Section: Veterinary Care In-depth
Diagnosis In-depth
Diagnostic tests are needed to recognize PF. 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.
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