Fibrotic Hardening of the Lungs in Cats

Pulmonary Fibrosis in Cats

Cats can suffer from many forms of pneumonia, pulmonary fibrosis being one of them. The development of this disease results in inflammation and scarring of the tiny air sacs of the cat's lungs and lung tissue. The reactive scarring of the lungs results in fibrotic tissue buildup, where the tissue becomes excessively thick, reducing the ability of the affected sacs to pass oxygen into the blood stream. Therefore, as the disease progresses, less oxygen is passed into the body’s tissues when the cat breathes.

The factors which initiate pulmonary fibrosis are still unknown; however, hereditary factors and a variety of micro-injuries to the air sacs are suspected. Recent evidence also suggests abnormal wound healing in the lung as a mechanism for fibrosis. It may exist concurrently with cancer in cats. Affected cats are usually middle-aged or elderly.

The condition or disease described in this medical article can affect both dogs and cats. 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

The signs and symptoms displayed by the cat generally progress slowly; these include:

  • Anorexia
  • Cyanosis
  • Lethargy
  • Cough (nonproductive)
  • Shortness of breath
  • Increased respiratory rate and effort
  • Open-mouth breathing/panting
  • Exercise intolerance


The underlying cause for pulmonary fibrosis is usually unknown (idiopathic). However, it may be also due to:

  • Genetics
  • Viral infection(s)
  • Acute pancreatitis
  • Toxins or drugs
  • Oxygen toxicosis (a pathological condition caused by oxygen)
  • Environmental damage (e.g., exposure to polluted air or cigarette smoke)


The biggest problem in diagnosing and treating pulmonary fibrosis is that the disease may be far along before symptoms begin to appear.

Your veterinarian will conduct a full physical examination, including a chemical blood profile, complete blood count, and chest X-rays. Other diagnostic tools include an echocardiography to determine whether the heart is enlarged, a computed tomography (CT) scan to view the cat's lungs three dimensionally, and biopsy samples of the affected tissues for microscopic examination.

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