What is constipation?
Constipation is infrequent or difficult passage of stool or feces and is typically a temporary condition. Feces accumulate in the colon (large intestine). Many constipated dogs experience straining or pain when attempting to defecate. Obstipation, a severe form of constipation, is often associated with a serious, permanent, or irreversible medical condition.
One of the major functions of the colon is water absorption, so sometimes the retained stool becomes hard and dry, which makes passing it even more difficult. In some cases, dogs may become dehydrated. Some constipated dogs pass small amounts of liquid feces or blood due to their excessive straining. Sometimes, the liquid feces are mistaken for diarrhea, but in fact it’s a small amount of liquid fecal material that squeezes around the hard fecal mass.
What causes constipation?
There are many potential causes of constipation in dogs. The most common cause of constipation is eating irritating or indigestible substances, such as plant matter or bones. Dogs with long hair or those that lick or groom themselves excessively are also at risk of becoming constipated.
Other common causes of constipation in dogs include:
- Diseases of the colon
- Drugs that cause constipation (such as antihistamines, diuretics, narcotic pain relievers, and sucralfate)
- Fear, anxiety, and other behavioral conditions that alter the passage of normal bowel movements
- Foreign bodies or intestinal obstruction
- Hormonal diseases (hypothyroidism, hyperparathyroidism)
- Inadequate exercise and physical activity
- Megacolon (enlarged colon)
- Neurologic diseases
- Painful conditions that make it uncomfortable to pass stool (e.g., osteoarthritis)
- Pelvic injuries or abnormalities
- Sudden change in diet or ingestion of new foods
- Tumors or masses in the colon or rectum
- Benign prostatic hyperplasia in intact male dogs, or other diseases of the prostate
- Any disease or condition that results in dehydration
What are the signs of constipation?
Most dogs produce feces at least once a day, and many have bowel movements that correspond with daily feedings. If your dog is constipated, they will probably try to pass feces several times, unsuccessfully. You may see your dog circling excessively, scooting (dragging their bottom along the ground), squatting frequently, or even crying out, in severe cases.
Other clinical signs include decreased appetite, vomiting, weight loss, and small amounts of watery feces or feces that contain mucus (without a normal stool). Some constipated dogs have a tense, painful abdomen and will cry or growl if you press on their stomach or lower back. Call your veterinarian if your dog fails to produce a bowel movement within 48 to 72 hours of a previous bowel movement.
How is constipation diagnosed?
Most cases of constipation are diagnosed through physical examination and medical history. When evaluating your dog’s abdomen, your veterinarian will likely feel a firm, distended colon. They may conduct a rectal examination to rule out rectal strictures (a narrowing of the exit passage, resulting from a previous problem), tumors, foreign bodies, or other abnormalities. In many cases, they will perform abdominal X-rays to determine the extent of constipation and whether an obstruction exists.
Blood tests and urinalysis are valuable to search for dehydration, infection, or other conditions that can predispose the dog to constipation. In advanced cases, an abdominal ultrasound may help identify the cause of your dog’s constipation. Biopsies may also be recommended if a rectal mass or stricture is suspected.
How is constipation treated?
Most cases of constipation are relatively easy to treat if caught in the early stages. The first step is to loosen or remove the impacted, hardened fecal matter. Removal may be accomplished using one or a combination of therapies, including enemas, manual removal, and medications. Laxatives such as dioctyl sodium sulfosuccinate (DSS), or polyethylene glycol (PEG) 3350 are commonly prescribed. In cases where an intestinal stimulant, such as cisapride, is required, an obstruction must first be ruled out.
Some dogs may require hospitalization while undergoing multiple enemas or to replace fluids to correct dehydration. More serious conditions may require additional treatments, including surgery or life-long medical or dietary management. Either a low- or high-fiber diet may be needed based on your pet’s specific cause of constipation.
Based on the cause of your dog's constipation, your veterinarian may advise you to feed a therapeutic diet, add supplements or medications to the food, or return for additional tests or treatments. For most dogs, constipation is directly related to eating an unfamiliar food or object and further medical intervention is unnecessary. Other dogs may require lifelong treatment to help maintain normal bowel movements. In all cases, encourage water consumption and limit access to bones.
Dogs that have behavioral or psychogenic causes of constipation may need behavioral modification through training and/or medications. Supplements such as probiotics may also be used after the constipation has been corrected.
When might surgery be necessary?
If constipation is severe and medical treatment is unsuccessful, surgery may be recommended. Surgical treatment involves removal of the affected portion of the colon, a procedure called a partial or sub-total colectomy. This is often a referral procedure performed by a specialist surgeon. The recovery period can be prolonged, and side effects can occur following this surgery, but most dogs do well.
What is the expected outcome for constipation?
The prognosis for constipation is determined by the exact cause. Most dogs will enjoy a speedy recovery after medical treatment has been completed. For dogs with more serious underlying diseases that cause constipation, the prognosis is good once the causative condition has been addressed. Most dogs can be successfully managed through a combination of medical, dietary, and surgical treatments.
A serious, though generally uncommon, consequence or cause of constipation in dogs is megacolon. Megacolon refers to a dilated and weak colon that causes severe constipation. In this condition, the weakened muscles of the colon fail to propel fecal matter out of the colon. This may be due to neurological impairment, problems with the muscles lining the colon, or both.
Megacolon may be seen as a primary condition or a secondary condition following long-term constipation. When the colon becomes enlarged with fecal material over an extended period, its ability to contract may be reduced or lost, resulting in megacolon. Feces accumulate in this abnormally distended and enlarged colon.
