Perineal Hernia – Viewer discretion is advised!

Perineal Hernia – Viewer discretion is advised!

May 1, 2014

From the desk of Dr. Voorheis


For days now, I have been working on this week’s blog and intended a focus on all facets of renal disease beginning with an explanation of what the kidney does, what goes wrong in acute renal failure, and what goes wrong in the more common chronic renal failure. This was to be followed with information on treatment of both conditions. So, how did I jump from renal function and disease to perineal hernias?  Well, there is a very special dog in the hospital at the moment who brought us to this topic today. His condition and surgery took a great deal of my writing time, so I decided to dedicate this week’s blog to him instead.  Like I’ve said before, the critters come first. And second, third and forth for that matter. So, this will be a short one.

Before I get into this topic though, I will let you know that a thorough topic on the kidneys is coming. After all, any organ that gets 20% of the blood flow directly from the heart has got to be pretty important! Now one disclaimer as my title indicates – pictures in this blog are graphic, so readers beware.


Perineal hernias occur when the muscles of the perineum separate, allowing the rectum, pelvic or abdominal contents to displace perineal skin. This occurs when the muscles of the pelvic diaphragm fail to support the wall of the rectum, allowing persistent rectal distension and impaired defecation. This condition is most commonly seen in “intact” (un-neutered) male dogs. The causes of perineal herniation are poorly understood but it is known to be associated with male hormones, straining (to defecate) and congenital or acquired muscle weakness or atrophy. The pelvic diaphragm is stronger in female dogs. In some cases this muscle weakness is associated with other nerve weakness as well. Other conditions that seem to predispose the animal to perineal herniation include prostatitis, bladder infections, urinary tract obstructions, colorectal obstructions, rectal deviation, perianal inflammation, anal sac inflammation and diarrhea or constipation. In other words, anything that causes additional straining or pushing of those pelvic muscles can cause them to herniate.

Herniation can be unilateral or bilateral which means on one side or on both sides. The hernias occur between the levator ani, external anal sphincter and internal obturator muscles. They can occur between the sacrotuberous ligament and the coccygeal muscles. There are other muscle groups that can be affected as well.  Is your head spinning yet?

The hernia may contain pelvic or retroperitoneal fat, deviated or dilated rectum, a rectal diverticulum, prostate, or urinary bladder, or small bowel. Organs that become displaced into the hernia may become obstructed or strangulated. This can be associated with rapid decline of the animal, who may have had the condition for several months before the negative outcome arises. Sometimes, the retroperitoneal fat that is in the hernia changes over time and becomes thickened. Sometimes these contents adhere themselves to the wall of the rectum and that tissue has to be broken down for the hernia to be repaired.

So you might be wondering how you would know if your dog (or cat) has a perineal hernia. Well, most of these critters are older, intact male dogs. About 93% of affected animals fall into that category. The condition is rare in female dogs and even more rare in cats. Most owners will bring the dog to see the vet because the dog for is having trouble defecating. Sometimes the owners will notice a swelling lateral to the anus. Again, photos are quite graphic:

Hernia1 Hernia2

Occasionally these animals present as emergencies due to bladder or intestinal entrapment which is not good. The diagnosis is most often made by a rectal examination. Radiographs can be utilized to visualize bladder entrapment and sometimes contrast is used to document that condition. The veterinarian must consider some other causes for perineal swelling such as perianal cancer, perianal gland hyperplasia, anal sac disease or infection or anal sac cancer.

Most often, this is a surgically correctable disease. Occasionally, we treat conservatively with stool softeners, enemas, dietary changes and manual rectal evacuation. But surgery is usually recommended in these cases. We also generally recommend castration at the same time as castrated dogs have a recurrence rate nearly 3 times less than non castrated dogs. When the herniation is bilateral, the hernias are often repaired one at a time.  For those unfortunate dogs with bilateral disease, they are usually repaired in two procedures. Sometimes we repair both sides at the same time with a one to two month time frame in between procedures, but that is not the norm.

Infection is common with this type of surgery, so close attention must be paid after surgery to increase the chance of success.  The most common surgical complications can include infection, fecal incontinence, recurrence, and full or partial paralysis of the nerve endings surrounding the surgical site.

A word about prevention; this disease is extremely rare in neutered dogs. Full castration is certainly a preventative measure. No other means of prevention are currently known.

Well, as I said….this was a short one. I’m headed back in to surgery!

Until next week,

Dr. Voorheis

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