Bilateral pleural thickening: a manifestation of asbestos dust exposure.

Bilateral pleural thickening in a relatively asymptomatic patient without evidence of pulmonary disease is frequently a manifestation of asbestos dust exposure, particularly when it is localized or in the form of a noncalcified pleural plaque. Bilateral pleural thickening will be discovered with increasing frequency if specifically searched for on every radiograph. This radiographic finding is suggested as a more realistic indication of asbestos dust exposure, particularly when correlated with a complete occupational history.     

Trends in pleural radiographic findings in the Navy Asbestos Medical Surveillance Program (1990-1999)

The U.S. Navy Asbestos Medical Surveillance Program is a comprehensive effort to decrease exposure to asbestos, a known health hazard. This study was part of a programmatic review of the Asbestos Medical Surveillance Program database, which included 233,353 radiographic examinations from 1990 to 1999. The initial review focused on incidental findings recorded by B-readers for 23,460 radiographs. Abnormalities reported included bullae (0.68%), cancer (0.56%), cardiac size/ shape abnormalities (1.36%), emphysema (0.74%), subpleural fat (2.62%), fractured ribs (1.24%), hilar adenopathy (0.13%), ill-defined diaphragm (0.46%), ill-defined heart border (0.29%), Kerley lines (0.06%), pleural thickening (2.35%), and tuberculosis (0.27%). The rates by age cohort for pleural abnormalities decreased significantly (30-39 years, chi2 for trend = 23.49, df = 1; 40-49 years, chi2 for trend = 176.21; 50-59 years, chi2 for trend = 401.87), but findings were not significantly different for those > or =60 years of age. This suggests that sequential age cohorts in the program are developing fewer pleural abnormalities; pleural abnormalities have historically been associated with asbestos exposure.     

Diffuse pleural thickening in an asbestos-exposed population: prevalence and causes

Two types of pleural reaction have been described in association with asbestos exposure: pleural plaques and diffuse pleural thickening. This study was undertaken to determine the prevalence and causes of diffuse thickening in asbestos-exposed persons. Serial chest radiographs in 1373 exposed individuals and 717 controls were interpreted according to the ILO scheme by two B readers. Diffuse pleural thickening was defined as a smooth, noninterrupted pleural density extending over at least one-fourth of the chest wall, with or without costophrenic angle obliteration. Among the exposed group, plaques and diffuse thickening occurred with almost equal frequency, 16.5% and 13.5%, respectively. Of the 185 cases with diffuse thickening, the radiographic appearance was most often due to the residual of a benign asbestos effusion (31.3%) or confluent plaques (25.4%). The most commonly held explanation of diffuse thickening, an extension of pulmonary fibrosis to the visceral and parietal pleura, was actually infrequent (10.2%). Among the group with diffuse thickening without asbestosis, the forced vital capacity and single-breath diffusing capacity were significantly lower than those of comparable normal persons and those with confluent plaques.     

