Constipation in cats means infrequent, hard, or difficult bowel movements, and when it becomes chronic the colon can stretch and lose its ability to contract—a condition called megacolon. Mild constipation often responds to hydration, diet, and laxatives, but a cat straining for more than a day or two needs veterinary care before it worsens.
Last reviewed: June 2026
What Is Constipation and Megacolon in Cats?
Constipation is the infrequent or difficult passage of hard, dry stool, while megacolon is the end-stage result of chronic constipation in which the colon becomes permanently dilated and weakened. In a normal cat, the colon contracts to move stool along; when stool sits too long, the colon absorbs more water, the feces harden, and passing them becomes painful. Over months of repeated episodes, the colon muscle can stretch beyond recovery and stop contracting effectively.
Megacolon is the most severe and frustrating form, because the colon can no longer empty itself even with stool softeners. As described in Ettinger's Textbook of Veterinary Internal Medicine, middle-aged male cats are over-represented, and a large share of megacolon cases are idiopathic, meaning no single cause is found despite a thorough workup.
What Are the Signs of Constipation in Cats?
The clearest sign of feline constipation is repeated straining in the litter box that produces little or no stool. Owners sometimes mistake this straining for a urinary problem, which is dangerous because a urinary blockage is a true emergency.
Signs to watch for include:
- Straining in the litter box with little or no stool
- Small, hard, dry fecal pellets
- Fewer than one bowel movement per day (or none for 2+ days)
- Crying or vocalizing while defecating
- Reduced appetite and lethargy
- Occasional vomiting
- A hard, distended belly
Because urinary obstruction can look similar from the outside, any cat repeatedly straining and producing nothing should be checked promptly to rule out a life-threatening blocked bladder.
Why Does It Happen?
Constipation develops whenever stool moves too slowly or the cat becomes dehydrated, allowing the colon to pull out too much water. Common contributors include inadequate water intake, chronic kidney disease, obesity, ingested hair, painful arthritis that makes posturing difficult, pelvic injuries that narrow the canal, and low dietary fiber or moisture. As outlined in the WSAVA Global Nutrition Guidelines, 2011, adequate moisture and a balanced, species-appropriate diet are foundational to preventing recurrence.
When no underlying cause can be identified and the colon has lost its tone, the condition is termed idiopathic megacolon.
How Is It Treated?
Treatment depends on severity, ranging from simple home measures to hospitalization. For mild cases, vets focus on hydration, dietary changes, and stool softeners.
- Increase water intake with wet food, water fountains, or added moisture
- Stool softeners and laxatives such as lactulose, dosed to effect
- Prokinetic drugs to stimulate colon contraction in chronic cases
- Enemas and manual deobstipation under sedation for severe impactions (never use over-the-counter human enemas, which can be toxic to cats)
- Subtotal colectomy surgery for true megacolon that no longer responds to medical therapy
Many cats are managed long-term with diet and medication, while end-stage megacolon may ultimately require surgical removal of the affected colon, which carries a good long-term prognosis. Routine wellness checks help catch contributing diseases early, as recommended in the AAHA Preventive Healthcare Guidelines, 2011.
When to See a Vet
Call your vet today if:
- Your cat has not passed stool in more than 48 hours
- Your cat is straining repeatedly but producing little stool
- You notice reduced appetite, lethargy, or occasional vomiting
Go to the ER immediately if:
- Your cat is straining and producing nothing and you cannot tell if it's urine or stool
- Your cat is vomiting repeatedly and won't eat or drink
- Your cat is weak, collapsed, or in obvious pain
- The belly is hard, painful, and severely distended
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Frequently Asked Questions
How long can a cat go without pooping before it's an emergency?
A cat that hasn't passed stool in more than 48 to 72 hours should see a vet, and one straining without producing anything needs urgent evaluation. Prolonged constipation lets the colon harden the stool further and can progress toward megacolon, so it's better to intervene early than to wait and hope it resolves on its own.
What can I give my cat for constipation at home?
Only give remedies your veterinarian approves—never human laxatives or enemas, some of which are toxic to cats. Safe first steps include switching to or adding wet food, encouraging water intake, and, if your vet directs, a measured dose of a cat-safe stool softener such as lactulose. Always confirm it isn't a urinary blockage first.
How much does treating cat constipation or megacolon cost?
A basic exam runs $50–150, with bloodwork $100–250 and x-rays $150–400 to assess stool load. Sedated manual deobstipation typically costs $300–800, while subtotal colectomy surgery for true megacolon runs $1,500–4,000 or more. Ongoing medical management with diet and laxatives is far cheaper than repeated crisis cleanouts.
Can cat megacolon be cured?
Idiopathic megacolon usually can't be cured medically because the colon muscle has permanently lost its ability to contract, but it can often be managed for a long time with diet, laxatives, and prokinetic drugs. When medical management fails, surgical removal of the diseased colon (subtotal colectomy) is curative for most cats and carries a good prognosis.
Why does my older cat keep getting constipated?
Older cats are prone to constipation because of declining kidney function and mild chronic dehydration, reduced activity, arthritis that makes squatting painful, and sometimes underlying megacolon. Each episode that lets stool sit longer makes the next one more likely, so consistent hydration, weight control, and managing arthritis pain are key to breaking the cycle.
Still Not Sure if Your Cat Needs a Vet?
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