Constipation is a condition most commonly seen in middle-aged and senior cats, and in entire male dogs with prostatic enlargement. It’s an uncomfortable and frequently very painful condition resulting from an abnormal accumulation of faeces leading to difficulty in passing bowel motions. This may result in reduced frequency or absence of defecation, and/or excessive straining to defecate.

The faeces are retained in the large intestine, the colon. One of the functions of this part of the bowel is water absorption. In a constipated cat, the retained faeces become hard and dry, which makes passage even more difficult and painful. Paradoxically, some constipated animals may also pass small amounts of liquid faeces.

Causative factors associated with constipation in cats include:

  • Excessive hair in the stool, especially in long-haired cats, and cats with a flea allergy
  • Ingestion of foreign bodies.
  • Obstruction caused by tumours, strictures or masses compressing the large intestine.
  • Pelvic injuries, most commonly after a road accident, resulting in a narrowed pelvic canal.
  • Damage of the nerves which cause the colon to contract. This may arise following traumatic damage such as a road accident, or may be seen as part of more generalised neurological disease.

In some cases, there is no obvious cause but in all cases of extended or severe constipation the affected cat will require treatment at the hospital.

Frequently associated with constipation is megacolon, the term for a dilated and poorly motile colon. When the colon becomes distended with faecal material over a prolonged period  its ability to contract may be reduced or lost, resulting in megacolon. Megacolon may be seen as a primary disease, or it may arise following long-term constipation.

Clinical signs:

Affected pets usually strain, unsuccessfully, to defecate and may cry in pain while trying. Any faeces passed are hard and dry. The animal may also show signs of lethargy, reluctance to eat and vomiting.

How are constipation and megacolon diagnosed?

In most cases, a diagnosis of constipation can be made on the basis of the clinical signs your pet is showing. Further tests may be needed to establish the cause of the constipation. These may include x-rays of the abdomen and pelvis in order to look for pelvic injuries, colonic strictures or tumours. X-rays are also required for the diagnosis of megacolon.

Treatment protocols:

Initial treatment of a pet with constipation may involve administration of enemas and manual extraction of faeces at the hospital. The latter may necessitate an anaesthetic or sedative. Treatment of dehydration with intravenous fluids may also be needed in severely affected animals.

If the constipation recurs or becomes a long-term problem continuous therapy may be needed to prevent recurrence. A wide variety of treatments are available and the aim of these is to enable regular defecation of soft faeces. Altering the diet so that this contains more fibre (e.g., Metamucil) may be helpful, and lubricating laxatives or stool softeners may also be used in mildly affected animals.

More severely affected cats may need drugs that stimulate contraction of the colon. The doses of all of these drugs may need to be altered to produce the desired effect. Ideally, animals should defecate at least once every other day (most normal pets defecate once or twice a day depending on their diet).  Over a period of time, resistance to the treatment may be encountered, necessitating an increase in the drug dosage or a change to another therapy. No changes to the treatment protocol should be made without consulting your veterinary surgeon.

In long-haired cats regular grooming may reduce hair ingestion and reduce the likelihood of hairballs causing constipation.  Likewise treating any concurrent allergic skin disease, for example by flea control, is also vital. It is important to ensure there is always access to a clean litter tray so that frequent defecation is encouraged.

If megacolon develops, or if the constipation is severe and medical treatment is unsuccessful at controlling this, then surgery may be advisable. Surgical treatment involves removal of most of the colon which initially will result in diarrhoea since the colon is responsible for water removal from faeces. Over time this usually improves. The surgery should not result in loss of bowel control.

The long-term outlook varies tremendously according to the cause of the constipation, however, most patients can be adequately managed without having to resort to surgery, especially if medical therapy is implemented early.