Perineal Hernias

A hernia is the protrusion of an organ or tissue through an abnormal opening in the abdominal wall. A perineal hernia results from a weakening of the pelvic muscles that support the rectum which subsequently stretch and bulge with fat or abdominal tissue.

Perineal hernias are seen mostly in dogs and rarely cats or other species. The Boston Terrier, Boxer, Collie, Welsh Corgi, Pekingese, Dachshund, and Old English Sheepdog are the most commonly affected breeds. The vast majority of perineal hernia cases occur in middle aged or older intact males. In these dogs, testosterone causes a chronic enlargement (hypertrophy) of the prostate gland. As the animal strains to urinate and defecate around the enlarged prostate, the tissues adjacent to the rectum weaken, allowing fat or abdominal organs to push out around the rectum and form a pouch under the skin. This pouch may enlarge when straining pushes tissue out into it and it may become smaller as tissue moves back into the abdomen.

Females are rarely affected due to the greater strength, size, and area of the rectal attachments of the levator ani muscles as well as the absence of prostate glands. Approximately one third of perineal hernias are bilateral (occur on both sides).

Symptoms

The most common symptoms of perineal hernias are chronic constipation, straining to defecate, and a swelling on either side of the rectum. Other signs may include straining to urinate, pain on defecation, fecal incontinence, and altered tail carriage.

Diagnosis

A perineal hernia is diagnosed based on the history and physical examination. A defect in the pelvic diaphragm musculature or sacculation (outpouching) of the rectum are usually detected on rectal palpation. Fatty tissue is usually present in the hernia. A nonreducible (unmovable) fluid-filled mass in the hernia suggests displacement of the urinary bladder. In all cases, both sides of the pelvic diaphragm should be palpated. While the patient may appear to be unilaterally affected, both sides are often found to be weakened.

If the prostate is enlarged, the cause of this enlargement must be determined. Benign hyperplasia, abscessation, cyst formation, and tumors must all be considered and treated appropriately. Castration is recommended in all cases due to the effects of testosterone on the prostate gland and perianal musculature.

Treatment

Conservative therapy may be attempted in dogs with minimal signs or in those patients where the anesthetic risk is too great to consider surgery. Medical management is rarely successful in permanently controlling the clinical signs that are associated with perineal herniation.

These measures may also be used as an adjunct to surgical repair:

• Diet high in fiber and moisture content
• Stool softeners such as Metamucil
• Digital (manual) removal of impacted feces

Surgical repair is the treatment of choice for most cases of perineal hernias. This is achieved by suturing specific muscles together to reform a pelvic diaphragm. If there is insufficient tissue available to close the defect, an implanted surgical mesh may be used.

In those cases where the urinary bladder has retroflexed (flipped back) into the hernia, surgery should be performed immediately and the bladder repositioned into the abdomen. Abdominal surgery may be required to stabilize the bladder in its normal position.

Castration should be considered in all intact males due to the potential hormonal influence on perineal herniation. This is particularly important when the prostate is increased in size as enlargement of this gland may cause straining which will place unneeded stress on the surgical repair.

Postoperative Care

Antibiotic therapy is continued after surgery as the surgical site is considered contaminated due to its location. Stool softeners and a low residue diet are used for the first few weeks to minimize stress on the repair as the prostate shrinks in size and the chronic straining subsides. An Elizabethan collar is worn until the sutures are removed to prevent the patient from licking at the sutures.