Diarrhea in Cats: Causes, Diagnosis and Treatment

What is diarrhea?
Diarrhea is the rapid movement of ingested material through the intestine, resulting in one or more of the following: increased frequency of bowel movements, loose stools, or increased amount of stool.

If my cat has diarrhea, when should I call my veterinarian?
If your cat has diarrhea, call your veterinarian. Your veterinarian will ask you a series of questions to determine how severe the diarrhea is. It will be helpful for your veterinarian to know when the diarrhea started, how many bowel movements your cat has had, what they look like, and if your cat is uncomfortable. It is especially important that you call your veterinarian immediately if your cat:

Has blood in the diarrhea or the stools are black or tarry
You suspect your cat may have eaten something toxic or poisonous
Your cat has a fever, is depressed, or dehydrated
Your cat's gums are pale or yellow
Your cat is a kitten or has not received all his vaccinations
Your cat appears to be in pain
Your cat is also vomiting

Do not give your cat any medications, including over-the-counter human medications unless advised by your veterinarian to do so.

How is the cause of diarrhea diagnosed?
There are many causes of diarrhea (See Table 2. Causes, Diagnosis and Treatment of Diarrhea in Cats). It is important to determine the cause so the appropriate treatment can be given. Your veterinarian will combine information from you, the physical exam, and possibly laboratory and other diagnostic tests to determine the cause of the diarrhea.

Localization of symptoms - Since there are so many causes of diarrhea, it first helps to determine which part of the intestine is most likely involved. By localizing the diarrhea to the small or large intestine, the number of possible causes can be narrowed down. To do this, your veterinarian will need information related to what particular symptoms are occurring, as shown in Table 1.

Table 1. Symptoms of diarrhea due to a small intestine disease versus a large intestine disease

Symptom Small Intestine Diarrhea Large Intestine Diarrhea

Volume of stool Increased Normal or slightly increased or decreased

Frequency of bowel movements Normal to increased Usually very increased

Straining Uncommon Common

Blood present Uncommon; digested blood may result in black, tarry stools Common; fresh red blood is seen

Mucous present No Large amount common

Weight loss Common Uncommon

Vomiting Possible Uncommon

Increased gas Possible Uncommon

Onset of symptoms - How suddenly the symptoms appeared is also a good clue to what the cause of the diarrhea may be. If the symptoms appeared suddenly, the condition is called "acute". If the symptoms remain over a long period of time (weeks), the diarrhea is called "chronic". If the symptoms appear, go away, and then come back again over several weeks, the diarrhea is considered "intermittent."

Medical History - Your veterinarian will ask about your cat's medical history including vaccinations, what type of wormer the cat has received and how often, contact with other animals (including wildlife), diet, any access to garbage or toxins, and any medications. The more information you can offer, the easier it will be to make a diagnosis.

Physical examination - Your veterinarian will do a complete physical exam including taking your cat's temperature, checking the heart and respiration, looking in the mouth, palpating the abdomen, and checking for dehydration.

Laboratory and diagnostic tests - In almost all cases of diarrhea, your veterinarian will recommend a fecal flotation. This is a test to check for parasites such as worms or Giardia. If a bacterial infection is suspected, a fecal culture and sensitivity are performed.

If the cat is showing signs of illness, a complete blood count and chemistry panel are often recommended. Usually blood tests to check for the presence of feline leukemia virus (FeLV) to and feline immunodeficiency virus (FIV) are also recommended. Other special blood tests may also be conducted if certain diseases are suspected.

Radiographs (x-rays) are appropriate if a tumor, foreign body, or anatomical problem is suspected. Other diagnostic imaging such as a barium series or ultrasound may also be helpful. Examinations using an endoscope or colonoscopy may be indicated.

For some diseases, the only way to make an accurate diagnosis is to obtain a biopsy and have it examined microscopically.

How is diarrhea treated?
Because there are so many causes of diarrhea, the treatment will vary (See Table 2. Causes, Diagnosis and Treatment of Diarrhea in Cats).

In many cases of simple diarrhea in adult cats, it is recommended to withhold food for 12-24 hours, and provide small amounts of water frequently. Then, a bland diet such as boiled (fat-free) chicken and rice is offered in small amounts. If the diarrhea does not recur, the cat is slowly switched back to his normal diet over the course of several days.

For some cases of diarrhea, it may be necessary to modify the diet permanently. Special foods may need to be given as a way to avoid certain ingredients, add fiber to the diet, decrease the fat intake, or increase digestibility.

