Megacolon in cats

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Megacolon in cats is a term to describe an abnormality of the colon, which is the last part of the gut before the anus. With megacolon, the colon loses its motility, which is its ability to move food along the gut and out during defecation. This leads to the colon becoming enlarged and impacted with faeces, leading to the inability to defecate normally and chronic constipation in cats. Cats are either born with it (congenital) or it is an acquired disease later in life, where there are many possible causes. Our vet gives their advice about megacolon in cats in this article.

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Types of megacolon in cats


Kittens can be born with a defect of the colon. Manx cats appear to be at higher risk


  • Idiopathic - megacolon occurs for no apparent reason, usually in middle aged male cats. This is the most common form

  • Mechanical obstruction - food cannot move through the colon as they should leading to dilation of the colon. This can occur due to tumours (benign or malignant) or pelvic injuries that cause narrowing of the pelvic canal, strictures or foreign bodies

  • Nerve / muscle / neuro-muscular junction disorders - spinal cord injuries, feline dysautonomia

  • Chronic constipation and obstipation - this can lead to stretching and dilation of the colon with faeces, which if persistent or recurrent, can lead to megacolon

  • Electrolyte disturbances - low potassium

  • Side effects of certain medications - barium, vincristine

Symptoms of megacolon in cats

The symptoms will depend upon how severe the condition is and the length of time it has been present for, but can include:

  • Constipation - reduced production of stools, stools that are usually hard, dry and difficult to pass

  • Obstipation - complete obstruction of the passage of stools from the body

  • Straining to defecate - sometimes only passing small amounts, or nothing at all, it is also possible for small amounts of diarrhoea to be passed with ongoing straining, or small amounts of blood

  • Vomiting, lack of appetite, lethargy

  • Some of these symptoms may be difficult to spot if your cat goes outdoors and doesn’t use a litter tray. However, on examination your vet can often feel impacted faeces in their colon on abdominal palpation

Diagnosis of megacolon in cats

Your vet will take a thorough history and perform a clinical exam. The next step is often x-rays to view the colon and look for possible causes. They may recommend other diagnostics, such as blood tests, as part of a wider investigation to look for other underlying causes. Colonoscopy (a camera passed up the colon from the anus) may be performed to look for mechanical obstructions, such as tumours, or biopsies taken from the colon wall.

Treatment of megacolon in cats

There are several treatments for megacolon, which will depend upon any underlying diseases and the severity of the condition. When there is obstipation or severe constipation, your cat will require medication to help move faeces through the intestine, such as lactulose. An enema may be needed, which involves an anaesthetic and gentle manual evacuation of faeces from the colon. They also may require intravenous fluids (a drip), pain relief and hospitalisation.

To prevent constipation recurring, treatment of the underlying megacolon is important, and may include:

  • Medical treatments - medication to help the colon wall contract (pro-kinetics), dietary modification, lubricants (lactulose), laxatives or suppositories. It is important NEVER to give human laxatives or suppositories to cats without the advice of a vet, as some can be toxic to cats

  • Pelvic osteotomy - surgery to widen the pelvic canal and allow easier passage of faeces

  • Subtotal colectomy or colectomy - surgical removal of the affected part of the colon, or whole colon. This is required for cases that do not respond to medical treatment

Recovery from megacolon for cats

Some cats respond well to medical management in combination with diet and good monitoring at home to prevent obstipation occurring.

Pelvic osteotomy or colectomy can be curative if successfully performed. Colectomy is not without risk. Surgery on the colon is more likely to suffer from leakage leading to septic peritonitis. After a colectomy surgery, cats can suffer with diarrhoea for weeks to months. This is also known as short bowel syndrome, which in rare cases can be permanent.

Unfortunately if megacolon is prolonged (4-6 months) changes to the colonic wall are permanent and surgery is the only option.

When to see your vet?

  • If your cat may have signs of megacolon

  • To discuss management of megacolon in your cat

Still have questions?

If you would like more advice on nutrition or raw feeding, please book an online video appointment to have a chat with one of our FirstVet nutrition vets.

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