Constipation, Obstipation and Megacolon
General information
The cat’s digestive system consists of the oral cavity, esophagus, stomach, small intestine, cecum, large intestine (also called the colon), and rectum. The colon is where electrolytes and water are absorbed and where feces are stored before being expelled through the rectum.
Constipation is a condition in which fecal matter remains in the colon for longer than it should. This leads to difficult, infrequent, and often painful defecation of dry, hard stool. Over time, unmanageable constipation can lead to obstipation. In obstipation, the colon has become impacted with feces and defecation has become impossible. Megacolon refers to a persistently dilated, damaged colon which results in chronic, severe constipation/obstipation.
Causes
There are many different causes of constipation. Some of the more common causes are:
• lack of exercise
• obesity
• dehydration (due to disease or inadequate water intake)
• certain medications (including antihistamines and diuretics, among others)
• dietary changes
• litter box changes (which may make a cat reluctant to use their box), and hairballs
Note that if any of these problems persist for long enough, obstipation may result.
Other causes of constipation/obstipation that are frequently seen in cats include tumors, foreign bodies, and scar tissue in the abdomen. Also, any disease that disrupts the body’s electrolytes may lead to constipation/obstipation. Common diseases in cats that may cause this are kidney disease and diabetes.
Sometimes an injury can even lead to constipation/obstipation. A fractured pelvis or an injury of the spinal cord may make defecation painful or impossible.
In megacolon, the cat’s colon has become persistently dilated and the colon’s structure has been severely injured, resulting in chronic constipation/obstipation. Megacolon may be acquired or idiopathic (which means we do not know what the underlying cause is). Acquired megacolon may result from chronic, prolonged distention of the colon due to constipation/obstipation. This prolonged distention can permanently damage the colon’s muscles and nerves, which then impairs the ability of the colon to move feces along its path. The resulting inertia of the colon then prevents feces from being expelled from the rectum. Idiopathic megacolon is thought to involve a loss of function of the smooth muscles of the colon, again resulting in inertia of the colon. With early treatment, acquired megacolon may be reversible, while idiopathic megacolon is not. Note that Manx cats may be predisposed to megacolon.
Cardinal symptom
Painful, reduced, or absent defecation
Symptoms
Cats suffering from constipation/obstipation will often be seen straining to defecate, but will produce little or no feces. The feces that are produced will usually be hard and dry. Sometimes a small amount of watery or mucousy diarrhea may be passed around the retained feces. Cats may cry out when trying to defecate, and may spend a great deal of time in their litter boxes. With prolonged constipation/obstipation, cats will lose their appetite and become lethargic and depressed. Vomiting, dehydration, an unkempt haircoat and weight loss may also be seen. Sometimes the abdomen will be distended and painful to touch. In severe cases of constipation/obstipation, the cat can get systemically ill, which can be life-threatening.
Diagnosis
A thorough physical exam by your veterinarian will be needed for diagnosis. Abdominal palpation during the exam may reveal an enlarged colon full of hard feces. Abdominal x-rays are also often recommended to confirm the diagnosis and help determine the underlying cause. Bloodwork and ultrasound studies may also be recommended. After enemas to clean the colon have been given, further tests, such as barium enemas or colonoscopy, may also be recommended to identify underlying problems.
Treatment
In mild cases of constipation, oral medication may be all that is needed to take care of the problem. In these cases, stool softeners and/or laxatives may be prescribed, and a change in diet may be recommended.
In more severe cases of constipation/obstipation, enemas will usually be required. If manual extraction of the feces is also necessary, the cat will need to be sedated. Fluids may also need to be given for dehydration. Antibiotics , as well as stool softeners, laxatives, and a change in diet, may be prescribed in these cases. Medications that stimulate the motility of the colon may also be recommended, especially in cases of megacolon. Any underlying cause of the constipation/obstipation should, of course, also be treated.
Cats with megacolon, or those that for some other reason have frequent or chronic constipation/obstipation, may need to be on medications and a special diet for the rest of their lives. In cases that do not respond to diet and medication, surgery to remove a portion of the colon may be necessary.
Prevention
Make sure your cat always has access to plenty of clean, fresh water. Encourage your cat to be active, and do not allow your cat to become overweight! If your cat is overweight, start it on a gradual weight loss program involving more activity and fewer calories. Brush your cat frequently to decrease the chance of hairballs.
Tips
Cats that are straining to urinate (which can occur with urinary tract obstruction) can look very similar to cats that are straining to defecate. Either situation can be very serious, and should prompt you to seek veterinary care for your cat right away.
Never give your cat an enema at home. The lining of the colon can be seriously damaged by improper enema techniques, and some of the over-the-counter enemas that are safe for people can be life-threatening in cats and dogs (e.g., Fleet enemas).