What causes diarrhea in dogs and cats?

Diarrhea in dogs and cats can be caused by stress, viruses, bacteria, parasites, foreign bodies (including bones, sticks, and other objects), diet, food allergies, toxins, tumors, disease, and more. Your ability to answer questions about your pet’s diet, habits, environment, and specific details about the diarrhea can help the veterinarian narrow the list of possible causes and to plan for specific tests to determine the cause.

Diseases outside the intestinal tract that may cause diarrhea include kidney failure, liver failure, pancreatic disease, and, in cats, hyperthyroidism. Severe inflammation of the pancreas (pancreatitis) can lead to damage of the pancreas and an inability to make enough enzymes to digest fat. This is called pancreatic insufficiency and causes diarrhea with a large volume of greasy stool. Pancreatic insufficiency can occur in young animals due to a congenital deficiency of pancreatic enzymes.

Small intestinal and large intestinal diarrhea have different causes, require different tests to diagnose, and are treated differently.

What are the symptoms of small intestinal diarrhea?

Small intestinal diarrhea results in a larger amount of stool passed with a mild increase in frequency, or about 3 to 5 bowel movements per day. The pet doesn’t strain or have difficulty passing stool. Animals with small intestinal disease may also vomit and lose weight. Excess gas production is sometimes seen, and you may hear the rumbling of gas in the belly. If there is blood in the stool, it is digested and black in color.

Dogs and cats with chronic small intestinal diarrhea will lose weight as they are unable to properly absorb nutrients and may develop edema of the legs or fluid accumulation in the belly or chest. A small protein, albumin, may be lost in diarrhea. Albumin acts like a sponge to keep water in the blood vessels. When albumin is lost in the stool, blood albumin gets low, and water leaks out of blood vessels to accumulate in other locations.

Chronic diarrhea may cause the fur to look dull and brittle due to nutrient deficiencies.

What causes small intestinal diarrhea?

A sudden onset of small intestinal diarrhea may be caused by viruses like canine distemper, canine parvovirus, canine coronavirus, feline panleukopenia virus, and feline coronavirus, in young, poorly vaccinated pets. It can also be caused by bacteria such as salmonella, clostridia, or campylobacter.

What are the symptoms of large intestinal diarrhea?

Disease of the large intestine, including the colon and rectum, cause the pet to pass small amounts of loose stool often, usually more than 5 times daily. The pet strains to pass stool. If there is blood in the stool, it is red in color. The stool may be slimy with mucus. The pet does not usually vomit or lose weight with large bowel diarrhea.

What are some of the causes of large intestinal diarrhea?

Worms and giardia can cause small intestinal diarrhea, mostly in young animals. Foreign bodies, including bones, sticks, and other objects, can pass through the stomach and get stuck in the intestine, causing both diarrhea and vomiting. These same foreign materials may pass through the intestinal tract without getting stuck but may damage the lining of the intestinal tract and cause diarrhea. Dietary indiscretion or a sudden change in diet can cause diarrhea with or without vomiting. Food allergies in dogs and cats can cause diarrhea, vomiting, or itchy skin. Toxins, including lead and insecticides, can cause diarrhea, usually with vomiting.

Inflammatory bowel disease (IBD) occurs commonly in both dogs and cats and is another potential cause. In IBD, the walls of the intestine contain abnormal numbers of inflammatory cells. The cause of IBD is not known but is suspected to be an allergic reaction to components of food, bacteria, or parasites.

How do you determine what is causing diarrhea?

The cause of small intestinal diarrhea may be determined from blood tests, examination of the stool, X-rays, or ultrasound of the abdomen or by endoscopy. Small biopsies of the lining of the intestine can be taken for microscopic evaluation.

The diagnosis of large intestinal diarrhea is also made by blood tests and examination of the stool. A rectal examination using a gloved finger may provide some information about the cause of large bowel problems including rectal polyps and rectal cancer. Endoscopy to examine the large intestine is performed using a rigid or flexible scope passed up the rectum. Because the rectum is often very irritated, colon exams are usually performed under general anesthesia.

How do you treat diarrhea in cats and dogs?

The treatment of animals with diarrhea can vary significantly depending on the cause.

Often, acute small intestinal diarrhea can be managed by withholding food, but not water, for 24 – 48 hours. If diarrhea stops, small amounts of a bland low-fat food can be fed 3 to 6 times daily for a few days, with a gradual increase in the amount fed and a gradual transition to the pet’s normal diet. Foods designed as intestinal diets usually contain rice as rice is more digestible than other grains.

You should not administer over-the-counter diarrhea medications without consulting a veterinarian.

Diarrhea that continues for more than a few days or is accompanied by depression or other signs is an indication to take your pet to a veterinarian.

The treatment of large bowel diarrhea may be based on a specific diagnosis. Non-specific treatment of large bowel diarrhea often includes a high fiber diet and sulfasalazine, an anti-inflammatory drug.

What should I do if my dog or cat has diarrhea?

If your pet has diarrhea, you should consult with your veterinarian or call the WSU Veterinary Teaching Hospital at 509-335-0711.