Perineal hernias

There are several types of hernia (also known as a rupture) seen in the cat 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.

©Dick White

A hernia is a swelling caused by structures from the abdomen bulging out through the muscle wall. This may be through a natural opening, which is meant to be there but has become a larger opening than normal, or a gap that has developed; this can occur due to old-age or due to 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 from the omentum, a fatty membrane which lies within the abdomen, but abdominal organs could be present.

There are other hernias that occur between the muscle layers internally and so you cannot see any swelling when looking at your cat but may have noticed signs of illness (bringing up food/regurgitating for hiatal hernia) or rapid or difficulty breathing (diaphragmatic hernia).

Perineal hernias are fairly uncommon in the cat, in particular when compared to the dog where it is seen in middle 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). If these muscles become weal or damaged, it becomes very hard for your cat to pass feces. When straining is performed, to try and pass feces, it is not effective and instead the area around the bottom (perineum) may be seen to bulge. There may be a permanent swelling beside the bottom where contents from the abdomen have been pushed out through the weakness in the muscle. This is most often omentum (fat) but can sometimes contain the prostate and bladder which can become very serious. If you are awaiting treatment for perineal hernia and your cat has difficulty passing urine too then please seek urgent veterinary advice.

You may notice a soft swelling besides your cat’s bottom (anus). This may bulge when your cat is trying to pass feces and may vary in size at other times. Your cat may struggle to pass feces, taking a long time and more straining than normal, passing small amounts more frequently, or becoming unable to pass feces at all. If your cat is unable to pass feces they will become unwell and may vomit and lose their appetite. Perineal hernia is a rare condition in the cat and can be difficult to diagnose because of cat’s private nature when toileting. Urinary tract issues (cystitis and bladder stones) are a far more common diagnosis in the cat and it is not uncommon for the initial clinical suspicion to be that there are problems with urinating rather than passing feces. This is made more complicated by the fact that, in the cat, the underlying cause of the hernia developing can be repeated  straining from urinary tract problems.

The diagnosis of a perineal hernia is made by examination of the rectum with gentle digital examination. Due to a cat’s small size this must be performed under sedation or general anesthesia. Your veterinarian will be feeling for a weakness in the muscle layer to the side of the rectum. Diagnostic imaging: x-ray or ultrasound of the abdomen and the perineum (cat’s bottom area) may be helpful to further assess what is involved in the hernia. Further investigations may also be performed to try to identify another cause for straining, leading to the hernia, in particular assessment of the urinary tract, which may be performed by ultrasound or require contrast studies (dye which appears on an x-ray) in some cases.

Severe constipation is often present at the time of diagnosis of a perineal hernia. The first therapeutic step is to remove the impact feces with gentle manipulation under sedation or anesthesia and to then perform an enema to help to empty the backed-up feces in the colon. Once the blockage has been removed, various strategies can be used to achieve medical management as a palliative approach, or before or after surgery has been performed. Lactulose is a laxative that makes the feces more liquid and reduces the risk of further blockages. Once surgery has been performed it is better to have a formed stool that contains adequate fiber, than a very loose soft stool, and the use of an agent that modifies fecal consistency, such as Peridale granules (Sterculia) in food. Liquid paraffin is best avoided if other therapies are effective, as it can be difficult to administer and causes the risk of pneumonia if swallowed down the wrong way.

Surgery to treat a perineal hernia involves making a surgical wound alongside your cat’s bottom (anus) and then using one of the muscles between the hip and the pelvis to repair the gap in the layer of muscles, thereby providing support when your cat passes feces. This muscle can be used safely as there are a number of other muscles that have the same function. Your cat will need some attention to diet and the use of agents that modify fecal consistency for some time after the surgery, depending upon their progress.

In many cases there is no specific action that will prevent this problem arising. However keeping your cat in healthy, fit condition can reduce the risks as being overweight can predispose to some hernias in older age. Being aware of your cat’s toilet habits can help to pick up on a problem sooner rather than later and reduce the severity of the condition.

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 veterinarian for advice.

The wound itself is left open to the air after surgery and should be kept clean and dry, however do not bathe the wound unless specifically directed to by a veterinarian. Often making the wound moist can increase the risk of infection. Your cat, and other pets, should be prevented from interfering with the wound. Please use a buster collar, post-op coat or T-Shirt to prevent interference and keep other pets separate when not supervising interactions.

Please monitor your cat for normal behaviors such as passing urine and feces normally and having a good appetite. In particular following treatment of a perineal hernia there could be problems that occur with passing feces or urine. Please notify your veterinarian if any concerns arise. It is important to keep your cat’s exercise restricted during the recovery phase, until your veterinarian has completed a post-operative check and is happy with the healing.