Perineal Hernia in Dogs

By Alex Gallagher , DVM, MS, DACVIM (SAIM), University of Florida

Last full review/revision Oct 2020 | Content last modified Oct 2020

Perineal hernia results from failure of the levator ani and coccygeal muscles, leading to herniation of pelvic or abdominal viscera. Signs may include perineal swelling, constipation, tenesmus, and dysuria. Diagnosis is based on history and physical examination, and radiography or ultrasonography may help confirm which tissues are herniated. Surgical correction is the primary treatment, but there is a high chance of recurrence or complications.

Perineal hernia is a failure of the levator ani and coccygeus muscles, resulting in herniation of pelvic and/or abdominal viscera into the perineum. Perineal hernias occur most often in middle-aged to older male, intact dogs. They often occur in mixed-breed dogs, but breed predispositions have been reported in Welsh Corgis, Boston Terriers, Boxers, Collies, Kelpies, Dachshunds, Miniature Poodles, Old English Sheepdogs, and Pekingese.

Etiology and Pathogenesis

Many factors are involved, including breed predisposition, hormonal imbalance, prostatic disease, chronic constipation, and weakness of the pelvic diaphragm due to chronic straining. The higher incidence among sexually intact males is evidence that hormonal influences probably play a primary role. Prostatic hypertrophy attributed to sex-hormone imbalance has been strongly implicated. Both estrogens and androgens have been cited as causative agents.

Clinical Findings

The primary clinical findings of perineal hernia in dogs are:

perineal swelling, which is usually nonpainful
constipation or obstipation
tenesmus
dyschezia
stranguria/dysuria

Diagnosis

Based on history and physical examination

Diagnosis of perineal hernia in dogs is based on the history and physical examination, with a key finding a perineal swelling that is fluctuant and reducible. Rectal examination will reveal unilateral or bilateral weakness of the pelvic diaphragm with deviation of the rectal wall toward the side of herniation (unilateral) or dilation of the rectum (bilateral). A firm mass associated with bladder herniation may also be palpable. Abdominal radiographs may reveal fecal distension of the rectum, increased soft tissue in the perineum due to bladder herniation, or herniated, gas-filled bowel loops. Perineal ultrasonography can be used to determine whether the prostate, urinary bladder, or bowel loops are present within the hernia.

Treatment

Surgical correction is the primary treatment

Perineal hernia is uncommonly an emergency, except when the bladder has herniated, resulting in urinary obstruction, or when a loop of intestine is strangulated, resulting in ischemia. If catheterization cannot be done, the urine should be removed by cystocentesis and an attempt made to reduce the hernia. An indwelling urinary catheter may be necessary to ensure urethral patency and prevent recurrence of obstruction.

Surgical correction is always indicated, and concurrent castration to reduce recurrence is recommended. The prognosis is guarded because of the high incidence of recurrence (10%–46%) and postoperative complications such as infection, rectocutaneous fistula, anal sac fistula, sciatic and pudendal nerve entrapment, and rectal prolapse.

Key Points

Perineal hernia is an uncommon disease that most often effects middle-aged to older male, intact dogs.
Diagnosis is based on consistent clinical signs and rectal palpation. Dogs may present emergently due to urinary obstruction secondary to bladder herniation.
Surgical correction is the primary treatment, but herniation can recur in 10%–46% of dogs

Source: MERCK MANUAL Veterinary Manual