Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

A common sign of megacolon is constipation

Medical therapy with stool softeners is the first-line treatment for this condition

Surgical removal of the colon is indicated if medical therapy has failed

Diarrhea is common just after removal of the colon, however, over a few months the stools become firmer, but likely will not be perfectly normal



  • Megacolon is a functional disorder that is defined as dilatation of the colon or large intestine; this leads to infrequent and difficult passage of feces and constipation
  • There are congenital forms which are present from birth
  • The acquired form is most common
  • Megacolon is found primarily in cats, but also can occur in dogs


Idiopathoic megacolon definition

  • Unknown cause
  • Recurrent and progressives episodes
  • Intractable constipation
  • This is the most common form of the disease


Causes of megacolon

  • Dietary and environmental factors such as foreign bodies in the colon, lack of exercise, and lack of litter box or dirty litter box that the cat does not want to use
  • Painful defecation due to anal sac abscess or stricture of the anus
  • Narrowed pelvic canal
    • Due to previous fracture of the pelvis
    • Intrapelvic tumors
  • Neurologic disease which results is the inability to posture for bowel movements, or nerves controlling the signal to defecate are not working properly
  • Idiopathic – unknown cause is most common
  • Note: Normally cats can retain feces in the colon for a period of several days without harm; if the passage of feces is prevented the colon becomes distended; the duration and degree of constipation necessary to cause megaconlon is unknown


Clinical signs

  • Passage of smaller stools than normal
  • Less frequent defecation
  • Straining to defecate
  • Frequent trips to the letter box which are nonproductive
  • Systemic signs
  • Lack of appetite
  • Depressed attitude
  • Thin
  • Dehydration
  • Vomiting
  • Anemia



  • Occasionally the history and physical examination are enough to diagnose megacolon, but other tests are important to identify a potential cause
  • Rectal palpation may help to identify problems with the anus or pelvis that may be causing the constipation
  • X-rays of the pelvis and abdomen are routinely taken
  • Blood work usually is done in order to evaluate the overall health of the pet in preparation for general anesthesia
  • Below is a radiograph of a cats abdomen (side view) showing impaction of the colon with stool



Treatment options

  • Conservative
    • Stool softeners and lubricating agents
    • Cleansing enemas
    • Manual removal of stool
    • Dietary modification (increased fiber diet)
    • Drugs to increase motility of the colon (cisapride…which recently has become not available)
    • When conservative therapy is not effective surgery is recommended
  • Surgery
    • Removal of the colon
    • The end of the small intestine is connected to the rectum
    • Below is an example of megacolon; the entire colon was removed in this cat


  • Below is a photo taken after the colon was removed and the small intestine was connected to the rectum



Postop care

  • Antibiotics are given short term after surgery
  • Pain medication is usually needed for a couple of days
  • All laxatives are usually stopped
  • Highly digestible food such as Eukanuba Low Residue diet is recommended for the life of the pet; most cats will eat this type of food, however other brands can also be tried
  • Multiple litter boxes should be provided as your pet will need to have convenient access to these to prevent accidents outside the litter box
  • Limit exercise for 3 weeks
  • Watch for signs of infection

Potential complications

  • Short-term
    • Leakage of stool at the site of anastomosis (suture line) of the intestine which results in infection of the abdominal cavity
    • Straining to defecate can take place during the first week
    • Cramping of bowels - signs of this include cat suddenly running, sudden meowing and licking flank or belly; these cramps frequently resolve with time; bacterial overgrowth maybe a cause of this due to excessive gas buildup - metronidazole may be beneficial to decrease the gas production; strictly feeding cats Eukanuba low residue diet may minimize this.
    • Loose bowel movement and increased frequency of BM’s following surgery is expected. This gradually improves over 2 to 3 months.
  • Long-term
    • About 30 to 50% of cats will have increased frequency of defecation for life
    • Most cats will have softer than normal stool for the remainder of their lives
    • Bacterial overgrowth of the intestine presents as gas and diarrhea which usually responds to medication and special diet


Contraindications of surgery

  • Decreased anal sphincter tone before surgery likely will result in an incontinent cat in the postop period
  • Cats that have decreased sensation in the rectum (this is very subjective to evaluate as our patients can’t talk)



  • Generally the prognosis is good and the pet will return to a much happier state of life after surgery has been done

Frequently Asked Questions After Surgery - General Information

When should my cat have the first bowel movement after surgery?

  • Many cats will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a cat will not have regular bowel movements after surgery include:
    • The cat has been fasted prior to surgery
    • Cats do not eat well during the hospital stay
    • They frequently do not eat well when the go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as fentanyl patches, tramadol, morphine) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home a stool softener such as metamucil can be fed
    • Dose of metamucil 1/4 tsp per mixed in with each meal (canned cat food)

My cat had surgery and will not eat.  What can be done?

  • Offer smelly foods that contain fish such as tuna or smelly cat foods
  • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
  • Hand feeding;  place a small amount of food in the mouth so that they get the flavor
  • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature with your finger; it should  be only luke-warm.
  • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
  • Petting and stroking your cat frequently will help to stimulate appetite
  • Remember that most pets will not eat the first day or two after they get home from surgery
  • Appetite stimulants such as cyproheptadine may be helpful
  • If your cat refuses to eat anything for 7 days a stomach tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My cat is vomiting now that he/she is at home.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the cat usually just opens the mouth and fluid or food will be expelled.  Usually the regurgitant will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be happening the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics are a common cause of vomiting after surgery.  In order to see which medication is causing the problem the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • Unusual cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves with holding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then.  In order to decrease the acidity of the stomach Pepcid AC 0.5 mg/kg given by mouth twice daily for 5 days can sooth an upset stomach.  Metoclopramide is a good anti-vomiting medication for cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, which is called esophagitis.  This results in poor motility of the esophagus so water and food will accumulate in this structure.  In most cases esphagitis is self-eliminating and will resolve within two or three days. 
    • Regurgitation also can be caused by a neuromuscular degeneration of the esophagus and this problem will persist.  It is not associated with surgery, rather other underlying diseases.
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus, does not allow passage of food down the esophagus, thus the pet has persistent regurgitation.  This problem should be brought to the attention of your doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent such as sucralfate.  You should consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs as signs can be more subtle and they usually do not vocalize
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs and they should be given only for a few days

Is it okay for my cat to lick or scratch the incision?

  • If a cat licks the incision it will actually delay the healing process because they usually lick too much and traumatize the area.
  • Cats have a barbed tongue, therefore a lot of damage can be done in a short period of time
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Cats will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking/scrtaching the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • If the incision is over the chest an infant tee shirt can be put on your pet and the waist of the shirt fastened in place with an ace bandage or duct tape.
    • If the incision is over the paw or lower limb a bandage or sock could be put on and kept up with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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