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Body system: Stomach, gut and digestion. One of the core guides in our dog health conditions library. If your dog has worrying signs right now, start with our symptom triage guides.
Constipation means infrequent or difficult passing of stool, with the stool that does arrive typically dry and hard. The colon absorbs water from its contents, so the longer material sits there, the drier and harder it becomes, and the harder it is to pass: a self worsening cycle. Most owners notice the behavior before the stool: the dog squats and strains repeatedly, produces small hard pellets or nothing at all, may cry out, circle, scoot, or keep asking to go out.
Vets separate three points on one scale. Constipation is the simple, usually short lived form. Obstipation is intractable constipation, where a mass of dry, hard feces is retained and the dog cannot evacuate it without help. Megacolon is the end stage structural problem, a colon that has stretched and lost its muscle strength, so it can no longer push contents along effectively; it is less common in dogs than in cats but does occur after long standing or repeated episodes. A common trap deserves naming at the start: a dog straining may not be trying to pass stool at all. Straining to urinate, especially a male dog straining with little or no urine, looks similar and is a urinary emergency, not constipation. Watch what the dog is actually trying to do.
Causes group into three families. Inside the colon: poorly digestible firm material such as hair, bone fragments or litter mixed with feces, too little water intake, and reluctance to defecate because of pain, a dirty toileting area or stress. Pressing from outside: a narrowed pelvis after an old fracture, enlarged lymph nodes, and, in intact males, an enlarged prostate squeezing the rectum. Problems with the machinery itself: megacolon, spinal cord or pelvic nerve injury, low thyroid, and electrolyte disturbances such as low potassium or high calcium. Medications are a frequent overlooked contributor: opioids, diuretics, antihistamines, anticholinergic drugs and some antacids all slow the colon. Older, overweight and less active dogs, and dogs recovering from anal gland or orthopedic pain, are presented more often.
Breeds and dogs at higher risk: No single breed defines constipation, but flat faced breeds such as Bulldogs, Pugs and Boston Terriers, toy breeds and Dachshunds are reported to experience it more frequently in AKC guidance. Intact older male dogs of any breed carry the prostate related risk.
Diagnosis usually starts with the history and a physical examination including abdominal palpation, where retained feces can often be felt, and a rectal examination, which in males also assesses the prostate and checks for narrowing, masses or pain. X-rays show how much feces is retained, whether the colon is enlarged toward megacolon, and clues such as bone fragments or an old pelvic injury. Dogs with chronic or recurring constipation get bloodwork including thyroid testing, and a neurological check, because treating episodes without finding the driver guarantees another episode.
Mild, recent constipation in a dog that is otherwise well is managed with hydration and movement: ready access to water, regular walks, and feeding on your vet's advice, sometimes with added dietary fiber, which vets generally prefer over other laxative approaches because it is well tolerated and works with normal gut function. Your vet may suggest a specific stool softener or osmotic laxative for your dog. Never give a home enema, and never use a human laxative or a phosphate containing enema product without veterinary direction: technique and product choice matter, enemas are given in the clinic with sedation when needed, and laxatives given to a dehydrated dog can make dehydration worse.
Obstipation is clinic work: rehydration first, then enemas or careful manual removal of the mass under general anesthesia. The underlying cause is treated in parallel, for example castration or medication for an enlarged prostate (see our prostate disease guide), thyroid treatment, or a medication review. Long term control usually combines a higher fiber diet or a prescription gastrointestinal diet, weight management, scheduled toileting opportunities, and prompt attention to the first missed day rather than the fourth. Megacolon that no longer responds to medical management is occasionally managed surgically by removing most of the colon, a referral decision made only after medical options are exhausted.
Track the rhythm: most adult dogs pass stool once or twice daily, and knowing your dog's normal pattern is what makes a change visible early. Keep water bowls filled and cleaned, build toileting breaks into the day rather than expecting one long hold, and keep long coated dogs trimmed around the rear so matted hair cannot mechanically block the exit, a simple and genuinely common cause. If your dog has one episode, review what changed: diet, medication, exercise, pain, or access to bones and chews, and mention it at the next visit even if the episode resolved.
See also: symptom triage guides | All conditions A-Z | Health hub
Call your vet if there is no bowel movement within 48 hours, and sooner if your dog is straining unproductively, uncomfortable, off food or vomiting. Straining to urinate with no urine is an emergency the same hour, not a constipation wait.
Plain pumpkin is a fiber source vets commonly suggest for mild cases, and it is a reasonable question to ask your vet about for your dog. It is not a treatment for obstipation, a blockage, or a straining dog that may be trying to urinate, and those need the clinic, not the pantry.
Constipation is difficult passing of dry, hard stool. Obstipation is constipation that has become intractable, with a retained mass the dog cannot pass. Megacolon is a stretched, weak colon that has lost the ability to move stool, often the result of long standing episodes.
Liquid can leak around a hard, retained fecal mass while the mass itself stays stuck. It looks like diarrhea but the problem is the opposite. A vet examination and often an X-ray sort it out quickly.
Yes. Prostate enlargement, low thyroid, spinal problems, pelvic injuries, medication effects and dehydration all present as constipation. Recurring episodes should always trigger a search for the driver, not just another softener.
This page is general information drawn from the published guidance of the organizations listed under Sources below. It is not veterinary advice, and it does not replace your own veterinarian, who knows your dog. If your dog may have eaten something toxic, contact your veterinarian, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661 straight away. A consultation fee may apply on the helplines. If your dog is struggling to breathe, has collapsed, is having a seizure that will not stop, or has a swollen belly with retching that brings nothing up, go to an emergency veterinarian now and do not wait to finish reading.
Last updated: November 2026. Facts on this page were checked against the sources listed above. How we work: our methodology.