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 in dogs, and rarely cats and 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 the middle aged to 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 may be 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 their levator ani muscles (one of the pelvic muscles) and their lack of a prostate gland. Approximately one third of the hernias are bilateral (occurring on both sides).
The most common owner complaints of dogs with 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.
The hernia is diagnosed based on the history and physical examination. A defect in the pelvic diaphragm musculature or sacculation (out pouching) of the rectum are usually detected on rectal palpation. Fatty tissue is usually present in the hernia. A non-reducible (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 times 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.
Conservative Therapy may be tried to palliate 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:
Surgical Repair is the treatment of choice for most cases of perineal hernia. 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.
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 suture line.
Copyright 1998, Southern
California Veterinary Surgical Group