Constipation in Dogs

by Dr. Audrey Harvey, BVSc (Hons)

Constipation in dogs is defined as difficult or infrequent defecation. If a dog doesn't defecate frequently, the material in his rectum becomes very dry and firm, and hard to pass. He may absorb more toxins from his intestine, which can lead to vomiting and lethargy. If constipation isn't able to be controlled or cured, then the result is obstipation – a permanent loss of function in the colon.

Symptoms of Constipation in Dogs

Most owners notice when their dog is constipated because they are defecating less, or not at all. He may make several attempts to pass a motion, and he may show signs of pain or discomfort. This straining behavior is called tenesmus, and it can also occur with urinary tract disease.

In some cases, affected dogs appear to have the opposite problem, and show signs of diarrhea. This occurs when the impacted feces are blocking the large intestine, and the only thing that can pass around it is thin watery material.

If the dog remains constipated for long enough, he may stop eating, vomit and lose weight.

Causes of Constipation in Dogs

Constipation has many causes, some more common than others. Sometimes there are other things that give you a clue as to what the problem might be. For example, a young pup with constipation may have been born with an abnormality of his intestines. A dog that has problems defecating and is also showing signs of hind leg weakness or paralysis may have a neurological problem that is affecting the nerves leading to his colon. Blood in the feces suggests there may be an ulcer or tumor in the colon that has started bleeding.

One of the most important parts of your dog's examination is a rectal examination with a finger. It's not comfortable, especially when there is something wrong in the colon, so he may need to be sedated for this. Your vet will feel for narrowing of the colon, lumps and bumps that shouldn't be there, and get an idea of just how dry and hard his feces are.

Abdominal X-rays or ultrasound are often very useful to get a good idea of what's happening in his abdomen. These can show up such things as bony obstructions or an enlarged prostate that is blocking the colon. Depending on what your vet thinks is causing the constipation, a colonoscopy may also be necessary. The scope is passed up inside your dog's rectum so your vet can visualize the lining of the intestine. This is useful in diagnosing rectal tumors or strictures that are stopping the movement of feces along the colon.

The main causes of constipation in dogs can be grouped into several categories.

• Metabolic Problems. Electrolyte disturbances or hormonal disorders can lead to dehydration, which will result in hard dry feces. Some examples are hypothyroidism and hypercalcemia. Kidney disease can also have this effect.

• Neurological Disease. If there is a problem with a dog's spine or the nerves controlling the muscles of his rectum, then he won't be able to contract these muscles and expel the feces.

• Pain and Inflammation. A painful prostate gland in male dogs can make them reluctant to defecate. Anal gland disease or perianal fistulas have the same effect. Elderly dogs with osteoarthritis in their hips may find it very uncomfortable to squat, so they don't defecate very often.

• Mechanical Causes. A big meal of bones can result in hard dry feces that are very difficult to pass. A tumor in the rectum may block the passage of feces. Sometimes a dog will eat a foreign body that gets stuck in the colon and prevents the passage of feces.

• Drugs. Some medications are known to cause constipation, particularly the opioid pain relievers such as Tramadol. Antacids, iron supplements and diuretics may also contribute to constipation.

• Behavioral Problems. If a dog is nervous in unfamiliar surroundings, such as a boarding kennel, he may resist passing feces and they may become hard and dry. Constipation also can occur if he doesn't get enough exercise.

Treatment of Constipation in Dogs

Treatment depends on the severity of your dog's condition, and the cause of his constipation.

Mild cases may only need a rectal suppository to soften the feces and lubricate the rectum so feces pass easily. Laxatives given by mouth can also help. Docusate sodium is one such laxative, it draws water into the large intestine, making the feces softer. Liquid paraffin is also often given as a laxative because it makes the feces slippery. However, there is always the risk of it going down the wrong way when it is given to a dog, and causing pneumonia. Laxatives should only be used if your dog isn't dehydrated, because they reduce water absorption in the large intestine and may themselves cause dehydration.

Severely constipated dogs need more aggressive treatment. If your dog is dehydrated, he will be given intravenous fluids. After he is rehydrated, the next step is to remove the impacted feces. This is usually done under a general anesthetic.

When he is asleep, a rubber tube is used to give him an enema. Warm soapy water, or water combined with a lubricant such as KY Jelly, is flushed into his rectum to soften the feces and make them easier to pass. The veterinarian often has to massage his abdomen to help to soften and break up the feces.

It may also be necessary to use sponge forceps to remove the feces. These are long handled forceps which are used to hold sponges during surgery. They can be inserted into the rectum to break off pieces of fecal mass. This needs to be done extremely carefully to avoid the forceps penetrating the bowel wall.

In very rare cases, your dog will need surgery to open the colon and remove the feces that way. This is virtually a last resort, because there is a real risk of the feces contaminating his abdomen, which can lead to a serious case of peritonitis.

Long Term Prevention of Constipation in Dogs

Pumpkin for Dog ConstipationIf your dog has a medical problem such as arthritis that means constipation is a regular occurrence, there are things you can do to keep his feces soft and make defecation easier for him.

A change in diet is often helpful in managing constipation, however there is no one dietary solution for all dogs. Some individuals do best on a low residue food, others prefer high fiber diets. You will need to try each one separately to see which is most appropriate for your dog.

Many dog owners swear by canned pumpkin to add fiber to their dogs' diet and reduce the risk of constipation. Dogs don't seem to mind the taste of it when added to their food.

If a dog has repeated episodes of constipation, it's possible that the stretching of the colon wall has affected its muscles so they don't contract. This results in a colon that just doesn't move feces along and out. He can be treated with a stimulant laxative such as cisapride or bisacodyl. These drugs make the muscle in the wall of the colon contract, which expels the feces. Some laxatives are safe to use long term, others have side effects.

There is no standard treatment for constipation in dogs: it varies with the cause, the severity and whether he is suffering from any other medical conditions at the time. Your vet will work with you to find the solution to your dog's constipation that is best for him.

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