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Pulmonary Fibrosis in Dogs

Pulmonary fibrosis is one form of pneumonia that can affect dogs. The development of this disease results in inflammation and scarring of the tiny air sacs of the 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 than normal is passed into the body’s tissues when the dog 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 bronchitis in dogs. Affected dogs are usually midde-aged or elderly.

Symptoms and Types

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

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

Causes

West Highland White terriers and other terriers, such as the Staffordshire, Cairn, Border, and Norfolk, are genetically predisposed to pulmonary fibrosis. However, the underlying cause for this type of pneumonia is usually idiopathic. Other causes include:

• 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)

Diagnosis

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 dog's lungs three dimensionally, and biopsy samples of the affected tissues for microscopic examination.