The large muscle which separates the chest and lungs from the liver and other abdominal organs is called the diaphragm. As the diaphragm contracts and relaxes, it enlarges and compresses the chest cavity. This forces air to move in and out of the lungs. Breathing depends largely on the function of the diaphragm.
Types of diaphragmatic hernias
Acquired Diaphragmatic Hernia:
An acquired diaphragmatic hernia is a rupture of the diaphragmatic muscle. This is the result of trauma to a cat such as a severe fall or blow to the abdomen. As the abdominal contents such as the stomach and liver are forced against the diaphragm, a tear or rupture of the muscle occurs. Once an opening in the muscle occurs, abdominal contents such as the liver, stomach, or intestines may herniate through the rupture, enter the chest, and put pressure upon the lungs. The diaphragm muscle is now compromised, as it cannot properly expand and contract. In the authors' experience, most acquired diaphragmatic hernias in cats are the result of being struck by automobiles.
Congenital Diaphragmatic Hernia: Some kittens are born with an incomplete diaphragm muscle. The muscle was not ruptured as in acquired diaphragmatic hernia described previously, but rather was formed incompletely. This results in an abnormal opening or openings within the diaphragm. Congenital diaphragmatic hernias are uncommon and are diagnosed and managed similarly to acquired diaphragmatic hernias.
What are the symptoms?
Signs associated with acquired diaphragmatic hernias may occur immediately after trauma or may not be noted for weeks. Signs of congenital diaphragmatic hernias may appear early in life or at several years of age. Difficulty in breathing is the most common symptom. The degree depends on the extent of the damage and may vary from unnoticeable to extremely labored. In severe cases, the tongue, gums and lips may appear blue. Gastrointestinal upsets such as vomiting or not eating may also be noted when the stomach or intestines herniate through the diaphragm (move through the opening of the diaphragm into the chest). The organs can then become "strangulated" or pinched off by the muscle and other organs.
What are the risks?
The risk depends on the size and location of the hernia within the diaphragm. A small hernia in the diaphragm may go unnoticed and the cat will live a normal life. Cats with severe hernias in the diaphragm, may develop symptoms quickly and die if left unattended.
What is the management?
Anytime a diaphragmatic hernia is suspected, a veterinary exam should be sought at once. Radiographs (X-rays) will often lead to immediate diagnosis. If a diaphragmatic hernia is suspected, surgical correction is the only treatment and should be attempted as soon as the pet is stabilized.