Canine Constipation

Constipation seems like it should be a straightforward medical problem, but this is far from the case! Constipation occurs when there is difficulty or inability to empty the bowels. Stools may be extremely firm. A dog will strain and remain in the “poop posture” for quite some time before producing a bowel movement. In some cases, only mucus will pass.
There are many possible causes, including:

• Eating indigestible material or very dry material such as pork bones
• Arthritis pain that makes “assuming the posture” difficult
• Dehydration
• Malformations of the pelvic canal (congenital or acquired)
• Drugs such as opioids
• Behavioral
• Neurological disease leading to weakness

The normal frequency of bowel movements (BMs) can vary hugely among individual dogs. In general, one to two BMs per day is the minimum, with some dogs going much more frequently. Because the large intestine is such a stretchy organ, a dog can go several days between bowel movements without significant issue. If a dog goes an exceptionally long time without defecating (a week or longer), though, obstipation – a severe form of constipation – can result. This is when the colon is packed with extremely hard, dry feces and passing them is not possible without assistance.

One easy thing to consider any time you are worried about constipation is a fecalith. Sometimes, especially in small dogs with very long hair, a firm fecal ball can become stuck to the hair around the anus and obstruct the outside. In dogs with dark hair, this is easy to miss! This is a quick and simple fix with a pair of scissors and gloves. Anytime you see your dog straining at home, a quick look at the perianal area can identify the cause in some cases.

Symptoms of constipation you might see at home include posturing without producing any feces, straining but producing only small amounts of stool or no stool at all, bright red blood on the outside of the stool (due to inflammation and colon trauma), and in severe cases, decreased appetite and vomiting.

If you suspect constipation, check in with your veterinarian. The symptoms of straining and frequent trips outside might indicate constipation or a urinary problem, which also can be life-threatening.

Preliminary Home Treatment

Home remedies that can help with constipation are numerous and varied in their success. Do not administer over-the-counter laxatives. Instead, you can add plain canned pumpkin to your dog’s food, anywhere from one to two tablespoons per meal. This adds fiber and bulk while increasing colon motility.

If you think dehydration is playing a role, increase your dog’s water intake by adding some canned food to his meals (mix in a little more water for greater effect), dropping a few ice cubes to his water to encourage drinking, and using a recirculating water fountain. A gentle increase in exercise can also improve bowel motility, so take your canine companion for a walk! If this doesn’t accelerate your pet’s gastrointestinal (GI) motility, it’s time to visit a veterinarian.

See Your Vet!

During the examination, your veterinarian will start with a complete history. Questions will include the diet your dog is currently eating including any treats, any medications and supplements that you give, normal frequency of BMs, and what changes you’ve noticed.

Then your veterinarian will assess every system from head to toe. Once the basic system exam is completed, your veterinarian should focus on abdominal palpation and a rectal exam. While it’s not pleasant for your dog (or for you to see!), this is very important. This digital exam can detect many abnormalities and possible causes. It allows the veterinarian to palpate the urethra where it runs underneath the colon, the sublumbar lymph nodes, the prostate (in male dogs), the anal glands, and the mucosal surface of the rectum and colon. The pelvic canal can also be felt.

As with most diseases in dogs, common causes can be ruled in or out based on the signalment (the age and breed).

Very young puppies (less than 6 weeks) with constipation should be evaluated for a congenital abnormality of the rectum and/or colon. Some breeds that may be predisposed include any with short “screw tails” like Pugs and English Bulldogs. When the tail is exceptionally short, there can be underlying spinal abnormalities that cause nerve dysfunction.

Another abnormality is atresia ani, when the anus doesn’t form, and there is nowhere for feces to exit. Puppies who are being bottle raised may also deal with constipation from the puppy milk replacer.

Other Possible Causes

In older puppies who are chewing and eating food, checking for ingestion of foreign material that might lead to fecal impaction is important. This can include sand, rocks, and bone.

Trauma to young dogs that free roam is also a possibility. It isn’t uncommon for a stray pup to be adopted from a shelter situation only to discover old, healed injuries. Pelvic fractures can be one of these types of injuries, leading to a narrow pelvic inlet, and difficulty passing feces.

As dogs age the causes of constipation often become more systemic in nature and may include organ disease such as kidney failure and diabetes mellitus leading to dehydration, neurological disease like  degenerative myelopathy, and arthritis pain can all contribute. This is why a head-to-tail-tip examination is so important!

Reproductive status can also play a role. Intact male dogs develop two particular problems as they age: benign prostatic hypertrophy (BPH) and perineal hernia. Both can lead to difficulty defecating (and urinating).

In the case of BPH, the influence of testosterone causes the prostate to enlarge symmetrically. The condition is not cancerous and non-painful, but if the prostate becomes large enough, it can make defecating and urinating difficult. Treatment is removal of the testosterone source via neutering.

Perineal hernia is also caused by the influence of testosterone. The muscles surrounding the rectum (the perineal muscles) become weak with age and can separate. Abdominal organs, particularly the bladder and colon, can herniate through and lead to difficulty with urinating and defecating. The symptoms are straining and a soft, reducible bulge on one or both sides of the rectum. Again, neutering and surgical repair are the treatments of choice.

Treatment

General constipation treatment depends on the underlying cause. If the constipation is fairly recent in onset, in a young dog, the initial diagnostic testing may just include a physical exam, history, and x-rays to rule out a foreign object. Therapy can then be directed at relieving the discomfort.

Several ways to do this exist including administration of enemas with warm water (sometimes including soap or lubrication), increasing fiber in the diet by adding canned pumpkin or switching to a high fiber diet, increasing water intake, and administration of medications such as lactulose, a stool softener.

If the constipation has been ongoing for a while, and the dog is older, other tests will likely be recommended. These include bloodwork to evaluate for systemic diseases as mentioned above, and possibly an abdominal ultrasound to look for a cause of obstruction.

In severe cases, it might be necessary to manually disimpact. This should be done under heavy sedation and/or general anesthesia. It is painful and invasive, and a dog must be fully relaxed for the best outcome. Prior to disimpaction, the veterinarian may treat with intravenous (IV) fluids to rehydrate first, as well as administer an enema to allow the feces to soften as much as possible. Lactulose may also be added prior to surgery to help with removing the feces. Bloodwork will be reviewed for any electrolyte abnormalities that need correction.

It is not common in dogs, but a condition called megacolon can develop. This describes a syndrome in which there is persistent dilation and slow to no motility. It can happen as a result of long-term, unresolved constipation causing stretching and damage of the nerves. Unfortunately, this can be difficult to resolve. In some cases, the megacolon is reversible if there is a definite underlying cause (such as a pelvic fracture) that can be surgically repaired. The earlier this is done, the better the chances for a good outcome.