Asbestosis Symptoms Take Decades to Develop
A history of asbestos exposure may provide the first clue to the diagnosis of asbestos diseases such as asbestosis and asbestos pleural disease. It often takes decades between the patient’s asbestos exposure and the appearance of early symptoms such as shortness of breath and chest pain.
A physician may test for asbestosis by using a stethoscope to listen for basal crackles or persistent high–pitched sounds that are characteristic of the disease. An x–ray may show small irregular opaque areas, usually in the lower lobes of the lungs. Pleural plaques indicative of asbestos pleural lung disease may also show up in an x–ray. However, x–rays are limited in detecting early asbestos disease, sometime yielding false positives for smokers as well as false negatives.
Asbestosis is Often Detected Through CT Scans
A computed tomography or CT scan may be more useful in indicating asbestosis and asbestos–related pleural disease than the chest x–ray, particularly in those cases in which the chest x–ray is ambiguous or in asbestos–exposed patients who have normal chest x–rays. A CT scan is a radiographic technique that uses a computer to combine multiple x–ray images into a two dimensional cross–sectional x–ray image. A machine rotates 180 degrees around the patient's body, sending out a thin x–ray beam at numerous points. Crystals at the opposite points of the beam pick up and record the absorption rates of the varying thickness’ of tissue and bone. The computer turns the information into a detailed picture.
A high resolution CT scan (HRCT or “thin–slice” scan) can be even more accurate than a conventional CT scan. HRCT differs from the conventional CT in that it uses a very narrow x–ray beam (1–1.3mm slice thickness compared to conventional 8–10mm) and a high spatial frequency reconstruction to provide extremely high definition images of the lungs (High Resolution CT of the Lung, Radiology Update).
When only asbestos–related pleural disease is found using an x–ray or CT scan for diagnosis, it is not uncommon to later find pathologic evidence of asbestosis that was undetectable except on biopsy or autopsy. Some researchers feel that it is this sub–radiographic asbestosis which explains symptoms and pulmonary function abnormalities in individuals with evidence of only asbestos–related pleural disease, while others feel it is the impact of the pleural scarring on breathing mechanics which accounts for these findings.
Labels: DIAGNOSIS
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