Pleural and parenchymal lung diseases from asbestos exposure. CT diagnosis

INTRODUCTION: We report the CT findings of parenchymal and pleural diseases in a group of patients with a history of asbestos exposure, excluding lung cancer (which is not typical in this subjects) and asbestosis (which is a parenchymal fibrosis). MATERIAL AND METHODS: We retrospectively reviewed a series of CT examinations (conventional, helical and high resolution scans) of 21 patients examined from 1995 to 1999. They had pleural plaques (10), round atelectasis (2) and malignant pleural mesothelioma (9). All patients had a history of direct or indirect asbestos exposure, except one with malignant pleural mesothelioma. We evaluated the following CT findings: nodular, plaque or uniform pleural thickening; pleural calcifications; pleural thickening less or greater than 1 cm; pleural margins (regular, polycyclic, spiculated); localization (uni/bilateral hemithorax); distribution (upper, medium or lower region); pulmonary, mediastinal and diaphragmatic involvement; fissural involvement; pleural effusion; lymph node enlargement; lung mass with the comet-tail sign; lung volume (normal, reduced, increased). RESULTS: Pleural plaques were always bilateral and less than 1 cm thick, with calcifications in 80% of the cases. Margins were always regular, polycyclic in 40% of the patients and never irregular. The pulmonary pleura in the mid-chest was involved in cell cases the diaphragmatic pleura in the 50% of the cases and the upper and lower regions in 60% and 80% of the patients, respectively. Round atelectasis (3 cases in 2 patients) was always shown as a parenchymal mass in the lower lobes, posteriorly or posteromedially, with adjacent pleural thickening; its diameter ranged 4.4-6 cm and there was the comet-tail sign. In malignant pleural mesothelioma we always found pleural effusion, with unilateral pleural effusion being the only sign in 2 patients. Other findings were pleural nodules (77.7%), with spiculated (22.2%) and polycyclic (77.7%) margins, more than 1 cm in diameter. The disease was always unilateral. The parenchymal pleural was involved in 77.7% of the cases while the mediastinal and diaphagmatic pleura were involved in 44.4% of the patients. Fissural involvement was demonstrated in 66.6% of the patients. Lymph nodes were enlarged in 66.6% of the cases. The volume of the affected hemithorax was increased (22.2%), decreased (44.4%) or normal (33.3%). DISCUSSION AND CONCLUSIONS: The presence of pleural plaques is a specific sign of asbestos exposure. Round atelectasis may also indicate asbestos exposure, but it can be found in many diseases with pleural inflammation, such as tuberculous effusion, trauma, pulmonary infarct, congestive heart failure, coronary artery bypass. The CT patterns of these two diseases are typical and no other finding is necessary to confirm the diagnosis. CT-guided needle biopsy is needed only if the round atelectasis has an atypical appearance on CT images, that is without the comet-tail sign. Malignant pleural mesothelioma is strongly associated with previous occupational exposure and presents typical CT findings only in an advanced stage (irregular and nodular pleural thickening, pleural effusion, mediastinal and pulmonary contraction for tumor encasement, parenchymal and lymph node metastases), but the differential diagnosis with pleural metastatic disease can be difficult. CT plays an important role in tumor assessment but biopsy is necessary for lesion characterization.     

High-resolution computed tomography of asbestos-related diseases.

There is growing evidence that HRCT can detect both interstitial and pleural disease in advance of conventional clinical or radiographic studies. Limited HRCT scans are roughly competitive in time and cost with 4-view radiographic examinations. The use of limited HRCT for large-scale screening of asbestos-exposed individuals is controversial. Hopefully this will be resolved as we gain greater understanding of the specificity of HRCT and establish guidelines for standardizing technique and interpretation. At present, limited HRCT scans can supplement the chest radiographic evaluation of subjects in whom there is equivocal parenchymal or pleural disease, unexplained abnormalities on pulmonary function tests, or significant coexisting pleural disease that precludes evaluation of the underlying parenchyma. Interstitial abnormalities on HRCT may be reasonably ascribed to asbestos exposure when there is clear historical documentation of significant, remote dust exposure or concomitant evidence of typical bilateral asbestos-related pleural disease. A subpleural distribution of interstitial abnormality in nondependent lung is important to establish the diagnosis of interstitial fibrosis. Although both unilateral pleural and parenchymal fibroses have been reported, lesions should generally be present bilaterally. In individuals with combined asbestos-cigarette smoke exposure in whom symptoms or functional abnormalities are present, HRCT may play a central role in distinguishing emphysematous lung destruction from the peripheral interstitial changes of asbestosis. Finally, in individuals with significant pleural or parenchymal fibrosis, focal lung masses may not be visible on chest radiographs. In these individuals, CT protocols that sample all regions of the thorax are appropriate.     

Asbestos-related pleural disease and asbestosis: a comparison of CT and chest radiography

High-resolution CT (HRCT) has the ability to demonstrate both asbestos-related pleural disease and parenchymal abnormalities consistent with asbestosis. The role of CT in the diagnosis of asbestosis can be defined by comparing it with radiography. We evaluated 60 men who had a history of occupational exposure to asbestos and whose outside chest radiographs were considered abnormal. Chest radiographs (inside films) and HRCT were performed in all patients at our institution and were interpreted independently by experienced radiologists. Outside film results were compiled from the submitted reports. The final conclusion regarding the interpretation of the radiologic examinations was determined by consensus when disagreements existed. Positive predictive values (the likelihood that a positive report is correct) for pleural disease were: outside films 56%, inside films 79%, HRCT 100%. The positive predictive values for parenchymal disease were: outside films 51%, inside films 83%, HRCT 100%. The addition of HRCT to chest radiography is most useful in eliminating false-positive diagnoses of asbestos-related pleural disease caused by subpleural fat and false-positive diagnoses of parenchymal asbestosis in patients with extensive plaques or emphysema obscuring lung detail. The interpretation of chest radiographs in patients exposed to asbestos is often extremely difficult and subjective, and we recommend that positive findings (except calcified plaques) be confirmed with HRCT.     

