CONSTIPATION, OBSTIPATION, AND MEGACOLON IN CATS
Constipation, obstipation and megacolon are occasional problems for cats.
Constipation is infrequent and/or difficult defecation that leads to retention of feces in the rectum and colon. Obstipation is impaction with harder, drier feces as a result of chronic constipation. Chronic constipation and obstipation can result in megacolon, which is a persistent increase in the diameter of the colon (lower bowel) that does not respond to treatment.
The most common causes for constipation are: 1) reluctance to defecate, because of anal or lower bowel pain or difficulty squatting, 2) inability to defecate, because of fecal factors (dehydration, increased fecal bulk) or colon factors (poor contractions), and 3) physical obstruction, by a mass in the lower bowel or trauma that narrows the pelvis.
Of course, multiple factors can interact in an individual patient. For example, some older cats may be dehydrated from chronic kidney disease and also have arthritis in their hips that makes it difficult to squat. Also, these basic causes can have different causes: dehydration may be due to chronic kidney disease or simply decreased consumption due to dissatisfaction with the water supply.
Straining to defecate and producing hard dry feces are the most common signs a cat is constipated. Some of our patients have other signs that are not so obviously due to constipation. These include:
- defecating outside the litter box
- decreased appetite
- weight loss
- straining to urinate
REMOVAL OF THE OBSTRUCTING FECES For significantly constipated cats and for obstipated cats this usually requires hospitalization for the administration of enemas. Depending on the degree of constipation, the enemas might be a simple rectal injection in an awake patient to a prolonged procedure under anesthesia.
ALLOW THE SMOOTH PASSAGE OF FECES This usually involves chronic administration of some type of laxative(s). An OTC product sold for people, Miralax, is our most common first choice, but there are several to choose from, and sometimes we will use more than one laxative at a time. We typically have owners increase the dose of laxative(s) until the desired soft consistency of the bowel movements is achieved.
REDUCE FECAL BULK Reducing the amount of feces produced is an important part of managing constipation and obstipation. Increasing dietary fiber, which is a traditional recommendation, increases fecal bulk, and this is not our current recommendation. The easiest and most effective way to reduce fecal bulk is to feed only canned food in a measured amount specific for your cat.
ENSURE ADEQUATE HYDRATION Feeding only wet food improves hydration. We can provide a checklist of other methods of increasing a cat’s water consumption.
MANAGE UNDERLYING PROBLEMS At the time of diagnosis of constipation we commonly perform a diagnostic screening profile of the general health of an affected cat. This profile includes a comprehensive history and exam, blood and urine testing, xrays, and sometimes ultrasound exam. It is vital that we identify any underlying problems that are the cause of or contributing factors to constipation; without doing so, it will be difficult or impossible to effectively help our patient. That said, it does sometimes happen that the evaluation does not turn up any abnormalities, in which case the cat’s constipation is termed “idiopathic” (of unknown cause).
MEGACOLON The colon is the lower bowel. Megacolon is an abnormal condition where the diameter (width) of the lower bowel is dramatically increased and there is simultaneous loss of ability to contract normally. The situation could be compared to a balloon that is repeatedly blown up and deflated: each time the air is let out of the balloon, the balloon fails a bit more to return to it’s original small size, until it finally does not contract at all and remains a large loose sac.
By the time we diagnose a cat with megacolon we have often run the gamut of medical treatment options (described above) with unsatisfactory results. The only treatment option that remains at that point is subtotal colectomy - surgical removal of most of the colon.
PROGNOSIS Most, but not all cats with constipation and obstipation can be effectively managed medically. Depending on the underlying cause(s) and other factors, some will require lifelong treatment and others will eventually be weaned off therapy. Unfortunately, a small but significant percentage of constipated cats will eventually progress to megacolon, sometimes despite the best efforts of their owners.