Pulmonary edema, commonly called fluid in the lungs, is often caused by pneumonia, but has several other causes. In this condition, the tiny air sacs (alveoli) within the lungs become filled with fluid, making it difficult for the lungs to carry out their function of inhaling oxygen and exhaling carbon dioxide.
Common symptoms of pulmonary edema include coughing, difficulty breathing, wheezing or noisy breathing, weakness, and bluish tongue or lips. Depending on the underlying cause, the condition can come on rapidly or develop slowly as part of another chronic illness. While fluid in the lungs can be a mild, manageable health issue, severe cases are life-threatening, and any dog showing difficulty in breathing needs immediate veterinary care.
What Is Pulmonary Edema?
Pulmonary edema is not a disease or condition that occurs on its own, but rather, is an indication of an underlying problem that causes fluid to leak from blood vessels around and inside the lungs. This fluid then accumulates in the tiny air sacs within the lungs that carry out gas exchange. The fluid reduces the amount of space within the alveoli, so the animal cannot draw in as much air, and impairs the ability of the alveoli to carry out gas exchange, so the affected dog's lungs are unable to effectively exchange carbon dioxide for fresh oxygen.
Pulmonary edema is typically divided into two categories based on the underlying cause: cardiogenic pulmonary edema, which is caused by a problem with the heart and noncardiogenic pulmonary edema, which has a cause other than heart trouble.
Symptoms of Pulmonary Edema in Dogs
Depending on the underlying cause of the pulmonary edema, symptoms can vary and might come on suddenly or build slowly over time. The following are the most common symptoms to watch for.
When pulmonary edema develops slowly, the symptoms can be subtle at first. You might merely observe that your dog seems less active than usual and is breathing harder than would be expected. Or your dog might have a persistent cough. However, in more severe cases, your dog will noticeably work at breathing. It will pant and you might see the dog's sides moving in and out with each breath.
Dogs with long-standing pulmonary edema often lose weight due to lack of appetite and overall poor health. Your dog will have little energy to engage in normal activities, such as playing or going for walks.
Severe pulmonary edema greatly reduces the lung's ability to bring oxygen into the dog's body. If blood oxygen levels fall to dangerous levels, you might notice that your dog's tongue and gums are a bluish color. This is called cyanosis and requires an emergency call to your veterinarian.
Causes of Pulmonary Edema
There are two basic categories of pulmonary edema: cardiogenic and noncardiogenic.
Cardiogenic Pulmonary Edema
Cardiogenic means coming from the heart. In this type of pulmonary edema, the dog has an underlying heart condition that has caused left-sided heart failure. The heart failure increases the pressure within the capillaries (tiny blood vessels) within the dog's lungs, causing the capillaries to leak fluid which slowly accumulates in the lung's air sacs.
Common heart conditions that lead to pulmonary edema in dogs include dilated cardiomyopathy, which is an enlarged heart, hypertrophic cardiomyopathy, which means that the walls of the heart are thicker than normal, and defects of the mitral valve inside the heart. Usually, pulmonary edema caused by heart disease comes on slowly.
Noncardiogenic Pulmonary Edema
Noncardiogenic pulmonary edema, not surprisingly, means edema caused by underlying conditions other than heart-related. In these types of pulmonary edema, it isn't high pressure within the capillaries that causes fluid to leak, it's an alteration in the normal permeability of the blood vessels that allows the fluid to leak out and fill up the alveoli.
There are quite a few noncardiogenic causes of pulmonary edema, although pneumonia is the most common. Other causes include cancer, not enough protein in the blood, anemia, near-drowning, electrocution, snake venom, smoke inhalation, airway obstruction, and heartworms. Generally, this type of pulmonary edema comes on suddenly.
Diagnosing Pulmonary Edema in Dogs
X-rays are the prime tool for diagnosing pulmonary edema, as they will reveal the fluid inside the dog's lungs. X-rays can also reveal an enlarged heart or other abnormalities in the heart muscle.
Your veterinarian will also listen to your dog's lungs and heart with a stethoscope. Often, there are distinctive crackling lung sounds with pulmonary edema. With cardiogenic pulmonary edema, the heart sounds are often also abnormal.
Generally, your vet will run blood tests to assess your dog's overall health and may run specific blood tests to rule out or diagnose various underlying health conditions that may have caused the pulmonary edema. A full physical examination will be carried out, as well.
Treatment & Prevention
The treatment for pulmonary edema depends somewhat on the underlying cause, but generally, any dog in respiratory distress will immediately be put on supplementary oxygen through a mask.
If the cause of edema is determined to be cardiogenic, diuretics, which are drugs that help reduce excess liquids in the body, will be prescribed. Furosemide is the most common diuretic used for this purpose in dogs. Vasodilators, such as nitroglycerine, are also commonly prescribed. These drugs help open blood vessels, thus reducing the work required for the heart to pump blood. Your dog might need to remain on these medications long-term, possibly for the rest of its life. Along with medications, rest and a low-sodium diet are usually recommended.
If the edema is noncardiogenic, treatment can vary quite a bit, depending on the cause. Diuretics are often prescribed, as well as anti-inflammatory drugs. An airway obstruction might require immediate surgery or endoscopy, while pneumonia requires antibiotics. If the edema is caused by an accident, such as near-drowning, electrocution, or smoke inhalation, treatment largely consists of allowing the dog to rest while receiving supplement oxygen.
Depending on the cause of the edema and your dog's condition, the animal might need to remain in the veterinary hospital for monitoring and extended treatment, or you might take your pet home the same day, along with any prescribed medications.
Because pulmonary edema has many causes, most of which are difficult to predict or prevent, the condition is not easily preventable other than by keeping your pet in good health and visiting the veterinarian regularly for checkups that might detect health problems before they become serious.
Prognosis for Dogs With Pulmonary Edema
It's difficult to generalize on the prognosis for dogs with pulmonary edema because there are so many causes. Typically, however, the prognosis is fairly good for dogs in early stages of heart disease but not so good if the dog has progressed to congestive heart failure. When it comes to noncardiogenic pulmonary edema, the prognosis depends on the severity of the underlying cause. Dogs who survive accidents, such as near-drowning, generally will recover fully, as will dogs with pneumonia.
Causes, Symptoms & Treatments for Fluid in the Lungs in Dogs. Carolina Veterinary Specialists.
Pulmonary Edema. DVM360.