Perineal Hernia

What is a perineal hernia?

A perineal hernia occurs when the muscles of the perineum (the area between the anus and the scrotum or vulva that supports the organs of the pelvis) become weakened or torn. As a result, the bladder, intestines, or fat can push through the weakened muscles and bulge beneath the skin next to the anus. Perineal hernias are most common in middle-aged to older unneutered male dogs and rarely occur in female dogs or cats.

What are the  signs of a perineal hernia?

A perineal hernia may appear as swelling on either or both sides of your dog’s anus. Depending on how much tissue is herniated, it may even push the rectum to one side. The swelling is usually soft and can be reduced with pressure.

Dogs with perineal hernias often strain repeatedly as if trying to defecate. They may have difficulty passing stools and may become constipated. If the bladder has become herniated, they may also strain to urinate, have urinary incontinence, or be unable to urinate.

In severe cases, such as when part of the intestine has become trapped or if bladder herniation has caused a urinary obstruction, dogs will become lethargic and have a decreased appetite. Any compromise to the blood supply of the bladder or intestine could be life-threatening.

Why did my dog get a perineal hernia?

Perineal hernias can occur after trauma, but they are more commonly caused by gradual weakening of the muscles in the perineal area. The exact cause of this muscle weakness is not fully understood, but several factors may contribute:

• Hormones. Perineal hernias occur more commonly in unneutered male dogs, so hormones may play a role.
• Nerve damage. Disruption of nerves in the area, as can occur with spinal injuries, may weaken the muscles.             
• Excessive straining. Repeated straining to urinate or defecate may weaken the muscles over time and contribute to hernia development.

How are perineal hernias diagnosed?

Your veterinarian may suspect your dog has an inguinal hernia based on a physical examination. They may recommend several tests to confirm the diagnosis and look for other conditions that could affect treatment. These may include:

• Rectal examination. Your veterinarian may be able to feel the perineal hernia or an abnormal pocket in the rectum.
• Blood and urine tests. Baseline tests, including a complete blood count (CBC), serum biochemistry profile, and urinalysis, help rule out other medical conditions that could complicate treatment. They may also detect kidney abnormalities if the bladder has become trapped in the hernia and caused a urinary obstruction.
• Radiographs (X-rays) or ultrasound. These imaging tests help determine which organs or tissues have herniated through the weakened muscles. They can also help identify prostate disease or other conditions affecting the abdomen or pelvis.
• Hormonal testing. If your dog appears to be neutered but abdominal testicles are found on ultrasound, your veterinarian may recommend hormonal testing to determine whether your dog is truly neutered.

How are perineal hernias treated?

Generally, a perineal hernia does not require emergency treatment. However, if your dog becomes acutely ill because the bladder is trapped in the hernia and urine cannot pass normally (urinary obstruction), the bladder must be catheterized to allow normal urination. Your dog will also require supportive care, including intravenous fluids.

If constipation is severe, your dog may require manual removal of the feces while under sedation. Stool softeners and special diets can help reduce further episodes of constipation while waiting for surgery or if surgery cannot be performed. Any underlying causes of straining, such as prostate infection, should also be treated.

The most successful treatment for a perineal hernia is surgery to repair the weakened muscles. Simple hernias can often be repaired externally. More complicated hernias may require abdominal surgery to return the herniated organs to their normal position and secure them there. In severe cases, or if the hernia recurs, a surgical mesh implant may be used to support the surrounding muscles and strengthen the repair.

Neutering is recommended at the same time as hernia repair, along with treatment of any underlying causes of straining, to reduce the risk of recurrence. Dogs that are not neutered at the time of surgery are almost three times more likely to develop another perineal hernia. Because hernias often occur on both sides, a second surgery is usually required to repair the opposite side.

What is the prognosis?

With effective surgical intervention, the prognosis for a perineal hernia is very good. Although there is a risk of recurrence, controlling the straining and neutering of affected dogs significantly reduces this risk. Uncommon complications of surgery include infection and incision breakdown, fecal incontinence, and sciatic nerve compromise. Surgery can be technically challenging, so referral to a board-certified surgery specialist is often recommended.

If surgery cannot be performed, if surgery is unsuccessful, or if the underlying cause of straining cannot be treated, the prognosis may be more guarded.