Once food has been digested and the end products of digestion are absorbed in the small intestine, the waste materials and undigested food proceeds to the large intestine or colon where reabsorption of water and electrolytes occurs.
The passage of food and waste materials through the digestive tract is facilitated by the rhythmic movement of the gastrointestinal (GI) tract called “peristalsis or peristaltic waves”.
If there is something that affects peristalsis, the rate in the movement of fecal material in the colon may speed up (such as during diarrhea) or slow down, which can lead to constipation. When water is reabsorbed in the colon, fecal material becomes hard and dry, making it difficult or even impossible to pass. “Concretion” is a term that is often used by experts to refer to stools that are hard as rocks.
There are many causes of constipation in dogs, however, diet is the most significant factor that affects the function of the colon. Veterinarians have classified the causes of dog constipation into three main categories - intraluminal, extraluminal, or intrinsic factors.
Intraluminal Factors
When the cause is intraluminal, it means there is a problem within the colon. This is the most common cause of chronic constipation in dogs. The problem is associated with the inability to pass feces because of a lack of water intake or reluctance to defecate (the dog may have a tumor in the colon or experiences pain when defecating).
Extraluminal Factors
These are factors outside the GI tract that can cause chronic constipation and include conditions that cause the compression of the colon or rectum. Common examples include an enlarged prostate gland, narrowing of the pelvic inlet as a result of a poorly healed pelvic fracture, or the abnormal narrowing of the colon.
Intrinsic Factors
Constipation in dogs may be caused by conditions that affect the digestive system directly, such as with megacolon, or secondary to a primary medical condition like hypothyroidism, hypercalcemia (high levels of calcium in the blood), or lesions in the spinal cord or pelvic nerves.
1. Abnormalities in the diet - lack of dietary fiber, pica (eating non-food items), sudden change in diet, and certain sources of dietary calcium.
2. Senior dogs appear to be more prone to constipation than their younger counterparts.
3. A lack of exercise or a sedentary lifestyle tends to slow down fecal transit.
4. Tumors in the digestive tract can block the GI passage.
5. Issues affecting the anal gland, such as an impaction
6. Enlargement of a male dog’s prostate gland
7. Fluid (dehydration) and/or electrolyte imbalances
8. Medications - Such as antihistamines, diuretics, certain cancer drugs, and antacids
9. Hypothyroidism and certain types of metabolic diseases
10. Stress
11. Disorders of the central nervous system
12. Bone and joint problems, such as arthritis
13. Surgery or post-surgical issues
Most dogs defecate at least once a day. The frequency of bowel movements can be influenced by the number of meals they have each day and how much food they consume. A dog is said to be constipated if the following signs are exhibited:
Below are a few at-home remedies that you can try to help alleviate your dog’s constipation. It’s important to note that if your dog has been constipated for two days or more, it’s time to seek veterinary help. Chronic constipation can quickly escalate into an emergency.
Dogs who have long hair or who shed a lot may have matted hair blocking the rectum and not allowing for the passage of feces. If this is the case for your dog, you can bathe him to soften any stool that may be caught in the hair around his rectum. Also, you can use electric clippers to remove the matted hair.
Please avoid using scissors to cut your dog’s hair in this area, as a cut in the wrong place can require emergency surgery to repair. Veterinarians or dog groomers can help you with constipation due to matted hair if you’re not comfortable doing this at home.
A lack of exercise can be a big contributing cause of constipation in dogs because exercise is required for intestinal movement and digestion. Take your dog for long and/or frequent walks in his favorite places to poop. It may take several attempts, but the more you increase his physical activity, the more you will increase his intestinal activity.
Additionally, if your dog is getting older, it might be difficult for him to support himself in the proper defecting stance. Try using a special harness to help hold up some of his body weight when he begins to posture.
