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Megacolon and constipation in cats
Constipation is common in cats: stools stagnate in the colon, dry out and become difficult to evacuate. When the situation repeats itself, the colon becomes distended and its muscle loses its ability to push. We then speak of megacolon: the...
What is it?
Constipation is common in cats: stools stagnate in the colon, dry out and become difficult to evacuate.
When the situation repeats itself, the colon becomes distended and its muscle loses its ability to push. We then speak of megacolon: the colon is permanently dilated and no longer empties properly.
At the megacolon stage, simple constipation becomes a chronic disease that requires long-term treatment, sometimes surgical.
Key point
A cat that pushes unsuccessfully in its litter box must be seen quickly: the distinction between constipation and urinary obstruction is vital, particularly in males.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Repeated and prolonged efforts in the litter box, with little or no stools.
Rare, hard, dry stools, sometimes covered with mucus or blood.
Small amount of fluid or loose stools passed around a hard plug: this does not mean that the cat is not constipated.
Meowing or prolonged squatting during exercise.
Loss of appetite, depression, tense and painful stomach.
Vomiting when stagnation lasts.
The cat may relieve itself outside the litter box because it associates the box with pain.
In chronic forms, weight loss, dull hair and dehydration.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Dehydration is the most common cause: less water in the body, drier stools. Chronic kidney disease or an exclusively dry diet contribute to this.
Pain during defecation: osteoarthritis of the pelvis and spine, old fracture of the pelvis having narrowed the bony canal, anal wound.
Refusal to use dirty litter, poorly placed, too small or fought over by another cat: the cat holds back, the stools dry out.
Mechanical obstacle: mass, shrinkage, clumped hairs in long-haired cats, foreign body.
Damage to the nerves of the colon, particularly after trauma to the tail or pelvis.
Certain mineral imbalances and certain hormonal diseases.
In so-called primary megacolon, no cause is found: it is the muscle of the colon itself which is failing.
Middle-aged to elderly cats, males a little more often affected.
History of pelvic fracture or tail trauma.
Osteoarthritis, which makes defecation painful.
Chronic kidney disease and any cause of dehydration.
Sedentary lifestyle, overweight, exclusively dry diet with little water drunk.
Long-haired cats, which ingest a lot of hair.
Multi-cat households with insufficient litter boxes.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian palpates the abdomen and feels the colon filled with hard material. He systematically checks the bladder so as not to confuse it with urinary obstruction.
An examination of the anal area and pelvis looks for pain, stricture, or a mass.
Abdominal x-rays measure colon dilation and look for an old fracture or obstruction.
A blood test assesses dehydration, kidneys and mineral salts.
Additional examinations are added depending on the context: ultrasound, search for a hormonal disease, examination of the spine.
Treatment
Immediately, the cat is rehydrated by infusion: this is often the action that most effectively softens the stools.
The plug is removed at the veterinarian's office, under sedation or anesthesia, by enemas and gentle manual extraction. This manipulation is painful and delicate: it cannot be improvised at home.
In the long term, laxatives and medications stimulating colon contraction are prescribed, with a dosage adjusted by the veterinarian according to the stools obtained.
The diet is adapted: more water in the ration, moist food, fibers chosen as appropriate. Not all fibers are suitable, some aggravate megacolon.
Osteoarthritis pain, when it exists, must be treated: many cats hold back simply because getting into position hurts.
Litter conditions are reviewed: box large enough, with low sides, clean, in a quiet place, at least one box more than the number of cats.
When the colon no longer responds to medical treatment, surgical removal of the dilated part gives good results and significantly improves the cat's life.
Never administer human laxatives, oils or enemas on your own initiative: some products sold in pharmacies are toxic to cats and a poorly done enema can perforate the intestine.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Increase water intake: wet food, water fountain, several water points away from food bowls.
Brush long-haired cats regularly to limit hair ingestion.
Provide a clean, large, low-sided litter box for arthritic cats, in a quiet place; count one tray per cat plus one.
Encourage physical activity and monitor weight.
Have an older cat's osteoarthritis treated: it is a very underestimated cause of constipation.
Monitor bowel movement frequency; the absence of stools for more than forty-eight hours should alert you.
Possible complications
Transition to irreversible megacolon when the episodes repeat without basic treatment.
Dehydration and mineral imbalances.
Prolonged loss of appetite, with the risk of hepatic lipidosis in a cat that no longer eats for two to three days.
Lesions of the colon wall, bleeding, more rarely perforation during inappropriate maneuvers.
Long-lasting uncleanliness, the cat avoiding the litter box associated with pain.
When to see a veterinarian
Your cat has not had a bowel movement for more than forty-eight hours.
It grows in its litter without producing anything: consult urgently, especially if it is a male, because it may be a urinary blockage which puts its life in danger within a few hours.
He meows or seems to be in pain when pushing.
He vomits, no longer eats, remains prostrate.
His stools are hard, bloody, or passed out of the litter box.
His constipation returns regularly despite the measures taken.
Prognosis
Simple constipation, caught early and the cause of which is corrected, resolves well.
Established megacolon requires lifelong treatment, but many cats are well stabilized by the combination of diet, laxatives and colon-stimulating medications.
When medical treatment is no longer enough, surgery gives good long-term results, with often soft stools for a few weeks after the operation.
Recurrences are common if the underlying cause, dehydration, pain or unsuitable bedding, is not corrected.
Frequently asked questions
How do I know if my cat is constipated or blocked from urinating?
From the outside, this is often impossible: in both cases the cat pushes without result. Urinary obstruction kills within hours. If in doubt, consider it an emergency and have your cat examined the same day.
Can I give him oil or a pharmacy laxative?
No. Many laxatives and enemas intended for humans are toxic to cats, and oil given by syringe can pass into the lungs. Treatment must be prescribed by a veterinarian.
My cat has diarrhea, so he can't be constipated?
Yes. Fluid can leak around a blockage of hard stool and give the illusion of diarrhea. Only examining the stomach can make a decision.
Is surgery a last resort solution?
It is offered when medical treatment is no longer sufficient. It is not a failure: it restores normal life to cats who were undergoing repeated evacuations under anesthesia.
References
AAFP — American Association of Feline Practitioners
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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