Feline Megacolon: Signs, Causes and Treatment

Your cat's bathroom habits may not be the most pleasant topic, but as any pet parent knows, the litter box is an important indicator of your feline's health. Elimination-related concerns can point to various physical and behavioral issues, so they always warrant a visit to your veterinarian.

One condition, feline megacolon, can result in severe constipation and fecal impaction in the colon, stretching its delicate tissue. Megacolon is a painful condition for cats, and left untreated, it can cause irreversible damage to this important organ. Learn what causes megacolon in cats, how to recognize the signs and how to provide your cat with the care they need; including diagnosis, treatment and prevention methods to help reduce your cat's risk.

In mammals, the colon, also known as the large intestine, has three primary functions: absorbing water and nutrients from digested food, compacting food waste into stool and, finally, eliminating it from the body through the rectum and anus. The colon also supports bacterial fermentation of undigested food, which produces vitamins, gases and other important nutrients. Normally, the colon contracts and distends, involuntarily moving in wave-like contractions that break down food and move it along the digestive tract. Megacolon is a colon disorder that results in a distended, flaccid, dysfunctional colon that cannot contract properly, inhibiting food from moving through the digestive tract as it should.

Megacolon causes fall into three categories: acquired (developed over time), congenital (present from birth) or idiopathic (unknown).

Acquired megacolon is a common form in cats, often resulting from chronic fecal impaction in the colon. If constipated long enough, your cat's poop solidifies into a large, hard mass of fecal matter that distends/dilates the colon. Although it is designed to distend to allow poop to pass through, chronic distention results in irreversible changes to smooth muscle in the colon, severely reducing its ability to contract and move feces through to the rectum. As your cat continues to eat without eliminating, more and more poop backs up in the colon, resulting in abdominal bloating, loss of appetite and pain.

Many conditions can contribute to acquired megacolon in cats, including:

• Colon obstruction, such as from a foreign body, tumor, or pelvic fracture/malformation

• Colon narrowing (e.g., scarring)

• Cancer of the colon or surrounding structures

• Anal sac disease

• Prostate disease

• Perineal hernia

• Trauma to the pelvis, rectum, anus or nervous system

• Tail pull injury, which damages nerves in the tail

• Metabolic disorders, including low blood levels of calcium or potassium and severe dehydration

• Certain medications, including antacids, sucralfate and chemotherapy

Feline obesity and inactivity can increase your cat's risk of developing megacolon.

Congenital forms of megacolon are most commonly seen in kittens and are considered a birth defect. Manx cats are particularly prone to congenital megacolon due to a genetic predisposition to spinal cord abnormalities.

If the cause of megacolon is unknown, it's considered idiopathic. Idiopathic megacolon most likely involves a disturbance of normal colonic muscle function, but more research is needed to fully understand the mechanisms involved.

Cats of any age can be affected by megacolon. The typical signs of megacolon in cats include:

• Straining to defecate or spending more time in the litter box (a sign of constipation)

• Small, hard, dry feces or no feces at all

• A small amount of diarrhea with mucus after straining to defecate

• Occasional vomiting

• Abdominal bloating

• Appetite loss

• Lethargy

• Weight loss

• Scruffy, unkempt coat (due to decreased grooming)

Megacolon can cause dehydration in cats, so they may also exhibit signs of dehydration.