Perineal Hernias in Dogs

Perineal hernias are relatively uncommon but are usually seen in un-castrated male dogs when they occur. Perineal hernias are caused by a weakened pelvic diaphragm, leading to symptoms like anal swelling, difficulty urinating and defecating, and abnormal tail carriage. Your vet will perform a rectal exam to diagnose a perineal hernia, followed by additional diagnostic tests like an ultrasound and blood analysis. Surgical removal of the hernia is usually very effective, and the prognosis is good for dogs in recovery. While you can't fully prevent perineal hernias, castration is the best means of protecting your dog. Boston terriers, boxers, Pekingese, and Welsh corgis are thought to be more prone to developing perineal hernias than other breeds.

What Are Perineal Hernias?

A perineal hernia is a hernia that results from a weakened or failed pelvic diaphragm—the muscular wall that supports the rectum. The hernia causes parts of the intestines or bladder to poke out through the perineal area, between the anus and, in male dogs, the scrotum. Perineal hernias are most commonly seen in older, un-castrated male dogs.

Symptoms of Perineal Hernias in Dogs

Perineal hernias in dogs are usually easily identifiable, marked by swelling around the anus. If you notice swelling, visit your vet right away.

The first sign of a perineal hernia is typically non-painful swelling on one or both sides of the dog's anus. Even though the hernia is non-painful, your dog will likely strain to defecate and urinate and experience some constipation, incontinence, and abdominal pain. Your dog will also likely position its tail abnormally to accommodate the swelling. Although rare, some dogs won't show symptoms other than anal swelling.

Causes of Perineal Hernias

The exact cause of perineal hernias is unknown, but there are various contributing factors.

• Castration status: Un-castrated male dogs are the demographic most prone to the development of perineal hernias. Un-castrated dogs often have enlarged prostates, putting excess pressure on the rectum when defecating or urinating. The rectal tissue weakens and tears, resulting in a perineal hernia. Female dogs can develop perineal hernias, but they are uncommon.
• Age: Most perineal hernias tend to occur in middle-aged to senior dogs. Dogs aged seven to nine are more likely to develop perineal hernias.
• Genetics: Certain dog breeds appear to be more impacted by perineal hernias than others. These breeds include the Boston terriers, boxer, Pekingese, and Welsh corgi. Additionally, some puppies may be born with congenital or inherited perineal hernias.
• Trauma: Trauma to the rectum, ranging from injury to tumors, can cause perineal hernias. Nerve damage caused by injury can lead a dog to unknowingly strain while defecating or urinating, increasing the likelihood of a perineal hernia.

Diagnosing Perineal Hernias in Dogs

To diagnose a perineal hernia, your vet will perform a thorough rectal examination on your dog. The exam will reveal whether the hernia is unilateral (on one side) or bilateral (both sides), the presence of any masses, or an enlarged prostate. If the prostate is enlarged, your vet will perform additional diagnostic tests to determine the cause. These tests may include an ultrasound, x-ray, blood analysis, and urinalysis. Some dogs may require sedation during a rectal exam. 

Treatment & Prevention

Surgery is the only curative treatment option for a perineal hernia. Severe perineal hernias may require emergency surgery, while minor hernias may be treated conservatively until a herniorrhaphy can be performed. Conservative treatment involves feeding your dog high-fiber, wet food and administering stool softeners. A veterinarian may need to remove impacted stool manually.

A herniorrhaphy surgery usually involves returning the contents of the abdominal cavity to the abdomen and repairing or replacing the pelvic diaphragm. The bladder and colon may be sutured to the abdominal wall to prevent recurring hernias. If the bladder is trapped in the hernia, the surgeon will insert a urinary catheter to empty the bladder. Prosthetic implants are sometimes used as part of the repair process. If the dog still has its testes, it will typically be neutered during the procedure to shrink the prostate and reduce the chance of recurrence.

The best preventative measure for perineal hernias is castration, as the condition rarely presents in neutered male dogs. Selective breeding may decrease the likelihood of perineal hernias in offspring; dogs with a history of perineal hernias should not be used for breeding.

Prognosis for Dogs With Perineal Hernias

Most dogs recover well following surgery for a perineal hernia, but complications can occur. Potential complications include infections and rectal prolapse, fecal incontinence, nerve damage, and rectal fistula, a hole or tunnel that connects the rectum to a nearby opening on the skin. Serious complications are rare, and most dogs will fully recover.

Post-operatively, keep your dog's incision clean and dry, and do not allow your dog to lick or chew the area. An e-collar (Elizabethan collar or "cone") will be necessary while your dog is healing.