Constipation in Dogs: Causes and Treatments

View the Things You Didn't Know About Your Pet Slideshow Pictures

Constipation in Dogs: Causes and Treatments

Constipation means absent, infrequent, or difficult defecation. Most healthy dogs have one or two stools a day. This varies with the individual and the diet. A day or even two without stools is not a cause for concern, if the stools remain normal in size and pass without difficulty. But when feces are retained in the colon for two or three days, they become dry and hard, and require forceful straining to pass.

Note that straining also occurs in dogs with colitis, obstructed bladder, and anorectal obstructions.It is important to be sure the dog is not suffering from one of these other problems before treating him for constipation. Colitis, in particular, is often confused with constipation. Remember that a dog with colitis will pass many small stools that contain mucus and/or blood.

Causes of Constipation

Many middle-aged and older dogs are prone to constipation. A common predisposing cause is failure to drink enough water. With mild dehydration, water is withdrawn from the colon, which dehydrates the feces.

Ingesting foreign materials such as bone chips, hair, grass, cellulose, cloth, paper, and other substances is a well-recognized cause of acute and chronic constipation. The indigestible material mixes with feces to form rocklike masses in the colon.

Many drugs commonly used in dogs cause constipation as a secondary side effect. Discuss this possible correlation with your veterinarian. Hypothyroidism is an occasional cause of chronic constipation.

The urge to defecate can also be voluntarily overridden. Dogs develop such inhibitions during housetraining. When left alone in the house for long periods, they often override the urge to defecate. Dogs may also be reluctant to empty their bowels when hospitalized, boarded, or taken on a trip.

Dogs with constipation of recent onset should be examined by a veterinarian. Other reasons to seek veterinary consultation are painful defecation, straining during defecation, and passing blood or mucus.

Treating Constipation

Eliminate or control predisposing causes. Be sure to provide access to clean, fresh water at all times. Constipation associated with ingesting foreign materials such as bone chips can be corrected by eliminating the source and giving dog biscuits to chew on instead. Older dogs with reduced bowel activity can be helped by soaking the kibble with equal parts of water and letting the mixture stand for 20 minutes.

Dogs who voluntarily retain their stool can be helped by providing frequent opportunities for the dog to eliminate. Take the dog outside several times a day, preferably to an area where he is accustomed to going. A mild laxative may be needed when the dog is traveling.


A number of laxatives are available for treating constipation. Osmotic laxatives draw water into the intestines and liquefy the feces. Products containing lactulose, which must be prescribed by your veterinarian, are among the safest and most effective. A mild osmotic laxative effect can also be obtained by adding milk to the diet in amounts that exceed the capacity of the intestinal enzyme lactase to break down lactose into absorbable sugars-in other words, enough milk to cause diarrhea in a dog who is not constipated. The lactose molecule pulls fluid into the bowel and stimulates intestinal motility.

Stimulant laxatives increase the force of intestinal peristalsis. They are highly effective in treating constipation, but repeated use can interfere with colon function. A commonly used stimulant laxative is bisacodyl (Dulcolax). The dose for dogs is 5 mg to 20 mg per day.

These laxatives are used for treating constipation only. If they are given to dog with an obstruction, they can do serious damage. They are not the laxatives of choice for preventing constipation and should not be used every day. Consult your veterinarian before you give your dog any laxative.

Preventing Constipation

Good hydration, a nonconstipating diet, and regular exercise are the best preventives, along with adding fiber to the diet, if needed. A convenient way to provide the fiber is to feed a commercial food formulated for senior dogs. You can also obtain a high-fiber diet, such as Hill's Prescription w/d, from your veterinarian.

Another way to provide additional fiber is to add a bulk-forming laxative daily to the dog's food. Bulk laxatives soften the feces and promote more frequent elimination. Commonly used bulk laxatives are unprocessed wheat bran (1 to 5 tablespoons, 15 to 75 ml per day) and Metamucil (1 to 5 teaspoons, 5 to 25 ml per day). Plain canned pumpkin (1 tablespoon to 1/2 cup, 100 ml) depending on the size of the dog, can also help. Bulk laxatives or pumpkin can be fed indefinitely without causing problems.

Emollient laxatives containing docusate are indicated when the feces are dry and hard, but should not be used if the dog is dehydrated.

Mineral oil is a lubricant laxative that facilitates the passage of hard stool through the anal canal. However, mineral oil interferes with the absorption of fat-soluble vitamins, so daily or frequent administration may cause vitamin deficiency. Mineral oil also reacts adversely with docusate and thus should not be used in conjunction with Colace and the other emollient laxatives. Never administer mineral oil by syringe because it is tasteless and can be inhaled into the lungs.

This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.

Subscribe to MedicineNet's General Health Newsletter

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

Reviewed on 12/3/2009 11:29:49 AM

Health Solutions From Our Sponsors