Constipation In Cats


Chronic constipation is a common condition especially in older cats. A constipated cat passes stool less frequently, with difficulty or not at all. The retained stool eventually distends the colon and if this happens, even for only a few days, the colon’s nerves and muscles become damaged, sometimes permanently. This creates a condition called ‘megacolon’.  Constipated cats often show signs of pain when trying to pass poop. Affected cats make increased trips to the litter tray and spend longer time on it. You see non-productive straining and it can be difficult to decide whether your cat is trying to urinate or defecate. In some instances a cat passes fluid around the impacted stool in the colon. This happens when the retained faeces irritates the lining of the large intestine and stimulates fluid secretion. This can be mistaken for diarrhea. Constipated cats often lose their appetite and vomit as the condition progresses. 

Causes of constipation include:

Litter tray

Reluctance for any behavioural reason, such as a dirty tray or competition from other cats, or any medical reason, such as pain when defecating, to use the litter tray.


Matter such as hair, foreign material or bone in the large intestine.


Cats that are dehydrated reabsorb more fluid from the colon. As a result the stool becomes hard and dry. Chronic renal failure is a common cause of dehydration.


Injuries can damage either the nerves that control contraction of the bowels or the pelvic canal through which the colon passes. Either of these forms of injury can cause constipation. (Some injuries cause the opposite, a lack of sphincter muscle control and consequent faecal incontinence.)

Idiopathic megacolon

In idiopathic megacolon, the smooth muscle that normally contracts to propel the faeces towards the rectum loses its ability to do so. Although the cause is not known, this is, in my experience, the most common cause of constipation in older cats.

Prevention and Treatment

Chronic constipation is a very common problem especially in older cats. Early and uncomplicated constipation usually responds to diet changes and lubricant laxatives. More chronic or complicated constipation is more difficult to control, takes dedication on your part and may require surgery to improve, although surgery is not always a cure.


Laxatives loosen bowel contents to allow stool to pass through the colon. Some act as lubricants while others stimulate the colon to greater activity. Cats should be well hydrated before being given laxatives as most of them lead to water retention in the colon.


Mild constipation may be relieved with a small lubricant laxative. In more severely affected cats we need to give a cat a warm water enema, usually under general anaesthesia. with manual evacuation.

Prokinetic drugs

These improvie neuromuscular transmission and are useful in mild to moderate cases of megacolon. None are licenced for use in cats so they are given with your ‘informed consent’.

Fluid therapy

An intravenous drip is often needed to overcome dehydration. At home, a cat's hydration is improved by switching from dried kibbles to wet food and by adding water to the food. To treat chronic dehydration we can show you how you can give daily subcutaneous fluids.


Surgery is sometimes needed, to remove the permanently damaged portion of the colon.

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