Your Cat’s Digestive System

A variety of disorders - some of them gravely serious - can interfere with its function. Here's how to spot problems.

Your cats digestive system, a complex assemblage of several interdependent components, plays a crucial and multifaceted role in maintaining the animals good health. An essentially tubular arrangement leading from its mouth to its anus, the system – when functioning properly – breaks down the food that the animal has eaten into nutrient-rich particles and facilitates their

Bev Caldwell


absorption while also serving as a barrier against disease-producing organisms that the cat may have ingested.

Unfortunately, this system is vulnerable to many disorders, some of them deadly serious. Indeed, digestive system malfunctions are among the most frequently observed health problems in cats.

An Eventful Voyage

The process that normally takes place in the digestive tract – also referred to as the alimentary canal or gastrointestinal (GI) tract – is launched when a cat takes food into its mouth, chews it into small pieces, and allows it to move to its oral pharynx, the hollow structure at the back of its oral cavity. From there, the food is swallowed, passing into the esophagus – a tube that travels down through the animals chest and opens into its stomach.

Within the stomach, the ingested food mixes with potent acids and enzymes that are produced by the stomach lining and then moves through the pylorus, a sphincter, or ringlike muscle, that constricts or relaxes as needed to control flow into the first section of the small intestine (duodenum). There the food mixes with bile, a bitter yellowish liquid secreted by the liver, and with a fluid produced by the pancreas. These substances and their enzymes play a key role in neutralizing the harsh stomach acids and breaking down proteins, fats and carbohydrates so that they can be absorbed through the intestinal lining (mucosa) and into the cats bloodstream.

From the small intestine, the food passes into the large intestine, which absorbs additional nutrients and also a substantial amount of the water remaining in the ingested food. In addition, the large intestine serves as a storage area for the solid material that is left over after the digestive process. This material – the feces – is eventually excreted from the cats body, through its rectum and anus.

Serious Problems

Some of the most serious problems affecting the feline digestive tract can begin at birth. Among these congenital disorders, says Joe Bartges, DVM, PhD, a professor of medicine and nutrition at the University of Tennessees College of Veterinary Medicine, is a cleft palate – a hole in the roof of the mouth that interferes with the initial stage of the digestive process. And some kittens may be born with an imperforate anus – a usually fatal malformation in which no connection exists between an animals rectum and the outside of its body.

Among mature cats, says Dr. Bartges, the most prevalent feline digestive tract disorder by far is inflammatory bowel disease (IBD). This condition, characteristically evidenced by chronic vomiting and diarrhea, is widely thought to be the consequence of several different disorders involving the feline immune system. Dr. Bartges describes the process involved with IBD as follows: “Something initially damages the lining of the intestinal tract and causes it to leak. As a result, certain large proteins in the animals food, which should be broken down before they are absorbed, are instead absorbed without being digested. Then these large proteins are recognized as alien substances by the immune system that lines the intestinal tract, and that sets off an inflammatory response. Over time, the resulting inflammation damages the mucosa.” Although IBD is most frequently diagnosed in older cats, advanced age, in itself, has not been conclusively identified as a risk factor for the condition, and the disorder can affect animals of any age. And although chronic vomiting and diarrhea are the most common clinical signs of the condition, other indications that a cat is afflicted with IBD include decline in appetite, weight loss, frequent passing of gas, audible rumbling in the gut, difficulty in defecating and blood or mucus in the stool.

“IBD is diagnosed in two-thirds to three-fourths of all feline digestive system diseases,” says Dr. Bartges. However, it is a disease in which morbidity (the incidence of illness) is high but mortality (the rate of death from it) is relatively low, although some affected cats may have to be euthanized due to uncontrollable vomiting, diarrhea and malnourishment.

Dental Origins

In that a cats mouth is considered to be an indispensable component of its GI tract, serious dental disease must be viewed as a disorder of the digestive system. In fact, says Dr. Bartges, dental disease ranks second-highest in prevalence, after IBD, as a source of digestive system illness among cats of all ages.

Among the various dental problems that can affect a cats digestive process, the most common is periodontal disease, which occurs in an estimated 85 percent of cats over the age of six. In this disease, layers of plaque accumulate and harden on a tooths surface. Bacterial poisons and enzymes from the plaque eventually prompt an inflammatory response in the gums that, if untreated, leads to severe gum inflammation (gingivitis). Such an oral infection can, of course, become systemic and ultimately life-threatening. Moreover, a cat with periodontal or any other type of dental disease is likely to have a diminished interest in its food, with potentially severe physiologic and behavioral implications. In any case, such an animals digestive process may well be preempted by the inability to eat.

Additional Threats

Other relatively common disorders of the digestive tract, notes Dr. Bartges, include tumors, which can be either benign or cancerous, and which can develop anywhere within the digestive system or migrate there from other parts of the body. Squamous cell carcinoma, for example, may develop in a cats mouth, he points out. And in the intestine, a tumor can cause a blockage resulting in frequent episodes of vomiting and diarrhea. If such uncontrolled growths remain untreated, they can spread, increase in size and eventually prove fatal.

Inflammatory conditions other than IBD are also frequently seen. They are often caused by infection with such microorganisms as feline immunodeficiency virus (FIV), feline panleukopenia virus (FPV) or – especially in kittens – feline infectious peritonitis virus (FIP). Digestive system inflammation can also result from an allergic reaction to food or an environmental allergen.

In addition, Dr. Bartges and his colleagues often see cats that have failed to successfully disgorge a hairball – a wad of undigested hair that has been moistened with bile and other digestive fluids after being ingested during grooming. Although a cat will normally vomit up a hairball when the mass becomes sufficiently large and irritating, it is possible for a hairball to pass from an animals stomach into its intestine and create a potentially life-threatening blockage.

The feline digestive system, adds Dr. Bartges, is also prone to serious damage resulting from the swallowing of poisonous substances, penetrating bite wounds, falls from great heights and the ingestion of foreign objects, such as sewing needles and spools of thread.

To minimize the chances that your cat will experience a serious digestive tract disorder, Dr. Bartges advises the following: “Make sure that your cat is up to date on its vaccinations. Dont leave small objects lying around that it might swallow. Try to keep the animal away from chemicals that might be poisonous. And see your veterinarian if the animal vomits, has frequent or intermittent diarrhea, or seems to have lost interest in its food.” v