Diarrhea is defined as the rapid movement of fecal matter through the intestine, resulting in poor absorption of electrolytes, nutrients and water and leading to abnormally frequent and voluminous evacuation of loose, unformed, soft-to-fluid stool. Diarrhea can be acute (come on suddenly) or chronic (lasting more than a week or two). Diarrhea is a symptom, not a disease. It can be caused by any number of distinct medical conditions.
How Diarrhea Affects Cats
Regardless of the exact reason for a cat's diarrheic condition, the effects of diarrhea are fairly consistent and include some combination of the following symptoms:
Loss of appetite (inappetence; anorexia)
Weight loss (uncommon in cats)
Poor hair coat
Brick red gums and other mucous membranes
Pale gums and other mucous membranes
Bad breath (halitosis)
Arched back (due to abdominal pain)
Straining to defecate (tenesmus; more common in dogs; in cats, assess ability to urinate)
Foul-smelling, watery stool; may contain mucus or undigested fat (steatorrhea)
Dark, tarry loose stool (small bowel in origin; contains digested blood [melena])
Greasy, blood-streaked loose stool (large bowel in origin; contains fresh red blood [hematochezia])
Flatulence (passing gas; "farting")
Causes of Diarrhea in Cats
Diarrhea is typically caused by some infectious, chemical or physical irritation of the intestinal mucosa (the sensitive tissue lining the gastrointestinal tract). It takes roughly eight hours for food to pass through the small intestine and into the colon. The small intestine is responsible for absorbing approximately 80% of the fluid from ingested matter, while the large intestine (colon) further concentrates and forms the stool in preparation for defecation. When food passes too quickly through the system, it is incompletely digested, and the liquid component is not fully absorbed, resulting in diarrhea.
A number of things can cause intestinal irritation and the corresponding abnormally rapid transit of ingested material, including:
Internal parasites (hookworms, tapeworms, roundworms, whipworms, others)
Infectious microorganisms (bacteria, viruses, fungi, protozoa; often from recent travel, boarding, hospitalization, trips to the groomer, etc.)
Spoiled, unfamiliar, indigestible or decaying food
Rich, spicy, salty or greasy food
Dead animals (usually rodent or bird carcasses)
Raw meat, fish or poultry
Indigestible foreign objects (sticks, stones, bones, pebbles, cloth, plastic, rug fragments, bottle caps, etc.)
Toxic substances (antifreeze, gasoline, household cleaners, insecticides, rodent bait, toilet bowl inserts, certain wild and domestic plants, certain wild mushrooms, over-the-counter and prescription drugs)
Allergies to or intolerance of certain foods (milk, meat, fish, poultry, corn, wheat, eggs, soy, others)
Stress (visits to the veterinarian, travel, cat shows, introduction of new household pets, household relocation, unfamiliar visitors)
Abrupt change in diet
Unfamiliar water (standing water in puddles or ponds, unfamiliar tap water during travel; protozoal organisms such as Giardia thrive in contaminated water)
Administration of antibiotics or other medications
Intestinal foreign bodies (may or not cause a mechanical obstruction)
Cancer (neoplasia; especially lymphosarcoma and adenocarcinoma in domestic cats; also mast cell tumors)
Irritable bowel syndrome; inflammatory bowel disease
Underlying systemic disease (feline leukemia virus [FeLV], feline immunodeficiency virus [FIV], feline infectious peritonitis [FIP], feline panleukopenia, liver [hepatic] disease, kidney [renal] disease, hypoadrenocorticism [Addison's disease], pancreatitis, hyperthyroidism [common in cats], diabetes mellitus, exocrine pancreatic insufficiency [EPI; more so in dogs], lactase deficiency [intolerance to dairy products; especially prominent in cats], others)
Prevention of Diarrhea
The best way to prevent diarrhea is to avoid the things that cause it. Companion cats should be on a regular de-worming protocol as advised by their veterinarian. Food allergies can be identified by a medically-supervised elimination diet. Dietary changes should always be made gradually. Cats should eat a well-balanced commercial diet, which can include dry kibble, canned food or both. Most veterinarians discourage feeding a raw diet. Cats should be kept away from garbage, rat poison, standing pools of water, dead birds and rodents, chemicals, household cleaners, fertilizer, prescription drugs and other toxins and potentially dangerous foreign objects.
They also should be kept away from sick cats and be housed in a calm, stress-free environment. The litter box should be changed frequently. Food bowls should be washed with soap and hot water after each meal. Antibiotics should only be used when necessary, to promote a healthy gastrointestinal bacterial flora and to reduce the likelihood of antibiotic-resistant bacterial strains. Systemic illnesses should be diagnosed and treated (or at least managed) as effectively as possible. Water from home or bottled water should be used when traveling.
