Pneumonia (Interstitial) in Cats

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Interstitial Pneumonia in Cats

Pneumonia refers to an inflammation in the cat's lungs. Interstitial pneumonia, meanwhile, refers to a form of pneumonia in which the inflammation occurs in the walls of the cat's alveoli (the air cells of the lungs), or in the interstitium (the spaces between the tissue cells of the alveoli). The alveoli are cellular components of the cat's airway -- where oxygen and carbon dioxide are exchanged.

Interstitial pneumonia can occur in both cats and dogs, with some breeds being more susceptible than others. If you would like to learn more about how this disease affects dogs, please visit this page in the PetMD health library.

Symptoms and Types

Symptoms vary depending on the severity of the disease. Some symptoms that may appear in the cat include tachypnea, coughing, dyspnea, mild fever, and discharge from the eyes. Exposure to toxic elements, for example, may also result in gastrointestinal signs, such as vomiting, diarrhea, and a decreased amount of urine production.


There is a wide range of conditions that can lead to interstitial pneumonia in cats. Bronchiolitis obliterans organizing pneumonia, a congenital (birth) defect, is characterized by inflamed airways and surrounding tissues, and increased odds of interstitial pneumonia.

Other causes include lung cancer, and metabolic disorders such as uremia, in which excess levels of urea and other nitrogenous waste products, which normally are excreted through the urine, appear in the cat's blood.

Infectious diseases such as feline immunodeficiency virus (FIV), and exposure to toxic elements through inhalation of dust, gas, or vapor, are also suspect in the diagnosis of causative factors.


There are a wide variety of diagnostic procedures that can be used if symptoms related to interstitial pneumonia appear, including a urine analysis, blood tests, X-ray imaging of the pleural cavity (the area between the chest wall and lungs), and an electrocardiography (ECG) test, used for measuring the electrical impulses of the heart, and for the detection of irregular heart rhythms related to increased pressure on the lungs.

Two more diagnostic procedures that are common when pneumonia is suspected are a tracheal wash, which involves a collection of the fluids and substances lining the trachea, and a bronchoscopy, by which a small tube with a tiny camera attached is inserted into the mouth and led into the bronchial airway so that a visual inspection can be made.

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