteristic is that it falls apart when you try to pick it up.

Liquid stool refers to a state where it is almost entirely fluid.

Causes of Diarrhea in Cats

There are many causes for diarrhea in cats. The primary causes are stress, diet, and disease, but most cases of diarrhea are due to disease.

Stress

Environmental changes (moving, changing seasons, guests, etc.) can cause temporary stress. This leads to a decrease in immunity and an imbalance in intestinal bacteria, making diarrhea more likely to occur.

Diet

If diarrhea occurs when switching to food containing specific ingredients, it may be a food allergy. Additionally, food that has been sitting for a long time after opening has degraded and can cause diarrhea.

Cats cannot break down the lactose found in cow's milk meant for humans. Feeding them human milk will also cause diarrhea.

Disease

There are many diseases that cause diarrhea. Here are the main diseases that lead to diarrhea.

・Parasites

Parasites that live in a cat's intestines, such as roundworms and tapeworms, as well as protozoa like Giardia, Tritrichomonas, and Coccidia, cause diarrhea. Some are visible, while others can only be seen with a microscope.

・Viruses

Viral diarrhea can be fatal for kittens.

Feline parvovirus requires particular attention; infection has a very high mortality rate. Furthermore, this virus is highly infectious, meaning it can spread to other cats in the home unless proper disinfection is performed.

Feline coronavirus is another virus that causes diarrhea, often resulting in mild diarrhea in kittens. This virus is also the cause of FIP, which is mentioned below.

・Chronic Kidney Disease

Cats almost always develop chronic kidney disease once they reach their senior years. One of the symptoms of chronic kidney disease is diarrhea.

In chronic kidney disease, the body's ability to excrete water through urine declines. As a result, the body cannot properly regulate the water content in the stool, leading to diarrhea.

・Immunodeficiency

When cats have FIV or FeLV, their overall immunity drops significantly, which can lead to an overgrowth of pathogenic bacteria in the intestines and cause diarrhea. Additionally, cats with immunodeficiency often have a decreased appetite due to severe stomatitis, which can cause abnormal intestinal movement and lead to diarrhea.

・Neoplastic Disease

Among neoplastic diseases in cats, those that occur in the abdomen can cause diarrhea. When inflammation becomes severe due to a tumor, it spreads to the intestinal tract, causing the intestines to swell (edema). Because the swollen intestines contain a lot of water, moisture easily enters the stool, and the inflammation causes abnormal intestinal motility, leading to diarrhea.

・FIP (Feline Infectious Peritonitis)

FIP occurs when the aforementioned feline coronavirus, which causes mild diarrhea, undergoes a mutation in the cat's intestines. FIP types include the "wet" type with fluid buildup in the abdomen or chest, the "dry" type that forms granulomas (masses) in the body, and a mixed type showing both. Since it is caused by a virus that originally triggers diarrhea, diarrhea is one of the symptoms. Treatment for this disease has not yet been established, so most cats pass away before a diagnosis can be confirmed.

How to Treat Cat Diarrhea

If your cat has diarrhea and it resolves after one instance, it might be okay to observe them for a little while. However, if they have persistent diarrhea, there is a risk of dehydration, so take action early.

Visit a Veterinary Clinic

If your cat has diarrhea, we highly recommend visiting a veterinary clinic first. Most cases of diarrhea are due to disease, and there is a possibility of infectious diseases that can be passed to other animals or humans. Also, when visiting the vet, be sure to bring a stool sample. The sample should be as fresh as possible.

Additionally, keep a record of the frequency of bowel movements, presence of other symptoms, type of food, and vaccination/parasite prevention history to share with your veterinarian.

Review Their Diet

If the food you are using has been open for a long time, discard it immediately. Dry food should be used within one month of opening, and wet food should be used within two days if kept refrigerated after opening.

If you are feeding them cow's milk, switch to milk specifically for cats.

If diarrhea occurs with food containing specific ingredients, there may be a food allergy, so switch to a completely different food. However, as allergic reactions do not subside immediately, they may continue to have diarrhea for a while even after switching food. Continue the new diet for two weeks and monitor the stool. If it gets worse, consult your veterinarian.

Since diagnosing an allergy is difficult through diet changes alone, always see a veterinarian.

Consider Stress

Cats can develop diarrhea due to environmental changes. While it is difficult to manage diarrhea caused by changing seasons, in cases like moving or guests, allow the cat to stay in a quiet place until they feel calm. Diarrhea caused by stress is transient. It can likely be alleviated with supplements such as probiotics.

Summary

If the diarrhea resolves quickly, it is generally fine to monitor your cat. However, if the diarrhea is prolonged or happens multiple times a day, your cat could become dehydrated or, in the case of progressive diseases, the condition could worsen. Furthermore, diarrhea caused by pathogens carries the risk of infecting other animals or humans.

Observe the frequency and condition of your cat's stool daily, and consult a veterinary clinic if there is even the slightest abnormality.

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