Hernias in cats (perineal)
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.
What is a hernia?
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).
What is a perineal 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 faeces out from the rectum via the bottom (anus). If these muscles become weal or damaged, it becomes very hard for your cat to pass faeces. When straining is performed, to try and pass faeces, 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.
How will I know if my cat has a hernia?
You may notice a soft swelling besides your cat’s bottom (anus). This may bulge when your cat is trying to pass faeces and may vary in size at other times. Your cat may struggle to pass faeces, taking a long time and more straining than normal, passing small amounts more frequently, or becoming unable to pass faeces at all. If your cat is unable to pass faeces 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 faeces. 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.
How will my vet diagnose my cat’s hernia?
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 anaesthesia. Your vet 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.
How are perineal hernias treated?
Severe constipation is often present at the time of diagnosis of a perineal hernia. The first therapeutic step is to remove the impact faeces with gentle manipulation under sedation or anaesthesia and to then perform an enema to help to empty the backed-up faeces 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 faeces 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 fibre, than a very loose soft stool, and the use of an agent that modifies faecal 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 faeces. 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 faecal consistency for some time after the surgery, depending upon their progress.
How can I prevent my cat developing a hernia?
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.
What problems may occur after my cat’s hernia surgery?
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, however do not bathe the wound unless specifically directed to by a veterinary surgeon. 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 behaviours such as passing urine and faeces normally and having a good appetite. In particular following treatment of a perineal hernia there could be problems that occur with passing faeces or urine. Pleae notify your vet if any concerns arise. It is important to keep your cat's exercise restricted during the recovery phase, until your vet has completed a post-operative check and is happy with the healing.