Perineal hernias

There are several types of hernia (also known as a rupture) seen in the dog and the causes vary between the different types. Some hernias can be minor, but in certain circumstances they can be very serious and often require surgical treatment.

A hernia is a swelling caused by structures from the abdomen bulging out through the muscle wall. The structures may escape by stretching a natural opening such as in an umbilical hernia, or come through a defect in the muscle wall that has developed due to old-age or trauma. The swelling may appear as a lump under the skin on the abdomen (umbilical, inguinal) or beside the anus (perineal). Typically, the swelling contains some fatty tissue but, in some cases, abdominal organs (most commonly sections of bowel) could be present.

Sometimes hernias form between the deeper muscle layers so the swelling is not obvious when looking from the outside. These may go unrecognized until your dog becomes unwell due to entrapment of a vital structure. Signs could include bringing up food/regurgitating for hiatal hernias or rapid or difficulty breathing with diaphragmatic hernias.

Perineal hernias occur almost exclusively in middle-aged to older male entire dogs. In a perineal hernia the swelling occurs between the muscles surrounding the bottom. The function of these muscles is to provide firm backwards pressure when the abdominal muscles contract to force feces out from the rectum via the bottom (anus). These muscles can become weakened due to the effects of testosterone and this can make it very hard for your dog to pass feces. When your dog squats and strains the area around the bottom (perineum) may start to bulge. As the disease progresses, tissues from the abdomen may get pushed between the muscle layers during straining and a permanent swelling can develop beside the bottom. The swelling usually contains fat but sometimes the prostate or bladder can become trapped and this is very serious. If this happens your dog may be unable to pass urine. If your dog has a perineal hernia and has any urinary signs you should seek urgent veterinary advice.

Most owners seek veterinary advice for a perineal hernia because they notice their dog is having difficulties passing motions. Often this is straining without production of feces or passing small pieces of faeces on multiple occasions rather than just in one go. If your dog has trouble passing feces they will be uncomfortable and may develop a firm swelling next to their bottom associated with an unpleasant smell.

The characteristic soft and non-painful swelling in a classic location may make your veterinarian suspicious of a perineal hernia. Your vet may be able to distinguish a hernia from other forms of swellings, such as an abscess or a tumor, by the appearance and feel of the mass when they examine your dog. The diagnosis of a perineal hernia requires a rectal examination. Your veterinarian will gently insert a gloved finger into your dog’s bottom so that they can feel if the muscle of the perineum is intact. Further tests to confirm the diagnosis include x-rays of the abdomen and also possibly an ultrasound. In some circumstances a Computed Tomography (CT) scan may be chosen if additional information is considered beneficial.

If a non-painful soft hernia becomes painful and firmer you must seek urgent veterinary attention for your dog. This change could suggest inflammation and may mean that an internal organ has become twisted within the hernia. If this happens the tissue may lose its blood supply and start to die. If the bladder becomes trapped in the hernia and urine cannot be passed – this is a life-threatening emergency.

If dogs have clinical signs then surgical treatment to correct the perineal hernia is advisable to avoid the risk of the condition worsening and serious complications developing. Surgery requires a general anesthetic and the area of the swelling, alongside your dog’s bottom, is opened to allow the contents within the swelling to be pushed back into the abdomen. The opening between the muscles of the perineum is then closed. Sometimes the abdomen will also need to be opened through a separate wound so that your veterinarian can check the organs within the abdomen more thoroughly, or to stabilize the bladder in the abdomen to reduce the risk of recurrence.

In many cases there is no specific action that will prevent this problem arising. However overweight dogs are known to be more prone to hernias so keeping your dog in a healthy, fit body condition can reduce the risks. Entire dogs have a far higher risk of developing a hernia later in life because of the effects of testosterone on weakening muscles. If your dog is diagnosed with a perineal hernia it is essential that castration is performed as part of the treatment; without castration the rate of recurrence is high.

There is a risk with any surgery of bleeding, wound infection and wound breakdown. With a hernia there is also the risk of recurrence. It is important to monitor for signs of bleeding, swelling of the area around the wound, recurrence of swelling beneath the wound and wound discharge. If you see any of these signs please speak to your veterinary surgeon for advice.

The wound itself is left open to the air after surgery and should be kept clean and dry. If you are concerned that the wound is dirty contact your veterinarian before bathing the wound as the risk of infection is higher if the wound is wet. Your dog, and other pets, should be prevented from interfering with the wound. You must use a buster collar, post-op coat or T-Shirt to prevent interference and keep other pets away from your dog when you are not supervising interactions.

After surgery you should watch your dog closely to see that they are showing normal behaviors such as passing urine and feces normally and have a good appetite. Let your veterinarian know if you have any concerns. After a perineal hernia repair your dog may have a much better ability to push when straining to pass faeces and this can, on rare occasions, result in the rectum itself being passed. If this happens it can be very alarming and so your veterinarian may want to keep your dog in hospital until it has passed feces normally. If your dog did prolapse some rectal tissue you should cover the exposed tissues with a wet tea towel (or another lint-free cloth) to minimise trauma and keep it moist and get them immediately to a veterinary hospital. It is really important that your dog does not lick at their bottom if this has happened as they can easily traumatise the rectal tissue which can be very serious.

Your dog’s exercise should be restricted during the recovery phase, until your veterinarian has completed a post-operative check and is happy with the healing. Your dog must remain on the lead at all times for the first 10 days, even when taken to the garden for toilet purposes. Your veterinarian will give you specific instructions regarding the return to normal level of exercise; typically on lead exercise must continue for a further 4 weeks with a gradual increases in length of walk each day.

There remains a risk of recurrence following perineal hernia, because the muscles in the area are already weak. Dogs should be castrated at the time of surgery (if they are entire) to reduce the risk of further weakening of the muscle but muscle weakness is not likely to reverse and the hernia may recur. If the hernia does recur a second operation may be possible – in this case a large muscle flap may be taken from the leg to strengthen the site. This does not affect your dog’s ability to walk but does provide a more robust muscle repair.

It is important to also make changes to the diet to help your dog pass feces easily. Fibre supplementation (eg Peridale granules or Fibogel) in the food will help with fecal consistency.