Chronic (Long Term) Diarrhea in Cats

At a glance

  • About: Chronic diarrhea is the passage of loose, watery stools which may be more or less frequent than usual. Diarrhea can decrease the number of nutrients your cat needs as well as cause dehydration due to loss of fluids in the feces. It is essential to seek veterinary attention for a cat who has had diarrhea lasting longer than 2-3 days or is accompanied by other symptoms.
  • Causes: Parasites, gastrointestinal disease, systemic disease, dietary, chronic infections.
  • Diagnosis: Baseline tests, imaging, and specific tests depending on the suspected cause.
  • Treatment: The goal of treatment is to address the underlying cause and provide supportive care such as fluids and nutrition.



  • Food allergy: The third most common type of allergy in cats (behind flea allergy and inhalant allergy). The most common causes of food allergies are fish, beef, chicken, eggs, and wheat.
  • Food intolerance: Occurs when the body has a reaction to eating a particular food or drink such as milk.

Chronic infections

Cats most vulnerable to chronic infection are senior cats, kittens under six months, cats with a compromised immune system, stressed cats and cats in an overcrowded environment.

  • Bacterial infection: Salmonellosis, campylobacteriosis, E. coli, tuberculosis, tularaemia.
  • Viral infection: Feline immunodeficiency virus, feline leukemia virus, and rotavirus.
  • Protozoa infection: Trichomonosis, giardiasis or cryptosporidiosis.
  • Parasitic infection: Liver flukes, parasitic worms such as roundworm and hookworm.
  • Histoplasmosis (disseminated): A rare fungal infection that usually affects the lungs, in some cases, the infection can spread throughout the body, causing several symptoms including diarrhea.


  • Hyperthyroidism: A benign hormone-secreting tumour of the thyroid gland.
  • Kidney disease: Chronic which is slow and progressive and seen most often in middle-aged to senior cats or acute, which is sudden onset.
  • Liver disease: This may be due to ingestion of toxins, congenital disorders, infection or inflammation.
  • Cancer: Lymphoma is a cancer of the lymphoid tissue. It can develop in many parts of the body, but it affects the gastrointestinal tract most often.
  • Exocrine pancreatic insufficiency: Also known as maldigestion disorder, exocrine pancreatic insufficiency (EPI) is a disease caused by a failure of the pancreas to secrete adequate levels of pancreatic enzymes which results in an inability to digest food properly.


  • Inflammatory bowel disease: A poorly understood group of conditions in which different types of inflammatory cells invade gastrointestinal mucosa.
  • Pancreatitis: Inflammation of the pancreas which has several underlying causes.


  • Lead poisoning: Lead poisoning (plumbism) can be acute or chronic, depending on the level and type of exposure. Chronic lead poisoning can occur in cats who are exposed to lead paint dust during renovations of older homes or if the cat eats or drinks from a bowl that contains lead.
  • Gastrointestinal obstruction: A partial gastrointestinal blockage refers to the blockage anywhere from the stomach (gastro) to the intestines. Blockages can develop anywhere in the small or large intestine; it may be partial or complete. Causes include an ingested foreign object, hairballs, tumours, heavy worm infection, twisting of the intestine, telescoping of the intestine and adhesions.


A healthy cat stool should be well-formed, firm, but not too dry, and chocolate brown in colour. The most obvious sign of diarrhea is loose, watery stools. There are differences between diarrhea that have originated from the small intestine or the large intestine.

  • Small intestine diarrhea: Volume is increased, frequency 2-3 times normal, no mucus, urgency may be normal to mildly increased. Cats with chronic small intestinal diarrhea lose weight and body condition as they are not absorbing nutrients.
  • Large intestine diarrhea: Volume is normal to decreased, mucus and blood may be present, the urgency is increased, and frequency is more than five times normal.

Other symptoms depend on the underlying cause but may include:

  • Vomiting
  • Weight loss
  • Dehydration
  • Pain when defecating
  • Defecating outside the litter tray
  • Increased or decreased appetite
  • Increased thirst
  • Foul-smelling feces
  • Frothy or greasy feces
  • Blood in the feces
  • Mucus in the feces

How to determine which cat has diarrhea in a multi-cat household:

If you have more than one cat and don’t know which one has diarrhea, buy a box of crayons (Crayola are non-toxic if ingested), and grate different coloured crayons. Add a small amount of each colour to your cat’s food. It will be necessary to feed the cats separately; each cat has its colour. So, one cat has yellow crayon mixed into its food; the next cat has red crayon mixed into its food. The crayon will safely pass out of the cat’s body via the feces.


The veterinarian will perform a complete physical examination of the cat and obtain a medical history from you. The age of the cat, as well as medical history and any accompanying symptoms, may give the veterinarian a clue as to the underlying cause. A young cat is more likely to have an infection, hyperthyroidism, cancer and chronic kidney disease are typically diseases of middle-aged to older cats.

Diagnostic workup:

Baseline tests: Biochemical profile, complete blood count and urinalysis to evaluate the overall health of the cat, including liver and kidney function and concentration of the urine which will may reveal dehydration which is common in cats with chronic diarrhea and kidney disease.

Fecal tests: Flotation, direct smear, antigen, swab, and cytology to look for the presence of parasites, giardia cysts and bacteria in the feces.

Acid-fast stain: Stool samples are sent to a specialist laboratory for testing in cats suspected of having cryptosporidium. The oocysts of Cryptosporidium are detected with the acid-fast stain technique, which stains the oocysts red. To increase the chance of an accurate diagnosis, several stool samples may be required.

