A hernia is an abnormal opening through which an organ or tissue protrudes. A perineal hernia (PAH) results from a weakening of the muscles that support the rectum (pelvic diaphragm). These hernias begin to bulge when they fill with fat, abdominal tissue, or the urinary bladder, or when part of the rectum slides into the pocket.

What are the causes?

There are a number of possible causes for perineal hernias. It is believed that intact male dogs, due to their often enlarged prostate, exert more pressure when urinating and defecating, and the tissues around the rectum eventually stretch, weaken and then tear, resulting in a perineal hernia. Some veterinarians also speculate that hormonal differences in intact male dogs predispose to perineal hernias; as such, hernias are far less common in castrated dogs.

Which breeds are predisposed and what are the symptoms?

Perineal hernias are most common in middle-aged and geriatric intact male dogs and are rarely seen in cats. The breeds that are most commonly affected are Boston Terriers, Boxers, Welsh Corgis, Pekingese, and Dachshunds. When a perineal hernia occurs in a cat it can be a primary problem or secondary problem associated with megacolon. Megacolon is a condition where the colon becomes dilated and causes constipation and straining and should be considered in all cats that have a perineal hernia. More than 30 percent of perineal hernias occur on both sides of the rectum.

The most common symptoms of a perineal hernia are swelling beside the rectum, constipation, and straining to defecate. Other symptoms are painful defecation, fecal incontinence, altered tail carriage, and straining to urinate.

How is it diagnosed?

Diagnosis is based on history and physical examination. A rectal examination and palpation is necessary to assess the pelvic diaphragm musculature. If the rectal examination reveals an enlarged prostate, a cause must be determined. Benign hyperplasia (enlargement), tumor, abscess, and prostatic or paraprostatic cysts must be considered, and additional diagnostics, such as ultrasound, may be indicated in order to treat the underlying cause.

What are the treatment options?

If the clinical signs associated with a perineal hernia (PAH) are minimal, conservative treatment is an option but is rarely successful in controlling the clinical signs long term. Conservative therapy would include a high fiber/moist diet, stool softeners, and manual removal of impacted feces.

Surgery is the treatment of choice. As indicated above, hormonal changes in the older intact dog have been shown to be associated with development of PAH. As such, castration is necessary for all intact males because of the testosterone influence on the prostate and perianal musculature—without castration, PAH will recur.

During repair of the PAH, specific muscles of the pelvic diaphragm are sutured together to repair the defect. Frequently, the repair is re-enforced with a local muscle flap. Surgical mesh may be utilized in cases where there is not enough tissue to close the defect. In cases where the urinary bladder has slipped through the defect, an additional abdominal procedure may be needed to stabilize the bladder.

It has been shown that staging the surgery with an abdominal procedure first, which allows movement of the rectum and urinary bladder cranially (towards the head of the dog), followed by the actual hernia repair, improves overall success rates. This approach is preferred by certain surgeons. In the hands of an experienced surgeon, this technique is associated with a success rate of greater than 90 percent.

What is the post-operative care?

The surgical area, next to the rectum, and under the tail needs to be kept clean and dry. A course of antibiotics will be dispensed due to the contamination factor in surgeries performed near the rectum. Stool softeners, such as Metamucil or canned diet and a low residue diet are suggested for several weeks to try and prevent straining. The most common complications are reoccurrence of the hernia and infection of the surgical site.

Frequently Asked Questions:

How long will my pet need to stay in the hospital?

Generally, pets will stay the night after the procedure and be discharged the following day.

Is castration necessary?

Yes. Perineal hernias are only found in intact males and castration will reduce the size of the prostate and remove the hormonal influence. Most veterinarians consider castration necessary, as the recurrence rate is much higher if the animal is not castrated.

What is considered an emergency?

Occasionally, the bladder can become stuck in the hernia, meaning the pet cannot urinate. Similarly, intestine can become entrapped in the hernia, leading to strangulation of the bowel. Either of these scenarios necessitates immediate veterinary attention.