If parasites are present, the appropriate wormer and/or other medication will be prescribed. Few wormers kill every kind of parasite, so it is very important that the appropriate wormer be selected. In most cases it is necessary to repeat the wormer one or more times over several weeks or months. It is also important to try to remove the worm eggs from the environment. The fecal flotation test looks for worm eggs, and if no eggs are being produced, the test could be negative even though worms could be present. For this reason, in some cases, even if the fecal flotation test is negative, a wormer may still be prescribed.

If dehydration is present, it is usually necessary to give the cat intravenous or subcutaneous fluids. Oral fluids are often not adequate since they pass through the animal too quickly to be absorbed properly.

Antibiotics are given if the diarrhea is caused by bacteria. They may also be given if the intestine has been damaged (eg., blood in the stool would indicate an injured intestine) and there is a chance that the injury could allow bacteria from the intestine into the blood stream, possibly causing severe disease (septicemia).

In some cases, medications may be given to decrease motility, ie., slow down the rate at which the intestine moves ingested material through. These drugs should not be given if the cat could have ingested a toxin or may have a bacterial infection, so it is always important to have an accurate diagnosis before use of these drugs.

Table 2. Causes, diagnosis and treatment of diarrhea

Cause Example Cats Most at Risk Symptoms Diagnosis Treatment Prognosis

Diet change Changing cat food brand or feeding a high fat meal Those switching from a consistent diet Usually no other signs of being ill History and physical exam; tests (eg., fecal flotation) to rule out other causes Withhold food then switch to bland diet and then slowly back to normal diet Excellent

Food intolerance or sensitivity Sensitivity to or inability to digest or absorb certain foods such as milk Sudden onset of diarrhea, sometimes with gas Response to removing ingredient from diet and then adding it again Withhold food then switch to diet without the offending ingredient Very good if diet can be corrected

Intestinal parasites Roundworms Kittens Diarrhea, weight loss, poor growth Fecal flotation exam Multiple treatments with appropriate wormer; decontaminate environment Excellent with treatment

Hookworms Kittens Diarrhea, vomiting, weakness, pale gums, dehydration, anemia, swollen abdomen, black and tarry stools Fecal flotation exam Multiple treatments with appropriate wormer; decontaminate environment Excellent with treatment

Cryptosporidia Younger cats and those who are immuno-suppressed or have other intestinal problems, eg., Giardia Diarrhea Detection in feces through an ELISA or IFA test Treat any underlying disease; no proven treatment for cryptosporidiosis Symptoms usually go away on their own, but cat may remain infected

Tritrichomonas Young cats, usually in animal shelters or catteries where animals are crowded Chronic soft stools, diarrhea with mucus and straining Microscopic examination of feces; culture; PCR test Ronidazole Very good for individual cat, but very hard to eliminate from a cattery

Coccidia Kittens and those who are immuno-suppressed and kept in crowded conditions Diarrhea with mucus and sometimes blood Fecal flotation exam Sulfa antibiotics Very good

Giardia Usually young cats or those who are immuno-suppressed Mild to severe soft diarrhea with mucus and a bad odor; weight loss, abdominal pain and vomiting; often intermittent ELISA test on feces; fecal flotation exam or microscopic exam of feces; difficult to diagnose - often need multiple samples over several days Metronidazole or possible fenbendazole; bathing and sanitation to remove Giardia from coat and environment Very good but reinfection commonly occurs

Bacterial infection Salmonella, E. coli, Clostridia, Campylobacter Young cats or those who are immuno-suppressed Mild to severe bloody diarrhea with loss of appetite, depression, fever and vomiting Fecal culture and sensitivity Antibiotics; intravenous fluids and supportive care in more serious conditions Good; guarded if infection enters the blood stream (septicemia) or toxins are produced (endotoxemia or entertoxemia)

Viral infections Panleukopenia (feline distemper) Young cats who have not received full series of feline distemper vaccinations and those who are immuno-suppressed Acute diarrhea, loss of appetite, fever, depression, vomiting, dehydration, abdominal pain History, physical exam, white blood cell count Intravenous fluids, antibiotics to prevent secondary bacterial infection, withhold food and water Guarded, especially in young cats

Feline leukemia virus (FeLV) Young cats and outdoor cats Loss of appetite, chronic diarrhea, vomiting, weight loss; may also see many other signs related to disease in other organs FeLV test; History and physical exam; tests (eg., fecal flotation) to rule out other causes Supportive Poor

Feline immuno-deficiency virus (FIV) Adult cats and outdoor cats Loss of appetite, chronic diarrhea, weight loss; may also see many other signs related to disease in other organs FIV test; History and physical exam; tests (eg., fecal flotation) to rule out other causes Supportive Poor

Feline corona virus (FCoV) Young cats, cats in catteries Diarrhea and possible vomiting History and physical exam; tests (eg., fecal flotation) to rule out other causes; FCoV antibody test, electron microscopy or PCR None Symptoms usually go away on their own; however infection could develop into feline infectious peritonitis (FIP)

