Wilson's Perineal Hernia

Wilson is a 12 year old miniature fox terrier, who came to our Waiuku clinic with a swollen rear end, alongside his tail. The attending veterinaran recognised this to be a perineal hernia, and sent Wilson along to our Pukekohe hospital for surgical correction.

Perineal hernia is a difficult condition to understand due to the complicated anatomy involved. Essentially, there are muscular walls supporting the rectum, one on each side. These walls provide the strength and support that is required for the thin-walled rectum, while the support to the upper and lower sides is provided by the tail and the pelvis respectively.

Perineal hernia is when one or both of those muscular walls is weakened, and the rectum bulges out on that side, producing the visible swelling alongside the tail. When the muscular wall sags or tears, it allows organs from the abdomen to be pushed out through the pelvis and sit under the skin by the tail, which in time form adhesions and refuse to move back to where they came from.

There are several causes, but the most frequent is straining to pass faeces. In Wilson’s case, this was likely caused by his enlarged prostate gland, which is an extremely common problem in older male dogs.

Repair involves replacing everything from the abdomen where it should be, and then reconstructing a supportive wall somehow.

Wilson was found to be fit for surgery on pre-anaesthetic blood testing. Exploration of the hernia revealed it to contain a greatly enlarged prostate gland as well as some abdominal fat. Very careful dissection was followed by returning them back to the abdomen.

The supportive wall was then reconstructed using a muscular flap technique, which was helped enormously by having plenty of muscle present and not much fat.

Wilson never looked back and returned to normal with a new perineal wall. His owner reports that he is fully recovered & loving life.

What are the lessons from this sort of case?

• Bring in abnormal swellings early. This one was nice and early, so had not formed as many adhesions as will occur over a longer time, which will make the surgery much more difficult
• Castrate male dogs. Benign prostatic hypertrophy (enlargement) is a condition affecting 95% of male dogs from the age of about 9 years and will give difficulty passing faeces to many of them. It’s very easy to prevent, just castrate them before this age.
• Don’t cut tails off dogs. Lack of a tail to wag is thought to be a contributing factor to the weakening of the perineal muscular wall, which is why this hernia is often seen in dogs with docked tails. Added to that, performing surgery around this part of the body is made enormously more difficult if there is no tail to pull forwards when positioning them.

Nice case, good result. Very pleasing to have a completely fixable surgical problem in an older patient.

Paul Eason BVM&S MANZCVS