Constipation in Cats

By Malcolm Weir, DVM, MSc, MPH; Ernest Ward, DVM

What is constipation?

Constipation is defined as an abnormal accumulation of feces in the colon resulting in difficult bowel movements. This may result in reduced frequency or absence of defecation. The feces are retained in the colon (large intestine). Since one of the major functions of the colon is water absorption, the retained feces become hard and dry, which makes passing the feces even more difficult. Constipated cats will strain in an attempt to defecate, resulting in abdominal pain. Some constipated cats may pass small amounts of liquid feces or blood because of excessive straining. Sometimes, the liquid feces are mistaken for diarrhea, but in actuality, when the cat strains, a small amount of liquid fecal material is able to squeeze around the hard fecal mass.

What causes constipation?

Constipation is a condition seen most commonly in mature, middle-aged cats, although it may occur at any age. Factors associated with the development of constipation include:

  • hairballs, especially in longhaired cats
  • ingestion of foreign bodies such as bones
  • pelvic injuries resulting in a narrowed pelvic canal
  • obesity and/or lack of exercise

In some cases, there is no obvious cause identified. Constipation is a common symptom associated with idiopathic (unknown cause) megacolon.

What is megacolon?

Megacolon (a term referring to a dilated and weak colon that causes severe constipation) is the most common cause of constipation in cats. In this condition the weakened muscles of the colon fail to propel fecal matter out of the colon. This may be due to neurological impairment, problems with the muscles lining the colon, or both.

Megacolon may be seen as a primary condition or secondary condition following long-term constipation. When the colon becomes distended with fecal material over a prolonged period, its ability to contract may be reduced or lost resulting in megacolon. Feces then accumulate in this abnormally distended and enlarged colon. See the handout "Megacolon in Cats" for more information on megacolon.

How are constipation and megacolon diagnosed?

In most cases, a diagnosis of constipation can be made on the basis of the cat's clinical signs and medical history. Affected cats usually strain unsuccessfully to defecate, and may cry in pain. Any feces passed are hard and dry. The cat may also show signs of lethargy, reluctance to eat, abdominal pain and distension, and vomiting.

Unless your cat is obese or tense, your veterinarian can often palpate or feel the accumulated fecal material in the colon. Further tests may be needed in order to diagnose the cause of the constipation. These may include abdominal and pelvic radiographs (X-rays) to look for pelvic injuries, colonic strictures (a narrowing of the exit passage, resulting from a previous problem), or tumors, as well as bloodwork and urine testing to look for underlying disease conditions that can contribute to constipation. Radiographs are also the primary test for the diagnosis of this condition.

 How can constipation and megacolon be treated?

Treatment varies depending on the cause of constipation. If an obstruction such as a colonic tumor is present, surgery may be required.

Initial treatment of a cat with constipation may involve administration of enemas and manual extraction of feces by a veterinarian. Removal of feces from the colon often requires an anesthetic or sedative. Intravenous fluid therapy is usually required to correct fluid imbalances and dehydration that worsen the constipation. If the constipation recurs or becomes a long-term problem, dietary management or medications may be needed to prevent recurrence. A number of treatments are available to soften the feces and promote regular bowel movements. In mildly affected cats, high fiber diets, lubricating laxatives, or stool softeners may prevent recurrence.

Those more severely affected may need drugs that stimulate contraction of the colon. The dose of these drugs is adjusted as needed to produce the desired effect. Ideally, cats should defecate at least once every other day. Over time, resistance to the treatment and medications may develop, necessitating an increase in the drug dosage or a change in therapy. You should not make changes to your cat's treatment protocol without consulting your veterinarian.

"You should not make changes to your cat's treatment protocol
without consulting your veterinarian."

It is important to ensure that there is always access to a clean litterbox so that frequent defecation is encouraged. In longhaired cats, regular grooming may reduce hair ingestion, while "hairball remedies" or hairball diets may lessen the likelihood of hairballs causing constipation.


When might surgery be necessary?

If megacolon develops or if the constipation is severe and medical treatment is unsuccessful, surgery may be recommended. Surgical treatment involves removal of the affected portion of the colon, in a procedure called a partial or sub-total colectomy. Most cats do very well with few side effects following this surgery.

What is the long-term outlook for a cat with this problem?

The long-term outlook varies according to the cause of the constipation; however, most cats can be adequately managed without surgery and resume normal, healthy lives. For cats that require surgery to correct megacolon, the prognosis is good.

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