Dehydration is also a major cause of constipation. You can tell that your dog is dehydrated by touching their gums or the inside of their lips. If this feels dry, you should encourage your dog to drink water. Another good way to assess hydration is to pick up the excess skin on the top of his neck (the scruff). If this skin doesn’t quickly snap back into place, your dog may be dehydrated.
Try using different bowls or offering the water at different temperatures to see if this helps entice your dog to drink. Some dogs may show an interest in chewing small ice cubes, although make sure to monitor your dog closely if this is your first time feeding him ice, so he doesn’t try to swallow too large of a piece. Also, a small treat or piece of kibble can be dropped into the water to see if your dog might show some interest in “treat-flavored” water.
Canned pumpkin is a great source of fiber and can be safely added to your dog’s food to help with constipation. The Merck Veterinary Manual recommends adding 1-4 tablespoons of pumpkin per meal to help ease mild constipation.
The amount of pumpkin that you add should be based on the size of your dog: 1 tablespoon for small and toy breeds, up to 4 tablespoons for large and giant breeds. It’s important to use either plain canned pumpkin or pumpkin that you have boiled yourself, not pumpkin pie filling/mix.
Remember, if your dog hasn’t had a bowel movement in over two days, or if he is significantly straining/crying out when attempting to defecate, you should see your vet right away. Home remedies are a great first step, but there is a point where professional medical help becomes necessary.
Also, NEVER give a dog human laxatives. They are far too strong for dogs and can cause emergency complications. There are over the counter medications that can be used to help with constipation, but always consult your vet before giving these. Many can be dangerous or fatal if not properly administered.
Once you have brought your dog to the clinic, your vet will perform a thorough physical exam. A medical history will also be obtained, so be prepared to answer questions about your dog’s diet, activity, symptoms, etc. A rectal exam may be performed to rule out the narrowing of the rectum or the anal opening.
Abdominal x-rays can help determine if there is an obstruction along the GI tract, as well as the extent of constipation. A biopsy may be recommended if there is a mass in the rectum. Blood tests and urinalysis can help determine if dehydration or infection is present.
In all cases of constipation, it’s best to contact a vet for proper assessment and appropriate treatment. If you start to see early signs of possible constipation, bring your dog to the vet immediately. Waiting for further signs can make the condition worse and may require more invasive or aggressive treatment.
Mild constipation in dogs can be treated and managed medically at home. Changing to a highly digestible diet will help speed up the transit of food along the GI tract. Increasing water intake can also soften the feces.
There are medications that can address delayed motility in dogs. Laxatives like Lactulose may be recommended by your vet to help draw out water from the large intestine into the lumen to soften the feces for easier transit. It also mildly irritates the lining of the large intestine to cause more rapid peristalsis. Prescription medications like Bisacodyl speed up the motility of the intestinal tract which helps in passing feces and managing constipation in dogs.
Severe cases of constipation and obstipation in dogs require a more aggressive approach. Dogs that have really hard feces built up in the latter segments of the intestine often require intravenous fluid therapy for proper hydration and hospitalization at the veterinary clinic.
Dogs with obstipation and subsequent intestinal obstruction may need manual removal of the hard feces from inside the intestine. This is usually done through warm saline enemas administered to the dog rectally to help lubricate the dry feces and soften them up.
In severe cases of obstipation, surgical intervention may be necessary. Obstipation cases that have not responded to laxatives, intravenous hydration, and enema treatment are usually a candidate for surgery. Surgical removal via an enterotomy procedure is sometimes the only way to effectively remove hard feces in the intestine. This option, however, is more invasive and would require close monitoring postoperatively.
Though mild constipation can easily be treated with non-invasive treatment and medication, it’s still best to bring your dog to a vet if you’re suspecting that it may be suffering from constipation.
Constipation that has been going on for more than two days warrants prompt veterinary intervention. The treatment regimen may include the following:
Gastrointestinal Diets for Dogs and Cats
A Guide to Treating and Preventing Constipation in Cats
Everything You Need to Know About Diarrhea in Dogs
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