Many things can cause constipation in dogs, and it’s important to consider the complete health of your dog especially if he/she has any existing digestive issues. A dog that hasn’t pooped in a day or two usually has some kind of bowel obstruction, but it can also be a result of other causes.
Although not a comprehensive list, the most commonly seen causes of constipation seen in dogs are:
Stool or Intestinal Impaction
Your dog may have ingested something such as rocks, gravel, sticks, bones, dirt, pieces of toys, clothing or even hair from excessive licking / self-grooming that is caught in their intestinal tract. Sources of high calcium such as bones can contribute to constipation.
Diet
Just like with people, a diet lacking fiber (or too much fiber) is often the cause – but if your dog’s constipation lasts more than 1-2 days, it’s a sign of something more serious.
Dehydration
Not drinking enough water is usually a sign of a more serious underlying illness or issue.
Drugs or Medical Procedure
Constipation is more frequent after certain medical procedures especially if your dog was also administered drugs (such as antihistamines, diuretics, pain relievers), so it’s important to check with your vet if this happens during the post-surgical period.
Anal Gland Issues
A number of different anal gland issues can be the cause, from your dog’s anal sacs being blocked or abscessed (an infection formed by buildup of pus) to masses or tumors that develop on the anus or within the rectum. All of these can cause a physical blockage in the intestinal tract.
Stress or Psychological Issues
Your dog may be bothered by something in the environment that’s causing him/her to hold it in. Dogs tend to defecate less when they’re feeling fear, anxiety or stress. It’s possible that other neurologic disorders may be the underlying cause.
Fractured Pelvis or other Orthopedic Disorders
Fractured pelvis or other orthopedic disorders can make it difficult or even painful for the dog to squat. These are usually accompanied with other symptoms, like limping, a stiff gait, difficulty climbing up or down or yelping from pain.
Intestinal Cancer
Any tumors or masses that develop in your dog’s digestive tract will cause difficulty in passing stool. Other symptoms that usually accompany this are weight loss or blood seen in stool.
Spinal Cord Trauma
Injuries or disease involving the spinal cord may also affect your dog’s central nervous system. Look for signs of an abnormal gait, dragging knuckles or limbs or noticing scuffed nails.
Urinary Obstruction
Because many symptoms and/or signs are similar to those of a urinary obstruction, it’s important to distinguish between a urinary obstruction vs. bowel obstruction and determine the underlying cause.