The diaphragm is a thin muscle that separates the organs in the chest (heart, lungs) from the organs in the abdomen. It is also involved in breathing: when the diaphragm contracts, it helps pull air into the lungs.

A hernia develops when an organ pushes through a weak spot in the muscle around it, creating a hole.

Diaphragmatic hernias result from abdominal organs (e.g. liver, stomach, intestines) being pushed through a hole in the diaphragm. That hole is the hernia. The hole can be caused by trauma, such as being hit by a car, or it can be congenital, meaning that the pet was born with it.

Peritoneopericardial Diaphragmatic Hernia

A certain type of defect that has a big name - peritoneopericardial diaphragmatic hernia - is not nearly as complicated as it sounds. As we know, the diaphragm is a muscle that runs between the chest and abdomen. It helps us breathe by affecting the communication between the double-walled sac that contains the heart and the membrane that lines the belly. The heart sac is called the pericardium and the membrane is called the peritoneum. What happens with this type of hernia is that abdominal organs can move through the hole in the diaphragm directly into the heart sac. Obviously, abdominal organs are not supposed to be in the heart sac. Usually cats and dogs are born with this type of hernia, but trauma can also cause it.

Diaphragmatic Hernia Symptoms

When the abdominal organs have moved through the hole in the diaphragm, they become trapped and lose their blood supply. Misplaced organs in the chest can also crowd the lungs, or in the case of peritoneopericardial diaphragmatic hernias they can crowd the heart, preventing pets from breathing normally or letting the heartbeat correctly. Symptoms can include coughing, poor appetite, laying around more, trouble breathing or taking rapid and short breaths, fever, and collapse. In some cases, pets can live for many years without any symptoms, especially if the abdominal organs are able to move easily in and out of the chest or the hole is too small to allow movement through it. Such hernias may be found unexpectedly while addressing another problem.

Diagnosing a Hernia

For diagnosis, the veterinarian will perform a thorough physical examination. Sometimes a veterinarian will become suspicious when they hear tummy grumbles in the chest instead of in the belly. X-rays of hernias often show abdominal contents in the chest, or unusual gas patterns or shadows. If the X-rays don’t show an obvious answer, the veterinarian may give an ultrasound or they may choose a barium series, in which they feed the pet a type of medicine called barium to highlight the stomach and intestines on additional X-rays.

Treatment

Treatment requires surgery to fix the hole in the diaphragm (and heart for peritoneopericardial diaphragmatic hernias) and move the abdominal organs back into the belly. If the organs are severely damaged from being trapped in the chest, surgery to fix the damage or remove the entire organ may also be necessary. 

Unfortunately, diaphragmatic hernia repair carries some risk because the diaphragm helps us breathe. Because of this risk, some veterinarians will avoid surgery in pets that do not show symptoms. The issue with waiting until symptoms occur to perform a risky surgery means that organ damage may be irreparable by the time surgery is performed, so it is important to fully discuss the pros and cons of a wait-and-see approach with your veterinarian. 

For pets that do undergo surgical repair, once the pet has fully recovered and healed from surgery, they are unlikely to experience future issues.