Constipation means absent, infrequent, or difficult defecation. Most healthy dogs have 1 - 2 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 2 - 3 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 or blood.
Many middle-aged and older dogs are prone to constipation. A common pre-disposing 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 With mild dehydration, water is withdrawn from the colon, which dehydrates the feces.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 rock-like masses in the colon.
Dogs can develop constipation from eating wads of grass or from swallowing bones, and cats may get plugged with hairballs. Very furry dogs and cats can get constipated when soft stool forms mats in the long fur around the rectum and mechanically blocks the opening.
Many drugs commonly used in dogs cause constipation as a secondary side effect. Discuss this possible correlation with your vet. Hypothyroidism is an occasional cause of chronic constipation.
The urge to defecate can also be voluntarily overridden. Waste held for a long time against the skin leads to irritation and infection, which can make pets so sore that they don't even try to defecate. Dogs with this problem will often try to defecate while standing up, or may whine, drag their bottoms against the floor, or bite at their rear ends. Dogs can also develop such inhibitions during house training. When left alone in the house for long periods of time, they often override the urge to defecate. Dogs may also be reluctant to empty their bowels when hospitalized, boarded, or taken on a trip.
Dog breeds that have corkscrew tails, like Boston terriers and bulldogs, often have anatomical structures that can interfere with normal defecation. Spiral tail bones tend to extend downward and press against the anal canal, pinching the rectum nearly closed against the pelvis. Besides the typical signs of constipation, these dogs may produce flat, ribbon-like stools. Most cases will require surgery.
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.
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 providing the dog with biscuits to chew 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 while 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 a vet, are among the safest and most effective. A mild osmotic laxative effect can also be obtained by adding milk to the diet - enough milk to cause diarrhea in the constipated dog. The lactose molecule pulls fluid into the bowel and stimulates intestinal motility. Contact your vet for proper dosages.
The mild saline laxative magnesium hydroxide (milk of magnesia) acts in a manner similar to osmotic laxatives. Magnesium hydroxide is contraindicated in dogs with kidney failure.
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 - 20mg per day.
These laxatives are used for treating constipation only. If they are given to a dog with a bowel obstruction, they can cause serious damage. They are not the laxatives of choice for preventing constipation and should not be used everyday. Consult your vet before giving your dog any laxative.
Good hydration, a non-constipating 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 premium food formulated for senior dogs.
Another way to provide additional fiber is to add a bulk-forming laxative to the dog's food daily. Bulk laxatives soften the feces and promote more frequent elimination. Commonly used bulk laxatives are unprocessed wheat bran (1 - 5 tablespoons - 15 - 75 ml per day) and Metamucil (1 - 5 teaspoons - 5 - 25 ml per day). Plain canned pumpkin (1 tablespoon - 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. Examples are Colace (50 - 200mg per day), Surfak (100 - 240mg per day), and Dialose (100mg per day). These products promote water absorption into the feces, thereby softening the stool. They can be used daily.
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. The best way to give mineral oil is to add it once or twice a week to the dog's meal at a dose of 1 - 25 ml, depending on the weight of the dog. Never administer mineral oil by syringe because it is tasteless and can be inhaled into the lungs.
Medications can also be given that influence intestinal motility such as cisapride. These medicines should only be used under veterinary guidance.
One of the best and healthiest ways to prevent constipation is to mix pumpkin into your pet's food. Pumpkin is very high in fiber and has a high water content, and both of these factors help to keep pets regular. Even better, most dogs and cats love the taste, especially of canned pumpkin. It takes only 1 - 2 teaspoons per meal for a cat or dog who weighs less than 15lbs. use 1 - 2 tablespoons for a dog who weighs 15 - 35lbs. Larger dogs will need 2 - 5 tablespoons.
A good practice is to buy jumbo sized containers and freeze a pre-measured amount in muffin papers and thaw them as needed. You will know when you have fed too much pumpkin if your pet's feces have no form and are a pudding-like consistency. If this happens, reduce the amount of pumpkin.
Please contact your veterinarian with questions regarding this condition.
Show Sources & Contributors +
Dog Owners Home Veterinary Handbook
Publisher: Wiley Publishing, 2007
Authors: Debra M. Eldredge, Liisa D. Carlson, Delbert G. Carlson, James M. Giffen MD
The First Aid Companion for Dogs And Cats
Publisher: Rodale Inc, 2001
Authors: Amy D. Shojai, Shane Bateman DVM