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Constipation in Cats

Feline constipation is encountered relatively commonly in veterinary practice, with many possible underlying causes.

This pet health article is intended as a resource for owners seeking further information, discussing what some of these causes might be, explaining the importance of seeking veterinary attention, and detailing how constipation might be investigated and managed.

What is Constipation?

This sounds like a silly question, but the answer might be less obvious than it first appears. ‘Constipation’ is fairly common, and is used to refer to difficulty in passing faeces (poo), or passing faeces incompletely or less often than normal. Often faeces that are not passed will build up in the colon or rectum (the end portions of the bowel), and require veterinary attention.

Constipation is therefore a symptom, rather than a disease in itself, with a huge variety of possible underlying causes.

What are the Signs of Constipation?

As you might expect, the main sign in a cat with constipation is straining to pass faeces. When passed, the faeces are usually small. They might be hard and dry, or they might be liquid with blood or mucus-type material. Cats may feel that ‘they have to go’, and make many unproductive trips to the litter tray. Conversely, some cats may not strain and instead the main sign is going to the toilet less often than usual.

It is very important to be sure that the cat is actually having trouble pooing and not peeing. Although the two can look very similar – a cat straining in the litter tray without producing anything – the body systems (and therefore the problems) involved are very different. Cats, especially male cats, who aren’t able to urinate should be treated as a medical emergency and you should seek veterinary attention and advice immediately.

If they are constipated for a long time, cats may eat less or vomit. Depending on the underlying cause, cats may have other additional signs.


What are the causes of constipation?

Constipation is relatively common in cats, and can happen as a result of…

What the cat eats:

Too much fibre in the cat’s diet can make the faeces overly bulky. Ingesting things like hair, bones, or other ‘non-food’ items may also make the faeces more bulky, a different shape, or may block the colon.


If the cat is losing too much water, or not getting enough in the first place, the faeces will be harder, drier, and more difficult to pass. There are many causes of dehydration, an example could be kidney disease, where the kidneys can’t save water and too much is lost in the urine.

Not exercising enough:

When animals (including humans) walk and exercise, the motion of the abdominal muscles and organs encourages movement of food and faeces through the intestines. If a cat doesn’t walk, either because they don’t want to or they can’t due to another condition, constipation can sometimes result.

Changes around the cat’s environment:

Cats can be sensitive to things we might not think of as particularly stressful, such as changes around the house. Some cats would rather hold it in than go to the toilet in an environment in which they don’t feel safe, or in a dirty litter tray!



It is important that you let your vet know if your cat is currently on or has received medication recently, as some drugs can cause constipation as a side-effect. This includes things which you might not think of as medicines, like iron supplements.

Any condition which makes going to the toilet painful:

These can be problems of the anus or around the anal area; things like narrowing of the anus, abscesses or inflammation, or a condition called anal prolapse, where the very end portion of the intestine (the rectum) is pushed out through the anus.

The cat may also have a condition which makes squatting or trying to go to the toilet painful. An older cat may suffer arthritis which makes them uncomfortable in the squatting position. Injuries are another cause – a bite wound or hurt leg might be obvious enough, but the cat may also have hidden injuries, like a broken pelvis, which can be difficult to appreciate (especially if you didn’t know that the cat had had an accident).



The colon or rectum can be blocked in several ways. Things inside the intestine (this can be bones, foreign objects, or even hard faeces), things within the intestinal wall (for example, a lump), or things compressing the intestine from outside (for example an enlarged prostate, or a previously broken pelvis that has healed in a way that squashes the rectum) can all cause blockages.

Occasionally, a build up of dried faeces in the fur on the cat’s bottom might block the anus from the outside and stop them being able to pass faeces. It’s therefore always important to check your cats anus before you decide to seek veterinary attention.

There can also be other forms of blockage – very young kittens with constipation may have a birth defect called atresia ani, where the opening of the anus has not formed properly.

Diseases of the muscles, or the nerves which control them:

This can be anything that affects the brain or spinal cord, right down to the nerves which branch off from the spinal cord and control the muscle within the bowel walls. It could be injury (to the tail area, for example), or even certain infections and poisons. There is a condition called idiopathic megacolon which is unfortunately fairly common in cats, in which the muscles of the colon do not work properly, and the colon becomes ballooned and unable to push faeces through. The cause is unknown.

As you can see, the number of conditions that can potentially cause constipation is vast!

Your vet will be able to narrow down this long list to the most likely causes by asking some questions about your cat’s lifestyle, medical history, and any other signs that they might have. A thorough examination of the cat is important to look for any external clues or signs which may be related (for example, there might also be a big hard bladder if there is nerve damage, since the nerves allowing bladder emptying branch off the spinal cord near the nerves controlling the colon muscles).