Comparison of "B" readers' interpretations of chest radiographs for asbestos related changes

RATIONALE AND OBJECTIVES: The purpose of this study was to determine if chest radiographic interpretations by physicians retained by attorneys representing persons alleging respiratory changes from occupational exposure to asbestos would be confirmed by independent consultant readers. MATERIALS AND METHODS: For 551 chest radiographs read as positive for lung changes by initial "B" readers retained by plaintiffs' attorneys, 492 matching interpretative reports were made available to the authors. Six consultants in chest radiology, also B readers, agreed to re-interpret the radiographs independently without knowledge of their provenance. The film source, patient name, and other identifiers on each film were masked. The International Labor Office 1980 Classification of Chest Radiographs(ILO 80) was used with forms designed by the US National Institute of Occupational Safety and Health to record the consult-ants' findings. The results were compared with initial readings for film quality, complete negativity, parenchymal abnormalities,small opacities profusion, and pleural abnormalities using chi-square tests and kappa statistics.Results. Initial readers interpreted study radiographs as positive for parenchymal abnormalities (ILO small opacity profusion category of 1/0 or higher) in 95.9% of 492 cases. Six consultants classified the films as 1/0 or higher in 4.5% of 2,952 readings. Statistical tests of these and other comparable data from the study showed highly significant differences between the interpretations of the initial readers and the findings of the consultants. CONCLUSION: The magnitude of the differences between the interpretations by initial readers and the six consultants is too great to be attributed to interobserver variability. There is no support in the literature on x-ray studies of workers exposed to asbestos and other mineral dusts for the high level of positive findings recorded by the initial readers in this report.     

The ultrasound appearance of asbestos-related pleural plaques.

Twenty-five patients with a history of asbestos exposure and radiological evidence of pleural plaques were examined by ultrasound (US). Non-calcified pleural plaque appeared as a regular area of echo-poor tissue which was well defined adjacent to the diaphragm or lateral chest wall, and varied in thickness from 5 mm to 12 mm. Calcified plaques had echogenic and irregular anterior margins with acoustic shadowing beyond. They were associated with characteristic comet tail and straight line artefact.     

USPIO-enhanced direct MR imaging of thrombus: preclinical evaluation in rabbits

PURPOSE: To identify a system for the quantification of pleural thickening with an acceptable level of interobserver variation and good functional correlation in individuals with pleural disease. MATERIALS AND METHODS: The extent of pleural thickening and plaques was assessed in 50 patients by using the following: (a) a radiographic score based on the International Labour Office system, (b) a subjective simple computed tomographic (CT) score, (c) a subjective comprehensive CT score, (d) an objective nonautomated method, and (e) an objective computer-aided semiautomated method. RESULTS: Similar correlations between the extent of diffuse pleural thickening and forced vital capacity were seen for each system (objective CT, r = -0.72, P <.001; simple CT, r = -0.69, P <.001; radiographic, r = -0.67, P <.001; comprehensive CT, r = -0.66, P <.001). Comparable correlations were observed for total lung capacity. After controlling for extent of diffuse pleural thickening, pleural plaque scores were functionally irrelevant. CONCLUSION: Comparable functional-morphologic correlations were achieved by using different CT and radiographic scoring systems for pleural disease. A subjective simple CT system had the advantages of ease of application and potential to aid in the accurate assessment of the lung parenchyma, which may be important in individuals exposed to asbestos.     

