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Diaphragmatic hernia

The diaphragm is the muscular separation between the chest and abdominal cavities. The diaphragm keeps thoracic and abdominal organs separate as well as aiding respiration.

Ruptures in the diaphragm allow abdominal organs to migrate into the chest cavity, effectively ‘squashing’ the lungs and compromising their capacity to expand during breathing. This break in the diaphragm - called a diaphragmatic hernia – can be the result of trauma such as a car accident or, more rarely, the hernia can be congenital. Sometimes the trauma has happened days, weeks or even months before the intestine or other organs find the tear and enter the chest, causing sudden respiratory distress.

CVH vets diagnose and treat diaphragmatic hernias quite commonly in dogs and cats. Billie – a wonderfully loveable and much-loved Wolfhound cross pup – was presented to Crookwell Veterinary Hospital at 14 weeks of age with increasing respiratory distress and a history of vomiting. X-rays (see below) showed a mass in the chest cavity and, with his other clinical signs, a diagnosis of diaphragmatic hernia was made. Given his age, there were concerns the hernia was congenital (often requiring specialist surgery to repair) but Billie’s owners asked our vets to undertake the surgery.

Billie’s hernia was large enough for the liver and stomach to have migrated into the chest cavity. Not only was this large mass constricting the lungs causing breathing difficulties, the displacement of the liver and stomach was initiating vomiting whenever Billie tried to eat.

Billie made a full recovery after his operation. On reflection, his owners had noticed that Billie had suddenly refused to visit the horse paddock – it’s highly likely the hernia was the result of a kick from one of their ponies.


Pets with diaphragmatic hernias are almost always presented with laboured breathing. They often have a rapid, shallow breathing pattern and sometimes will adopt an abnormal breathing posture – what we call dog-sitting – because when they lie down, the organs may slide further into the chest making it even harder for them to breathe.

 X-rays of the chest show the normally distinct line of the diaphragm has disappeared. Depending on which organs have moved into the chest, there may be an obvious mass (as with Billie’s liver) or it’s possible to see a gas-filled stomach and/or intestines. Contrast radiography with barium is sometimes used to confirm the intestines and/or stomach are sitting within the thoracic cavity.

Images below: image on the left shows a normal chest with an unbroken diaphragmatic line, clear silhouette of the heart and air-filled lungs. The image to the right shows Billie’s x-ray with the mass of the liver and stomach in the chest cavity.










The only treatment for a diaphragmatic hernia is surgery. Before surgery, the pet must be treated for shock (if the trauma has just happened) and breathing and heart rate stabilised.

Surgery can be challenging and difficult, depending on the extent of the tear in the diaphragm, adhesions that may have formed if the hernia was longstanding, and the fact that any surgery involving opening the thorax requires skillful anaesthesia – once opened, the thorax is no longer a vacuum and the lungs immediately collapse. The vets and vet nurses managing the anaesthesia must ‘breathe’ for the animal the entire duration of surgery to ensure oxygen continues to flow into the lungs and enter the circulation.

Once the hernia is almost fully repaired and closed, the anaesthesia becomes even more delicate. The lungs must be expanded by a squeeze of the oxygen bag at the exact moment the last suture closes the chest cavity. The amount of oxygen delivered is critical – too much and the anaesthetist risks rupturing lung cells, too little and the lungs don’t expand to full capacity.

Follow up to surgery

The repair of a diaphragmatic hernia involves major surgery. Pets need at least several days of intensive monitoring and pain management, rest, and treatment for any other injuries sustained if there has been a traumatic incident. Once over the initial stages of recovery, the pet can go home on strict rest and monitoring.

The prognosis for pets with a traumatic diaphragmatic hernia varies depending on other injuries sustained at the time, and the degree of adhesions if the hernia is longstanding. Most pets that recover successfully from surgery will regain full health.