By Christie Long
A common veterinary emergency room complaint is difficulty breathing.
Shortness of breathing, an increased abdominal effort associated with breathing, and in the case of cats, open-mouthed breathing — all of these potentially indicate some type of respiratory or cardiac disease.
X-rays of the chest, once the patient is stable enough to undergo the procedure, are the first diagnostic step.
The case of respiratory difficulties is often fluid build-up in the chest cavity. This is known as a pleural effusion and is very different, and has different causes, than fluid that builds up in the lungs themselves.
The chest cavity itself holds the heart, lungs, major blood vessels, esophagus, and other important structures. When fluid or air takes up space in the chest cavity, the lungs are incapable of expanding to their normal volume when the animal breathes in. This causes the animal to breathe rapidly and shallowly. Clearly, the fluid has to be removed so that the animal can breathe more effectively and comfortably.
The procedure for removing the fluid is known as a thoracocentesis, and in it a needle is inserted into the chest cavity and the fluid is suctioned out.
Typically, the respiratory rate slows almost immediately, and the animal relaxes, since the removal of the fluid allows for the lungs to expand more appropriately.
Unfortunately, this is typically not the end of the story. Thoracocentesis is therapeutic, in that it improves the patient’s clinical status, but it is also diagnostic, since the fluid that is retrieved can be analyzed to help determine why it was there in the first place. Usually the fluid will re-accumulate, sometimes rather quickly, unless the inciting cause can be found.
Sometimes the fluid we pull from the chest looks like milk. This is a substance known as chyle. Chyle is composed of fats, water and infection-fighting white blood cells. There is a large vessel in the chest cavity called the thoracic duct.
Pressure on this duct can cause chyle to build up in the chest cavity. Typically this pressure is caused by a cancerous mass or from heart enlargement, secondary to heart disease. The prognosis for either of these cases varies, depending on the type of cancer or the severity of the heart condition.
Another type of chylothorax, as chyle in the chest cavity is called, occurs when we just don’t know the cause. In medicine this is called “idiopathic," and this diagnosis is arrived at once the other possibilities have been ruled out. Idiopathic chylothorax is a challenging condition to treat, as it often requires surgery to ligate or tie-off the thoracic duct.
Often at the same time the pericardium, the sack-like structure that protects the heart, is removed to allow for better drainage of lymphatic fluid. Some cases can be managed quite effectively with a fat-restricted diet and a dietary supplement called rutin, which is thought to enhance the breakdown of fats. Surgery is sometimes needed to effectively stem the flow of chyle and stop the fluid buildup.
Christie Long is a veterinarian at the VCA Animal Hospital in Fort Collins, CO. Long left her job in software sales in 2000 to travel for 13 months. Along the way, she was touched by the plight of the animals she saw and somewhere in the Nepalese Himalayas she vowed to return to school to become a veterinarian. While she often finds end-of-life situations heart-wrenching, she considers herself blessed to be called upon as a trusted adviser to families during difficult times. Dr. Long’s family includes her husband and travel partner, Wiley, their son, Wiley IV, their dogs Pancake and Gizmo and cats Sneaky and Sidh.