Feline Infectious Peritonitis (FIP) Young cats, cats in catteries; may be genetic susceptibility in some breeds Diarrhea, fever, lethargy, loss of appetite, weight loss History, physical exam, analysis of abdominal fluid, CBC and serum chemistry Supportive care Poor

Toxins Heavy metals, poisonous plants Those left unattended or unsupervised Loss of appetite, depression, vomiting, dehydration, abdominal pain History and physical exam; tests (eg., fecal flotation) to rule out other causes; testing of feces or vomit for presence of toxin Depends on toxin Depends on toxin

Small intestinal bacterial overgrowth (SIBO); also called antibiotic resistant diarrhea Cats with other intestinal problems Intermittent watery diarrhea, poor growth or weight loss, increased gas, sometimes vomiting History, physical exam, intestinal biopsy, tests (eg., fecal flotation) to rule out other causes, ultrasound, blood tests (eg., serum folate and cobalamin, bile acids) Antibiotics (at least 4-6 weeks); modify diet Guarded; depends on underlying cause

Cancer Lymphoma, adenocarcinoma Middle-age or older Chronic diarrhea, weight loss, poor appetite; may see vomiting and dark, tarry stools History, physical exam, intestinal biopsy Chemotherapy or surgery depending upon the type of tumor Poor

Exocrine pancreatic insufficiency Cats with a history of pancreatitis Yellowish or gray feces sometimes with greasy appearance, increased gas, increased appetite, weight loss Serum trypsin-like immuno-reactivity (a blood test) Pancreatic enzyme replacement therapy; antibiotics to prevent bacterial overgrowth; cobalamin; sometimes diet modification Lifelong treatment required

Idiopathic inflammatory bowel disease Granulomatous enteritis, eosinophilic gastro-enterocolitis, or lymphocytic/ plasmacytic enteritis (LPE) Middle-age Chronic vomiting and diarrhea possibly with blood and/or mucus; sometimes straining, mild weight loss, and/or black and tarry stools, constipation History, physical exam, intestinal biopsy, tests (eg., fecal flotation) to rule out other causes Modify diet; wormers and antibiotics to treat or prevent hidden infections; probiotics; anti-inflammatory drugs; immuno-suppressing drugs if no response to other treatment Guarded

Intestinal obstruction Foreign body, intussusception Diarrhea, vomiting, loss of appetite; as progresses see depression, possible abdominal pain Radiographs or barium series; ultrasound; exploratory surgery Surgery Good if treated promptly; poorer if intestine has been perforated

Irritable bowel syndrome Anxious cats and those under stress Diarrhea with mucus, blood, and increased straining History, physical exam, intestinal biopsy, tests (eg., fecal flotation) to rule out other causes Highly digestible diet with increased soluble fiber; motility medications; decrease anxiety; anti-anxiety medications Guarded

Garbage ingestion or scavenging Outdoor cats and those left unattended or unsupervised Diarrhea, vomiting History and physical exam Withhold food then switch to bland diet and then slowly back to normal diet Excellent

Systemic disease Kidney disease, liver disease, diabetes mellitus Older cats Depression; often vomiting and dehydration; sometimes increased or decreased drinking and urination History, physical exam, intestinal biopsy, tests (eg., fecal flotation) to rule out other causes; complete blood count and chemistry panel Varies with organ system affected; maintain hydration Depends on organ system affected

Hyperthyroidism Middle-age to older cats Increased appetite, weight loss, hyperactivity, increased volume of stools with greasy appearance Blood test for T4 hormone Treatment of hyperthyroidism with methimazole, surgery, or radiation Good with proper treatment

Pancreatitis Siamese may be predisposed Diarrhea, fever, weight loss, vomiting, weakness History, physical exam, CBC and serum chemistry, blood test for TLI, biopsy Supportive, including fluids Depends on severity

Hypo-cobalaminemia (low blood levels of cobalamin) Occurs as a result of severe small intestine disease; diarrhea will not resolve until cobalamin replenished Cats with history of severe small intestinal disease Diarrhea that is nonresponsive to therapy Blood cobalamin level Cobalamin supplementation Good if underlying disease can be successfully treated

Fungal infections Histoplasmosis Diarrhea Biopsy Itraconazole; supportive care Guarded

Short bowel syndrome Cats who have had portions of the small intestine surgically removed Diarrhea unresponsive to therapies History of previous intestinal surgeries Diet modification, cobalamin supplementation, medications to slow movement of food through the intestines Guarded

Cause Example Cats Most at Risk Symptoms Diagnosis Treatment Prognosis