Pet Factsheets

Hernias in cats (diaphragmatic)

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 in which tissues that should be within the abdomen bulge 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 diaphragmatic hernia?

A diaphragmatic hernia or rupture is when there are abdominal contents in the chest cavity that have passed through an opening or defect in the diaphragm, which is the muscle that separates the chest and the abdomen

A diaphragmatic rupture is much more common than a diaphragmatic hernia; it is caused by trauma, such as a blunt blow to the abdomen by a car accident or a fall, causing a tear in the diaphragm muscle. When the diaphragm tears, abdominal contents can pass into the chest compromising breathing. This is a true emergency and requires surgical repair once your vet has stabilised your pet. This injury can occur at any age if a significant trauma occurs. It is very difficult to judge if such any injury has occurred to your pet and this is why assessment by a vet is important if your pet has experienced a fall or hit by a car. Your vet will examine your pet and will recommend further tests (x-rays or ultrasound) if they have concerns on examination.  [Note that sometimes the term hernia is used for this type of injury, even though the problem has occurred due to a rupture of the diaphragm muscle.]

A true diaphragmatic hernia is an abnormality that your pet has been born with meaning that the diaphragm has not completely closed, therefore allowing some communication between the abdomen and the chest. This is rare and there are various forms, the most common form is a pericardial peritoneal diaphragmatic hernia (PPDH) in which the abdomen and the sac around the heart communicate. This can be serious but is also something your pet may live with and have a good quality of life. It may sometimes be picked up later on in life. If it is significant your kitten may have rapid breathing, poor exercise tolerance and may have some vomiting. A diagnosis can be made by chest x-ray. This type of hernia is not always treated with surgery; it may be best left untreated if it is not causing obvious signs and has only been picked up when performing another check.  

What is a hiatal hernia?

This type of hernia results from the protrusion of abdominal organs through the oesophageal hiatus (hole via which the oesophagus passes from the chest into the abdomen to join the stomach) of the diaphragm into the thoracic cavity, which means that the abdominal organs can move alongside the oesophagus and into the chest. Affected cats may regurgitate their food and they are also at high risk of developing pneumonia. Typically the hernia moves back and fore with breathing and there is only a small portion of the stomach entering into the chest; the main issue is due to the effect this has on the area allowing stomach acid to damage the lining of the oesophagus. Occasionally however other organs such as small intestine or spleen can herniate. This is a very uncommon condition in the cat.

How will I know if my cat has a hernia?

With a traumatic diaphragmatic hernia the most common clinical sign will be an increase in breathing rate or difficulty breathing. If the diaphragmatic hernia becomes very severe, with lots of organs herniated, in particular the stomach, then your cat may go into shock and collapse. Other injuries, such as a cut on a limb or scuffed nails, may be the only thing you note on first inspection, alerting you to the sign that a trauma event has occurred. For a PPDH the signs may be respiratory, such as an increase in breathing rate. There may also be low grade gastrointestinal signs, such as occasional vomiting.

A hiatal hernia leads to reflux of gastric acid and can be seen as regurgitation (bringing up liquid or food from the stomach in a passive way) or reflux (frequent lip licking and swallowing). This is a very uncommon in the cat.

How will my vet diagnose my cat’s hernia?

If your vet has a clinical suspicion of a diaphragmatic, PPDH or hiatal hernia the first stage of achieving a diagnosis would be to obtain images of the chest and abdomen with x-rays of computed tomography (CT).

The diagnosis of a hiatal hernia can be challenging as the position of the stomach moves and therefore it is only evident if the image is captured at the correct moment. The use of fluoroscopy (an x-ray movie) allows this to be assessed more thoroughly whilst feeding the cat a wet paste like food containing barium. It would be necessary for the cat to be sitting in a box whilst this was done. This examination may be challenging to achieve due to a cat’s reluctance to eat in an unfamiliar situation.

How are hernias treated?

Surgery upon the diaphragm is typically performed from an abdominal surgical approach, which allows the surgeon to replace any herniated abdominal organs, check them for injury and repair the diaphragm. Repair of a diaphragmatic hernia requires the chest to be drained of air at the end of the surgery, so that they can regain control of their own breathing (this is done by the anaesthetist during the surgery). This can be done by placing a small tube across the diaphragm as it is closed and draining the air via this route, or placing a chest drain between the ribs into the chest if longer term drainage is anticipated (this would tend to be for long standing hernias). For PPDH surgery,  the abdominal contents are withdrawn into the abdomen and the defect in the diaphragm is closed. The pleural space is not typically entered and therefore the chest should not need to be drained.

Hiatal hernias are addressed by narrowing the opening of the diaphragmatic hiatus through which the oesophagus passes. The stomach is also secured within the abdomen using a feeding tube; this tube can be used to provide extra nutrition during recovery (if surgery is required then the cat may have had inadequate nutrition). This is a very rare condition in the cat and the primary focus may be looking for and treating causes of increased negative intrathoracic pressure, such as upper respiratory tract obstruction that may have caused this.

How can I prevent my cat having a hernia?

These types of hernias cannot be prevented in the individual and either occur due to unfortunate developmental events meaning they are born with the abnormality or that they have suffered a traumatic event. Sometimes a trauma may occur and not be noted by the owner as cats can tend to hide things; the diaphragmatic hernia/rupture may be noted further down the line.

Cats that have been diagnosed with a PPDH should not be bred from as there may be a genetic basis.

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 any of these are noted please speak to your veterinary surgeon for advice.

The wound itself should be left open to the air and should be kept clean and dry, however do not bathe the wound unless specifically directed by a veterinary surgeon. Often making the wound moist can increase the risk of a wound 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.

Monitor your cat for normal behaviours such as passing urine and faeces normally and having a good appetite. Please pay particular attention to your cat’s breathing. It can be helpful to note how many breaths they take per minute (noted by the chest rising); this is best done when they are sleeping. Any breathing in which your cat opens their mouth with each breath shows they are in a serious condition and are experiencing respiratory distress. Try to stay calm and arrange to see your vet as an emergency. If you observe this it could be because the internal healing has failed and the abdominal contents have moved into the chest, or it is also possible that your cat has developed a serious infection within the chest cavity post-operatively.

If your cat has a cough and seems unwell please speak to your vet. It is quite common for a slight dry cough to be present for a couple of days following the anaesthetic due to the endotracheal tube causing irritation and this should not be of much concern and will self-resolve. A moist cough is suggestive of pneumonia, which can occur following any anaesthetic but is more likely if there is another predisposing factor, such as regurgitation which occurs in hiatal hernia. 

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. Your cat must be restricted to the house for 6 weeks and to a single room for 2 weeks. If your cat is inclined to jump, run or climb then use of a crate is sensible to ensure proper rest. This should have enough space for a bed, water and food area and a litter tray.