Cats kept in crowded or unsanitary environments are at an increased risk of developing diarrhea. Free-roaming outdoor cats and very young kittens are also predisposed.
Some of the microorganisms that cause diarrhea in cats have the potential to infect people, especially those whose immune systems are weakened or suppressed. These include: Salmonella (bacteria), enterotoxigenic Escherichia coli (bacteria), Campylobacter (bacteria), Giardia (protozoa), Toxocara (roundworms), Ancylostoma (hookworms), Echinococcus, Toxoplasma, Cryptosporidium (protozoa), Tritrichomonas (protozoa), Clostridium (bacteria) and Shegella (bacteria), among others. "Zoonosis" is the medical term for diseases of animals that may be transmissible to humans.
It is essential to identify the underlying cause of feline diarrhea before an appropriate and effective treatment protocol can be developed. In many cases, the source of the problem can simply be removed or avoided – such as removing dietary ingredients that are not well tolerated by a particular cat – and the diarrhea will quickly resolve. If the cause is not readily apparent, the attending veterinarian has a number of diagnostic and management tools available to treat affected cats. Cats become dehydrated very quickly when they lose water through prolonged bouts of diarrhea. If the problem persists for more than 24 hours, the cat should see a veterinarian. The owner should bring along a fresh fecal sample, if at all possible.
The goals of treating diarrhea are to restore hydration, prevent further fluid volume depletion, identify and remove the underlying cause of the condition if possible and prevent passage of infectious microorganisms to other pets and to people.
When presented with a cat suffering from diarrhea, the veterinarian will perform a thorough physical examination, take a complete history and most likely take a fecal sample to check for the presence of internal parasites, protozoa and abnormally high numbers of bacteria in the stool. A number of different techniques are available for fecal evaluation. Other diagnostic tools include a complete blood count and serum chemistry panel, urinalysis, abdominal radiographs, abdominal ultrasonography, fecal culture, urine protein-to-creatinine ratio, serum bile acid levels, serum folate and cobalamin levels, endoscopy, intestinal biopsy and assessment of serum T4 levels (for hyperthyroidism).
If parasites are present, several broad spectrum oral de-wormers are available to remove the adults and their eggs and larva from the cat's digestive tract. It can be difficult to identify protozoa during a fecal assessment, although there are techniques such as iodine staining, centrifugal flotation with zinc sulfate and enzyme-linked immunosorbent assay (ELISA) that improve the chances of finding protozoal organisms in a stool sample.
Most cats with diarrhea will be fasted for 24 to 36 hours, depending upon the severity of their condition and their overall health. They should have access to small amounts of water or crushed ice during this period. They typically will then be started on a bland, low-fat, highly digestible diet with small, frequent meals. Common ingredients include rice, potatoes, tofu, strained meat baby food, yoghurt and/or low-fat cottage cheese. Gradually, the cat's normal diet (or a new one, if recommended by the veterinarian) will be reintroduced over the course of several days. Specific prescription diets are available for cats with diarrhea. These diets are low in fat and contain a moderate amount of fiber. Veterinarians may recommend an elimination diet, if a food allergy is suspected. Novel protein sources - such as venison, fish, duck, rabbit and bison - are increasingly available in commercial feline diets. Dehydrated cats can be given intravenous or subcutaneous fluids to restore normal electrolyte and volume balance.
If the bacterial count in the cat's stool is abnormally high, the veterinarian can prescribe broad-spectrum antibiotics to restore balance of the normal intestinal flora. Metronidazole is a common drug used to treat bacterial diarrhea. Other medications are available to help reduce inflammation, relieve intestinal irritation and pain, soothe the intestinal lining, reduce intestinal spasms, relieve nausea and vomiting, firm up the feces and add bulk to loose stool.
The outlook for cats suffering from diarrhea depends almost entirely upon the cause of their condition, although owner compliance and individual variation in response to treatment can also play a role. Diarrhea associated with an underlying systemic disease, and that caused by ingested toxins, intestinal obstruction or torsion, can rapidly become life-threatening and carries a guarded to fair prognosis. The prognosis for cats with diarrhea caused by cancer depends upon the type of cancer involved. Diarrhea caused by internal parasites, most infectious organisms, dietary indiscretion ("garbage gut"; less common in cats than in dogs), food allergies or bacterial overgrowth from long-term antibiotic use usually is less serious and relatively easy to treat. The prognosis for cats with diarrhea from one of those conditions is good to excellent.