Canine Megacolon Awareness


Citizen of Zooville
Megacolon in Dogs

The colon is the section of the large intestine that begins at the cecum, the sac that joins the colon to the end of the small intestine (ileum), and ends where the rectum begins. All are part of the larger digestive tract. The main purpose of the colon is to serve as a temporary storage conduit while it performs the function of extracting useful water and salt from the waste. Megacolon is a condition in which waste is remaining in the colon, causing the diameter of the colon to become abnormally enlarged. It is typically associated with chronic constipation, or obstipation – severe, obstinate constipation that blocks the passage of gas as well as feces. Medically, the colon is described as exhibiting minimal colonic activity – that is, the colon is not releasing its contents.

Megacolon can be a congenital or acquired condition. Dogs with congenital megacolon are born with an abnormal lack of normal smooth muscle function of the colon. Megacolon can also be acquired, such as when feces is chronically retained, fecal water is completely absorbed, and the water and matter bond, causing the feces to become 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 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

  • Idiopathic (unknown)
  • Congenital (present at birth)
  • 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

Congenital megacolon is primarily prevalent in livestock guardian dogs such as the maremma sheepdog, the great pyrenees, and the Hungarian kuvasz, but can occour less commonly in any breed.

Aquired megacolon on the other hand occours more frequently in large yet narrow hipped dogs, as the anal orifice is already small for the body size, and thus more easily obstructed. It can of course occour in any breed however.


Citizen of Zooville
Dogs with megacolon should be fed a raw meat diet. avoid grain based food, as this will compound the problem, and can ferment leading to GDV on top of the underlying condition.
your vet should prescribe a stool softener, and weekly warm-water enemas, instructing you to administer them slowly, and as deeply as possible using a gravity feed bag, and a long soft colon tube, typically 32 to 34fr diameter. water should be warmed to body temperature, (between 100.7 and 101.3 degrees (f).