Snap test: IDEXX Laboratories have a SNAP Giardia test kit which is available for in-house testing. The sensitivity of this test is 90%.

Biopsy/histopathology: To evaluate for inflammatory bowel disease or cancer.

T3 and T4 Tests: These blood tests measure levels of T3 and T4 hormones, which are secreted by the thyroid gland, elevated levels occur in cats with hyperthyroidism.

Food elimination trial: If a food allergy is suspected, the cat will be placed on a food elimination trial which usually lasts between 8-12 weeks. During this time, you must not give your cat any other foods, treats, vitamins, minerals or chewable medications apart from the prescribed diet. If any other foods or vitamins are provided during this trial, it will invalidate the results. If the allergy clears up after the specified time, then a food allergy is the likely cause. The diet given to your cat during the trial will be food the cat has never had before such as rabbit, duck or venison. The diet can be homemade or a special prescription diet which is only available from your veterinarian.

Imaging: Xrays and ultrasound can be a useful diagnostic tool to evaluate the gastrointestinal tract and internal organs for signs of abnormality and to look for tumours or blockages.

Endoscopy: A flexible plastic tube with a light and a camera at the end is used to evaluate the gastrointestinal tract.

Blood tests: If the veterinarian suspects lead poisoning, a blood test will be necessary to check levels of lead in the blood.

Barium studies: A barium study is a diagnostic test to evaluate suspected gastrointestinal disease. Barium sulfate is administered to the cat via syringe into the cheek pouch. Once swallowed, the barium coats the inside walls of the gastrointestinal tract which shows up the structures as bright white on x-rays.

ELISA (enzyme-linked immunosorbent assay): This test can detect the antigens to specific pathogens such as FeLV, FIV, giardia, and cryptosporidium.

fTLI (feline Trypsin-Like Immunoreactivity): To measure the concentration of trypsin-like proteins in serum. Elevated levels may be indicative of pancreatitis.

fPLI (feline Pancreatic Lipase Immunoreactivity): To measure feline pancreatic lipase (an enzyme secreted by the pancreas which breaks down fat) immunoreactivity in serum.

Fecal proteolytic activity: Examination of the feces for fecal fat and fecal trypsin for cats with suspected exocrine pancreatic insufficiency.


Treatment can vary depending on the underlying cause of diarrhea. Once that is addressed, diarrhea should resolve.

Bacterial or protozoal infection: Antibiotics and supportive care while the cat recovers.

Protozoal infection: Fenbendazole is an anti-worming medication and metronidazole is an antibiotic that can be used to treat giardia. Ronidazole is an antibiotic and antiprotozoal which can be used to treat tritrichomonas. There are no drugs approved for treatment for Cryptosporidium and treatment is supportive.

Viral infection: Where available, such as cats with FIV or FeLV, anti-viral medications to control the virus and supportive care. Cats with FIV and FeLV often have a compromised immune system, so care must be taken to avoid opportunistic infections. This may include keeping the cat indoors, in a stress-free environment, diligent parasite control, feeding a good quality diet and a possible change in vaccination schedule.

Food allergy or intolerance: For cats who have food allergies, feed a hypoallergenic or homemade diet. Where possible, avoid the food which caused the intolerance.

Inflammatory bowel disease: Cats with IBD can benefit from a highly digestible, low fat, novel protein diet. Other treatments include corticosteroids to control inflammation, antibiotics, immunosuppressive drugs, and where available, fecal transplant, which is an evolving therapy.

Kidney disease: Switch to a low-protein diet, phosphorous binders and manage symptoms such as nausea and dehydration.

Liver disease: Find and treat the underlying cause where possible, feed a low-fat, low-protein diet.

Hyperthyroidism: There are several available treatments for cats with hyperthyroidism. It is possible to cure the disease with surgery or radioactive iodine, which kills the tumour while sparing the healthy thyroid tissue. Hills y/d is a diet that is low in iodine and can manage but not cure the condition.

Pancreatitis: Where possible, treat the underlying cause. Supportive care to relieve symptoms and can include painkillers, anti-nausea medication, a bland diet, or for cats who are not eating, a feeding tube.

Exocrine pancreatic insufficiency: Powdered pancreatic extracts (from cow and pig pancreases) with each meal to assist with the digestive process. This treatment has a good outcome, but it is a lifelong treatment and is expensive.

Histoplasmosis: Mild cases of histoplasmosis may not require any treatment. Itraconazole or ketoconazole are common drugs to kill the infection. The cat remains on medication for between 4-6 months and occasionally as long as 12 months.

Lymphoma: The mainstay of treatment for lymphosarcoma in cats is chemotherapy. Cats tolerate chemotherapy well, although some can may experience effects such as anorexia or lethargy. Lymphosarcomas tend to respond well to chemotherapy, but this treatment is not curative, it can, however, give your cat some extra time.

Partial gastrointestinal obstruction: Most cases of gastrointestinal obstruction require surgery. That includes tumours, hernias, twisted or telescoped intestines, and pyloric stenosis.

Lead poisoning: Chelation therapy binds to lead in the blood and is excreted out in the urine.

Treatment of chronic diarrhea may include the following:

Fluids: To treat dehydration and correct electrolyte imbalances.

Tylosin: A broad-spectrum antibiotic may be prescribed for its anti-bacterial and anti-inflammatory properties.

Nutritional support: Encouraging the cat to eat by offering palatable food or warming it slightly, or in cats who are not eating, a feeding tube may be necessary.

Probiotics: Can help to replace helpful gut flora.


  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio