Asbestos Health Effects : Clinical Evaluation, Part 2

by CDC

(Page 7 of 9)

Fibrosis found symmetrically in the lower aspects of both lungs is typically caused by asbestos. Fibrotic lung disease due to asbestos inhalation is often associated with pleural plaque formation, which eliminates other etiologic possibilities such as drugs; radiation; sarcoidosis; collagen vascular disorders; Goodpasture syndrome; hemosiderosis; idiopathic pulmonary fibrosis secondary to lung infections; and inhaled silica, coal dust, or organic dusts. Smoking effects should be considered in the evaluation of early asbestosis, lung function tests, and respiratory symptoms. Health-care practitioners should be alert for a differential diagnosis of treatable fibrotic diseases, where intervention may be of benefit.

Lung Cancer

Asbestos-associated lung cancers produce the same symptoms as cancers due to other etiologies.

Lung cancer caused by asbestos exposure cannot be differentiated from cancer caused by other environmental factors. The histologic type of lung cancer and its anatomic location are of no significant value in deciding whether or not an individual lung cancer is attributable to asbestos. Clinical signs and symptoms of asbestos-related cancer do not differ from those of lung cancer of other causes (International Expert Meeting on Asbestos, Asbestosis, and Cancer 1997). The differential diagnosis of lung cancer in a patient exposed to asbestos should include other possible etiologies, such as exposure to cigarette smoke, arsenic, chloromethyl ethers, chromium, nickel, and ionizing radiation. Clubbing of the distal phalanges or cyanosis of the nail beds can occur.

Mesothelioma

The latency period for mesothelioma is 20 years or more, but the onset of symptoms is sudden.

Both pleural and peritoneal mesotheliomas can be seen in a patient exposed to asbestos, although peritoneal mesotheliomas are very rare. These tumors are rapidly invasive locally. Although onset of mesothelioma is not sudden, symptoms of the disease can be. Mesothelioma frequently presents with pleural effusion, dyspnea, and chest pain. Less common presenting symptoms are cough, weight loss, and fever. Peritoneal mesotheliomas are more difficult to diagnose by noninvasive means than pleural occurrences are. They are frequently detectable by abdominal palpation as an expanding "doughy" feeling. Early diagnosis is essential to maximize potential for successful intervention. If caught early and treated, there is a greater chance of survival. Pleural effusion can precede the mesothelioma; if pleural effusion is detected, the patient should be evaluated aggressively. Mesothelioma is seldom associated with etiologies other than asbestos exposure.

Laboratory Tests and Special Procedures

Chest radiograph and pulmonary function tests are important procedures in diagnosing asbestos-associated disease.

Established tests and procedures helpful in diagnosing asbestos-associated disease include radiographic techniques, pulmonary function tests, and possibly computerized tomography scanning. Neither sputum studies nor blood chemistry studies are useful in diagnosing asbestos-associated disease in the clinical setting.

Quantification of the amount and type of asbestos fibers and asbestos bodies in lung tissue or bronchoalveolar lavage fluid or both might be useful in individual patients, where indicated, to determine the level of past exposure to asbestos, and aid in evaluation of differential diagnosis.

Histopathologic confirmation is required for suspected asbestos-related malignancies.

Radiographic Techniques

Radiographic results should not be used preferentially in diagnosing asbestosis.

The chest radiograph is the basic tool for assessing asbestos-associated parenchymal and pleural disease. Radiographic findings may include interstitial fibrosis in the lower lung fields and thickening of both the parietal and visceral lung pleura. Parietal pleural thickening generally appears as a lobulated prominence of the pleura adjacent to the thoracic margin. Visceral pleural thickening is generally more diffuse and appears as interlobar fissure thickening on lateral films. Further, according to Kamp and Weitzman (1997), the chest radiograph in cases of asbestosis usually reveals small parenchymal opacities with a nodular or reticular pattern or both. The interstitial process characteristically begins in the lower lung zones and is associated with bilateral midzone parietal pleural plaques. In the early stages, combined interstitial and pleural involvement can cause a hazy, ground-glasslike appearance that blurs the heart border ("shaggy heart" sign) and the diaphragm on the chest radiograph. The pleural thickening might entrap the lung parenchyma and form a benign pleural-based mass (rounded atelectasis) that mimics bronchogenic carcinoma. Honeycombing and upper lobe involvement generally do not develop until advanced stages of asbestosis. Hilar and mediastinal lymphadenopathy are not typically present. Pulmonary effusion can be present. A system has been developed by ILO for radiographic rating of the changes in pneumoconiosis. Persons certified to use this rating system are referred to as "B readers."

The diagnosis of asbestosis should be made in the context of the overall clinical presentation and should include, but not emphasize, radiographic findings. The association of pleural thickening and calcification enhances diagnostic accuracy. Although open lung biopsy is a definitive diagnostic test for asbestosis, it is rarely used in the clinical setting.

About the Author

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