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Prevention is the best medicine when it comes to constipated cats. Plenty of water and a diet with fiber should keep your cat healthy.

Q: Can you please address the topic of cat constipation in your column, especially in older cats and megacolon. 

A: Everyone knows when there is a cat in the hospital being treated for severe constipation. These poor cats have often been unable to defecate for days to weeks, so they are full of firm, hard, fowl-smelling feces. When they reach this point, they must be sedated and the feces manually extracted, releasing this terrible odor into the hospital.

There are many reasons why cats can become constipated. The most common cause is dehydration. When your body does not have enough water, it tries to conserve water any way it can. One way is for the colon to absorb moisture out of the feces. The more water removed, the harder it becomes, making it difficult to pass.

Obviously, anything that impairs the ability of feces to pass out of the anus or makes it painful to defecate will result in constipation. Anal sacs are not as routinely a problem in cats as they are in dogs, but if full, they may result in pain when defecating. Tumors and strictures may impair defecation as well.

The colon passes through the box-shaped pelvis. A fractured pelvis from a dog attack or being hit by a car may both compress the colon and make defecation painful. We have seen cats brought in for constipation from old, healed pelvic fractures that narrowed the pelvic canal. In these cats, constipation may not be an issue until years later.

There are some cat breeds, such as the Manx, which have impaired colonic motility. This makes fully evacuating the colon difficult and sets them up to develop constipation.

Megacolon is the term used when the colon is severely distended and has decreased muscular tone, making full evaluation difficult. This appears to be idiopathic, which is a fancy word for not knowing what caused it, in some cats. It may develop when there is prolonged distention of the colon from another cause, like the old pelvic fracture.

The frustrating part for us is that in the very early stages when we can help, we may not even notice a problem. If you are like me (Perry Jameson) and have multiple cats, you may not notice one going less frequently. By the time I clean the litter box, all of the stool samples are dry and hard. I assume they dried out after sitting in the litter all day, not that they came out that way.

So we usually do not know our cats are having a problem until some other symptoms develop and the problem has reached a more serious level. Vomiting is a common symptom. It does not occur because the cat is so blocked that things are coming up the wrong way, but rather due to nerves on the colon that when stretched trigger vomiting.

Defecating outside of the litter box, straining to defecate and vocalizing when defecating are common symptoms noted in cats with megacolon.

When we suspect chronic colonic distention is a cause, it is important to quickly empty the colon. Warm water enemas and lubricants are often tried first to see if the cat can pass the feces on his own.

When these are unsuccessful, then sedation may be required and the feces manually worked out. More recently we have had some success administering a slow drip through a nasoesophageal tube of MiraLax. This may take 12-18 hours to work, but it avoids the anesthesia and trauma of manual evacuation.

As for every disease, prevention is the best medicine. The most important thing is to make sure your cats have access to clean, fresh water. Cats are finicky about their water, so change it frequently. Make sure it is located in an area where they feel safe (away from dogs). If your cat has a medical condition that can cause dehydration, like renal failure, consider learning to give subcutaneous fluids at home.

By keeping them regular, you prevent the stool just sitting in their colons and getting hard. Make sure you have one more litter box than cat and that they, too, are in safe areas.

Increased fiber intake is healthy for your cat, just like it is for you. Fiber keeps moisture in the feces (keeping it soft) as well promotes a bulky stool, which promotes defecation. Fiber can be from an increased fiber diet, wheat bran, or Metamucil sprinkled on their food, or canned pumpkin.

For cats with recurrent episodes of constipation where dietary fiber does not help, oral laxatives, cathartics and pro-motility medications should be tried.

There are some unfortunate cats that lose all colonic motility and no medical management is effective. When all else fails, the next step is surgical removal of the diseased colon. This sounds radical, but many cats surprisingly do well. Fecal incontinence is rarely a problem. They have a watery stool for about two months, then a mucoid stool for several months and then formed stools at around six months.

With a smaller colon, they defecate more frequently at first, but this gradually drops to normal as well.

Dr. Henri Bianucci and Dr. Perry Jameson are with Veterinary Specialty Care LLC. Send questions to petdocs@postandcourier.com.