Constipation happens when feces builds up in the colon, hardens and becomes difficult to pass.

The prevailing cause is dehydration. Diseases that can predispose cats to de- hydration include kidney disease, hyper- thyroidism and diabetes. Other causes include anything that results in obstruc- tion of the colon, such as a tumor.

Pain and lack of activity due to osteo- arthritis can contribute to the problem because of difficulty (or disinterest) in getting to water or to the litter box. Being overweight may also reduce a cat’s ability to stay hydrated and fit. Causes not related to physical problems include stress, a dirty litter box or any other reason the cat may not want to go to the bathroom, such as too few clean boxes, location of the box or feeling ambushed by another cat.

Cats typically defecate at least once per day, and feces should be soft and formed. Constipated cats may not defecate every day. They may strain in the litter box and produce little or no feces from their effort; feces that are passed are usually dry and hard. Other indicators include crying or other signs of pain during defecation, vomiting and lack of appetite. Because the colon is so full, the cat might defecate whenever and wherever the urge hits, even if no litter box is nearby.

How we diagnose it

Constipation may be evident based on the cat’s history and physical examination, but your veterinarian may take X-rays to confirm the diagnosis. Other tests that can help identify the cause include blood tests, ultrasound, barium enema, colonoscopy and urinaly- sis (to rule out urinary tract infection).

How we treat it

Treatment depends on the severity of the condition, the cat’s pain level and the underlying cause. The primary treatment is rehydration and maintaining hydration. Removal of the feces via enema and laxa- tives follows rehydration. Although most cats respond well to medical therapy, severe, prolonged constipation may occur (rarely), and this condition may require surgery and can be life-threatening. In well-hydrated cats, constipation is unlikely to recur. If it does, your veterinarian may recommend supplementing the cat’s diet with fiber (e.g., canned pumpkin, bran or psyllium), switch- ing to a fiber-enhanced or low-residue diet, adding water or tuna water to your cat’s food or switching to canned food if you’re currently feeding dry. Medications that can help include stool softeners, laxatives and motility drugs. Manual removal of feces under anesthesia may be required.

Severe constipation may progress to “obstipation,” which is when the colon becomes so impacted with hard, dry fecal matter that the cat can’t pass any feces. Repeated episodes of constipation or obstipation can lead to mega- colon, when the colon becomes stretched due to the large amount of feces and can’t contract to move feces effectively. In addition to the treatments described above, obstipa- tion and megacolon can be treated with intravenous fluids and possibly surgery to remove the affected portion of colon.

How we prevent it

The main way to prevent constipation is to increase your cat’s water intake. Feed a diet with sufficient fiber, offer canned food, avoid obesity, provide plenty of fresh water to drink and offer opportuni- ties for your cat to exercise. Encourage regular bowel movements by providing access to enough clean, large litter boxes throughout your home.

If you notice that your cat has not had a bowel movement in more than 48 hours, consult your veterinarian.