Pulmonary Fibrosis (PF) in Dogs

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In-depth Information on Diagnosis

Diagnostic tests are needed to recognize PF in dogs. A tentative diagnosis can often be made based on the results of the history, physical examination and chest X-rays. In diagnosing PF, it is important to exclude other diseases and your veterinarian may refer you to a specialist if the diagnosis is in doubt. Details about the different diagnostic tests include:

  • Complete medical history and physical examination
  • Radiography (chest X-rays) to detect a mild diffuse increase in interstitial lung densities, which is generally evident throughout the lungs in dogs with PF. Bronchial markings may be prominent, especially if there is also bronchitis.
  • A complete blood count (CBC) to determine general health and check for secondary conditions. The CBC in dogs with PF is usually normal.
  • Biochemistry and serum blood tests to determine general health and check for secondary conditions.
  • A heartworm test
  • Testing arterial blood gases to determine oxygen levels. This is a sensitive test for verifying the presence of significant lung disease. Many veterinary hospitals do not have the equipment to run this test but blood can be analyzed easily at a local human hospital.
  • A pulse oximetry test to measures oxygen content of arterial blood. This test provides information similar to an arterial blood gas but is not as sensitive as the blood gas. However, if the pulse oximetry shows abnormal oxygen content, this is sufficient.
  • A tracheal wash, also called a transtracheal wash, in which a fluid sample from the trachea (windpipe) is obtained and analyzed. This test is done under local anesthetic by inserting a needle and catheter across the trachea and advancing the catheter into the windpipe. This test is most advantageous in coughing dogs.
  • Bronchoalveolar lavage (BAL) is a test in which fluid samples from the bronchus and alveolar (lung) tissues are obtained. There are a number of techniques used, and anesthesia is required. This test results are abnormal in active alveolitis/fibrosis (lung inflammation leading to scar tissue). The sample results are characterized by increased neutrophils but without evidence of an infection.
  • Bronchoscopy, which is a procedure consisting of placing a small flexible fiberoptic tube into the airway. It can be used to visualize the airways and perform a BAL test, and will usually establish the diagnosis and rule out other potential lung diseases, such as inflammatory lung disease, lungworms, fungal infections and cancer. This is often a referral procedure.
  • A fine-needle lung aspirate, which is a procedure that consists of placing a small needle into the lungs and obtaining a small tissue sample. It is one method of identifying diffuse lung disease caused by cancer or certain infections.
  • Lung biopsy, the surgical removal of a piece of lung tissue, can lead to a definitive diagnosis of lung fibrosis. However, it is an invasive test and is rarely done. 
  • In-depth Information on Treatment 

    Treatments for PF in dogs may include one or more of the following:

  • Treatment of PF must be individualized based on the severity of the condition, the cause, secondary diseases or conditions and other factors that must be analyzed by your veterinarian. Therapy of idiopathic pulmonary fibrosis is frustrating because as the underlying cause of lung inflammation is rarely determined or controlled and therapy does not reverse pre-existent fibrosis.
  • A trial course of bronchodilators using sustained-release theophylline, aminophylline or oxtriphylline should be considered.
  • Bronchodilator drugs may increase the vigor of contraction of the respiratory muscles, which may be useful in dogs with chronic shortness of breath.
  • Antibiotics are not helpful.
  • Prednisone can be used if tests (BAL) determine active airway inflammation with an absence of infection. This will not reverse the existing fibrosis but may decrease ongoing lung inflammation (alveolitis) and prevent further damage. Chronic treatment is controversial but one approach is to prescribe pulsed prednisone (for example, twice-daily dosing for one week per month).
  • The benefits, if any, of the immunosuppressive drug, cyclophosphamide, have not been evaluated in the dog but this is commonly used in humans with PF and active alveolitis.
  • The prognosis in advanced pulmonary fibrosis is unfavorable and gradual clinical deterioration is expected. Severe hypoxemia (low oxygen content in blood) or progressive right-sided heart dysfunction may be observed in very advanced cases.
  • Many dogs are eventually euthanized.
  • Follow-up Care for Dogs with Pulmonary Fibrosis

    Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical and may include the following:

  • Administer prescribed medications as directed by your veterinarian. Be certain to contact your veterinarian if you are experiencing problems treating your dog.
  • Serial blood gas determinations and bronchoalveolar lavage cytology may be done to monitor therapy and the clinical course of the disease, though this is infrequently done because of the need for general anesthesia.
  • Eliminate smoke, chemicals, dusts or fumes from your pet’s environment.
  • Notify your veterinarian if your dog is coughing. This is a prominent clinical sign and bronchitis is likely to be present. This is a different diagnosis than PF.
  • Control your dog’s obesity. Discuss a weight loss plan if your dog is obese.
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