Constipation (Severe) in Cats

Megacolon in Cats

The colon is the section of large intestine that begins at the cecum, the sac that joins the colon to the end of the small intestine (ileum). From there it proceeds to the rectum in the digestive tract. The main purpose of the colon is to serve as a temporary storage conduit for waste products, extracting water and salt from the waste as it passes through and out of the body. When a condition causes the diameter of the colon to become abnormally enlarged, it is medically referred to as megacolon. This condition is associated with chronic constipation, and with obstipation – severe, obstinate constipation that blocks the passage of gas as well as feces. Minimal colonic activity, where the colon is not releasing its contents, is another condition that can lead to abnormal enlargement of the colon.

Megacolon can be a congenital or acquired condition. Cats with congenital megacolon lack normal smooth muscle function of the colon. Megacolon can also be acquired, such as when feces is chronically retained and the fecal water is completely absorbed. The water and matter bond, and the feces becomes solidified within the colon. If concreted feces remains lodged in the colon for a prolonged period of time, distention of the colon will occur, resulting in irreversible colonic inertia (inactivity). Colonic inertia is characterized by the smooth muscle of the colon no longer contracting or expanding to void feces.

Symptoms and Types

  • Constipation: feces is trapped in the colon
  • Obstipation: severe blockage that impedes both feces and gas, keeping them trapped in the colon
  • Infrequent defecation
  • Straining to defecate with small or no fecal volume
  • Small amount of diarrhea may occur after prolonged straining
  • Hard, dry feces
  • Hard colon felt with abdominal examination (palpation)
  • Fecal impaction can be felt when a gloved finger is inserted into the rectum
  • Occasional vomiting, anorexia and/or depression
  • Weight loss
  • Dehydration
  • Scruffy, unkempt hair coat


  • Unknown (idiopathic) in most cats
  • Congenital (present at birth); the Manx breed appears ot be at higher risk
  • Mechanical obstruction of feces
  • Trauma to the body
    • Limb and/or pelvic fractures
  • Metabolic disorders
    • Low serum potassium
    • Severe dehydration
  • Drugs
    • Vincristine: used for lymphoma and leukemia
    • Barium: used for enhancing x-ray images
    • Sucralfate: used for treating ulcers
    • Antacids
  • Neurologic/neuromuscular disease
    • Spinal cord disease
    • Intervertebral disk disease
    • Disease of the anus and/or rectum


Your veterinarian will perform a thorough physical exam. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, an electrolyte panel, and a urinalysis. The doctor will also perform an abdominal palpation (examination by touch) of the colon, and a manual examination of the rectum, by digital (finger) rectal penetration. You will need to give a thorough history of your cat's health, including a background history, onset of symptoms, and possible incidents that might have precipitated this condition.

Abdominal radiograph imaging is useful for a visual examination of the colon. Recorded images will show whether the colon is full of feces, if there is a mass blockage in the colon, or if there are any other underlying causes of megacolon. An internal examination of the colon, using a lighted tubular instrument called a colonoscope may be performed if obstructive lesions inside the colon, or in the wall of the colon, cannot be ruled out.

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