In some cases your vet may need to do further testing to rule out an underlying problem. They may want to do a rectal exam to see if there are any problems that they can feel, like a lump in the rectum or an enlarged prostate. They may want to take an x-ray to check that there are no masses squashing the colon, or to see if the pelvis has been broken. Some masses can only be seen by putting either air or special contrast liquid into the rectum and colon – this effectively outlines the walls of the bowel on the x-ray and highlights any abnormalities. If the cat has other vague symptoms, your vet may take some blood to investigate the possibility of electrolyte imbalance or other organ disease. If there is a possibility of kidney disease, urine tests are also useful (these can help differentiate between a constipation or urination problem too, if there is any doubt). In some cases, your vet can look directly within the bowel using an endoscope (a small camera on a flexible tube, introduced via the anus), and take small biopsies of the colon or any unusual lumps in the bowel for further testing, if needed.


Can we leave the cat, and see if it gets better by itself?

This is not advised. Some causes of constipation might get better without treatment (although the cat may be very uncomfortable or even painful while this happens), but some are potentially very serious and require treatment. Even apparently ‘simple’ cases of constipation should be seen by a vet, as the faeces can become very difficult or even impossible for the cat to pass by themselves. Firstly, what tends to happen is the feces become hard and dry from sitting for a long time in the colon because the body has extra time to re-absorb water from them. Secondly, in the normal situation the colon will try to contract and push the faeces through, but if it becomes overstretched by the build-up for a long period of time, the muscle within the colon wall can start to degenerate and the contractions will be weak. These two events mean that in many cases the cat will need veterinary help to successfully overcome the constipation.


How is constipation treated?

Your cat may be put on a drip if dehydrated to replace lost water, and rehydrate and soften faeces within the bowel. If there are electrolyte imbalances contributing to the constipation, the composition of fluids given can be altered to correct them.

Once rehydrated, the cat can be given laxatives to encourage the faeces to pass. Some laxitives work by drawing water into the bowel from the surrounding body tissues so it is important that your cat is not dehydrated when you give them. This is because the laxative can further dehydrate your cat and make any on going problems worse.

A type of medication called a prokinetic may be given – these work by encouraging the muscles in the intestine to contract and push faeces through. This can be dangerous if there is the possibility of a blockage, so your vet will decide whether prokinetics would be helpful or not depending on the case.

For cats that are recurrently constipated, some owners add liquid paraffin to the food. This is a safe product that can be bought over the counter in most veterinary practices or human pharmacies. It acts as a lubricant in the digestive tract and can help food pass through. The usual dose is 2-5mls twice daily on the food, of course, you should check with your vet before giving any medications or food additives to ensure they are suitable for your cat.

If an underlying cause can be identified, this will require specific treatment.

At home, your vet may suggest measures to help prevent the cat from becoming constipated, like feeding a wet rather than dry food, encouraging activity, and changes around the cat’s home to reduce stress and persuade them to use the litter tray. Diet supplements can be useful; some are bulk-forming and this can stimulate the bowel to contract, but you will remember from the ‘Causes’ section that in some cases too much bulk was the problem in the first place! In cats with a weak and over-stretched colon (due to either a long-standing constipation or Idiopathic Megacolon), the opposite kind of diet is more appropriate – this is called a low-residue diet and causes only small amounts of faeces to be produced. Your vet may initially want to see the cat back for several check-ups, to see how they are doing. It is very helpful if you are able to monitor how hard or soft your cat’s faeces are and how often they are being produced.

If the constipation cannot be overcome with medical treatment or recurs very often, then your vet may offer you the option of surgery. This involves the removal of part of the stretched bowel, with the aim of resolving the constipation. As with any surgery, there are risks, however because it is relatively poorer at healing compared to the rest of the body, surgery of the colon has added risks of wound breakdown and infection. There is also the possibility of post-surgical complications, which includes the constipation recurring or diarrhoea. Obviously this is a big step, and your vet will discuss this with you if they feel it might be necessary.


What is the prognosis for constipation?

This is a difficult question, as it will depend a lot on how long the cat has had constipation and what the underlying cause is. A young and otherwise healthy cat with a simple constipation of short duration, for example, will generally have quite a good prognosis, whereas a cat with a longstanding constipation as part of another disease process may have a poorer prognosis.

For example, if all that is needed is a dietary or lifestyle change then you would expect the prognosis to be good providing those changes are made.

Elderly cats with arthritis type conditions which present as constipation through the inability to squat can be prescribed pain killing anti-inflammatory medications which often significantly reduce pain and allow them to pass motions much easier. The ongoing prognosis for these cases is therefore very good.



Tilly, L.P., and Smith, F.W.K., 2011, The 5 Minute Veterinary Consult: Canine and Feline, 5th Edition, Wiley-Blackwell

http://www.fabcats.org/owners/digestive/constipation.html (accessed 17/06/12)






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