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Summary
Constipation is a very common problem among dogs and cats. It happens when a) the stool is too firm, b) when an animal's bowels are not functioning properly, or c) should any other process interfere with normal fecal elimination.
In all cases, afflicted pets are unable to evacuate their bowels fully or comfortably. As a result, they tend to pass feces less often or in smaller amounts than normal and the feces they do pass are typically hard and dry.
A wide variety of causes exist for constipation. Indeed, constipation is considered a disease that's multifactorial in its origin. This means that several causes sometimes conspire to cause constipation. One single causative event or underlying disease is a less common cause of constipation than a conflation of more than one of these.
Consider the following well recognized causes of constipation:
Blockages from foreign materials (e.g., hairballs or ingested toys)
A behavioral reluctance to defecate (e.g., unwillingness to go out of doors due to weather conditions, painful urination, litterbox avoidance as a result of inter-cat stress, a change in brand/type of litter, a full or dirty litterbox)
Pain around the anal area (anal sacculitis is a common cause)
Decreased or insufficient exercise
Decreased water intake
Dehydration for any reason
Inflammatory diseases of the intestinal tract
Nerve damage (e.g., intervertebral disc disease in dogs or trauma)
Back or hind limb pain (making it painful to squat to defecate)
Tumors (that may obstruct the intestines, cause inflammation or lead to nerve damage)
Drugs (including anesthetics and opiates)
Trauma (leading to pain and/or diminished nerve function)
Constipation in dogs may be very common but it's by no means as common or as potentially life-threatening as it is in cats. Cats that experience this more life-threatening version of constipation are said to suffer from a process called "obstipation." This topic will be dealt with in a separate article within this library.
Symptoms and Identification
Constipation will often be readily identified by owners who routinely monitor their pets' elimination habits. Whether by walking their dogs or observing their cats' use of the litterbox, observant owners may note one of the following signs:
Straining to defecate (remaining in a hunched position for longer than usual and exerting repeated abdominal effort)
Production of less stool than normal
Production of harder and/or drier stool than normal
Defecating indoors (dogs) or outside the litterbox (cats)
Passing small amounts of liquid stool (with or without mucus and/or blood)
Vomiting
Lack of appetite
Depression/lethargy
Diagnosis is typically achieved either by owner observation of one or more of the above signs.
Alternatively (and additionally) veterinarians will often be able to palpate the pet's abdomen to identify firm feces in the intestines. In overweight animals, however, abdominal fat can limit a veterinarian's ability to feel fecal material in the intestines. That's why an X-ray is sometimes necessary to identify the problem and assess the degree of constipation involved.
Under more severe circumstances, an endoscopic exam may be necessary to evaluate the large intestine, search for signs of obstruction or other abnormalities and possibly secure a biopsy of the tissues in this area to attempt to understand the underlying disease process(es) involved.
Endoscopy is an anesthetic procedure that involves the use of specialized equipment. These limitations explain why some veterinarians often prefer to refer severely affected patients to internal medicine specialists.
To be sure, veterinarians will also recommend lab work to attempt to identify any underlying diseases that can lead to constipation.
Affected Breeds
All breeds of dogs and cats are susceptible to constipation. However, some genetic influence is, of course, assumed to be a feature of this very common disease.
Treatment
Treatment varies widely depending on the severity of constipation. In the case of simple, uncomplicated constipation, veterinarians may supplement a pet's diet with fiber (consider canned pumpkin, bran or psyllium). But this approach is effective only for the mildly affected.
Here is a list of the most common medical approaches to the less tractable cases of constipation:
Diet has long been considered an important part of constipation management, but it's difficult to determine which diet is best for each patient. Nonetheless, low residue and high fiber diets are typically implemented.
Adding dietary fiber is a common recommendation as well. Psyllium (Metamucil), canned pumpkin or wheat bran are routinely suggested options. Unfortunately, it's likely that this approach is only mildly effective.
Lactulose is a non-absorbable sugar syrup that helps draw water into the colon to help moisten dry stools. This is considered moderately to extremely effective, depending on the patient.
Hydration via intravenous or subcutaneous routes helps moisten the tissues, too.
Medications to help improve the movement
Petroleum-based stool softeners (often marketed as hairball remedies) are popular as well.
In addition to the standard medical approaches are a slew of more intrusive techniques that are often required:
Enemas, in particular, are typically employed when medical therapy is insufficiently effective.
New techniques that offer special polyethylene glycol solutions through nasoesophageal tubes are also available (though typically only in specialty settings)
An anesthetic procedure in which pets' colons are manually evacuated is usually considered a very common last recourse in the case of intractable stool impaction (or when access to specialists is hampered by financial considerations)
Of course, addressing any underlying disease that may create conditions that lead to constipation can help as well.
Further, it's important to note that if this problem constantly recurs, surgical intervention may be the best approach. A procedure called a subtotal colectomy is the gold standard for treating the very most severe cases of constipation in companion animals.
Veterinary Cost
The cost of treatment for constipation depends on the degree to which the individual patient is affected. Mildly affected patients may often be helped at home through the use of simple OTC remedies their veterinarians might recommend. Those less fortunate, however, may find themselves in for hundreds if not thousands of extra dollars every year for specialized diets, drugs and procedures.
Prevention
Prevention of constipation depends highly on its cause. Because it's considered a multifactorial disease with many influences and possible causes, prevention isn't always possible. However, adhering to a strict dietary regimen with plenty of additional fiber and the occasional or indefinite use of laxative-type drugs or products may keep most episodes of constipation at bay.
References
Ramkumar D, Rao SSC. Efficacy and safety of traditional medical therapies for chronic constipation: systematic review. Am J Gastrorenterol 2005;100:936.
Washabau RJ, Holt DE. Diseases of the large intestine. In Ettinger SJ, Feldman EC (eds): Textbook of Veterinary Internal Medicine, 6th ed. St. Louis, Elsevier, 2005.