High-resolution computed tomography (HRCT) in the detection of “early asbestosis”

Two radiologists reviewed in masked fashion 144 standard chest radiographs, previously judged as normal by other readers, within a cohort of asymptomatic shipyard workers exposed to amosite. Among the 144 workers we selected subjects (n = 72) who fitted the following criteria: (1) documented occupational exposure to asbestos; (2) absence of any clinical symptomatology suggestive of asbestosis or of any other lung disease. Thirty-eight of them had standard chest radiogrphs that were confirmed as normal by both our radiologists, while 34 showed suspected pleural plaques or a very slight parenchymal involvement. These 72 subjects underwent high-resolution CT (HRCT): pleural plaques were shown in 33, parenchymal alterations in 7, and both pleural and parenchymal involvement in 13. HRCT findings were strictly correlated to the duration of amosite exposure and to the latency time since first exposure. Sensitivity, specificity and diagnostic accuracy values of standard chest radiographs were calculated with respect to HRCT and found to be, for pleural and parenchymal findings respectively: sensitivity 53% and 19%; specificity 72% and 94%; accuracy 60% and 72%. In conclusion, pleural and/or pulmonary involvement in asbestos-exposed workers can be shown by HRCT before the appearance of any symptomatology and abnormality on chest radiography. Furthermore the HRCT findings are correlated to the duration of exposure and latency time. time. Correspondence to; P. Boraschi     

Computed tomography findings in 66 patients with malignant pleural mesothelioma due to environmental exposure to asbestos

We aimed to investigate the computed tomography (CT) findings of malignant pleural mesothelioma (MPM) caused by environmental asbestos exposure. We retrospectively reviewed CT scans of 66 patients, which were performed before any invasive procedure was done. Pleural effusion (80.3%), pleural thickening (77.2%), volume contraction (37.9%), involvement of mediastinal pleura (31.8%) and interlobar fissure (28.8%) were the most common CT findings of MPM. Although none of these findings are pathognomonic for MPM, they may provide valuable clues for the differential diagnosis, at least in patients with a history of asbestos exposure.     

Radiographic findings in pulmonary hypertension from unresolved embolism

Pulmonary artery hypertension with chronic pulmonary embolism is an uncommon entity that is potentially treatable with pulmonary embolectomy. Although the classic radiographic features have been described, several recent investigators report a significant percentage of these patients with normal chest radiographs. In a series of 22 patients, no normal radiographs were seen. Findings included cardiomegaly (86.4%) with right-sided enlargement (68.4%), right descending pulmonary artery enlargement (54.5%), azygos vein enlargement (27.3%), mosaic oligemia (68.2%), chronic volume loss (27.3%), atelectasis and/or effusion (22.7%), and pleural thickening (13.6%). Good correlation with specific areas of diminished vascularity was seen on chest radiographs compared with pulmonary angiograms.     

Radiographic appearance and clinical outcome correlates in 26 patients with severe acute respiratory syndrome

OBJECTIVE: We aimed to evaluate the appearance of chest radiographs in patients with severe acute respiratory syndrome (SARS) and correlate these findings with clinical outcomes. MATERIALS AND METHODS: We retrospectively reviewed the initial radiograph and a series of follow-up chest radiographs in 26 patients who had symptoms and signs consistent with SARS. Twenty-five patients completed the full course of radiographs in the hospital. The initial radiographic features and the distribution of parenchymal, mediastinal, and pleural abnormalities for each patient were evaluated. Follow-up radiographic findings were correlated with clinical outcomes for these patients. RESULTS: Initial chest radiographs showed abnormalities in 23 (88%) of 26 subjects. Eighteen patients (69%) had air-space consolidation, two (8%) had ground-glass attenuation, one (4%) had nodules, and two (8%) had mixed consolidation and nodules. Four patients (15%) had pleural effusion. Younger patients and those with normal initial radiographic findings or unifocal lung lesions had better outcomes. CONCLUSION: The initial predominant radiographic feature of SARS was air-space consolidation in the lateral and lower lung zones. Progressive deterioration to diffuse unilateral or bilateral consolidation in the series of follow-up chest radiographs is associated with a poor prognosis.     

Detection of pleural effusions on supine chest radiographs

A prospective analysis of anteroposterior supine radiographs in 34 patients was undertaken to determine the detectability of pleural effusions on supine radiographs. The presence of pleural effusions and quantity of fluid (small, moderate, or large) were evaluated by using the following radiographic signs: increased homogeneous density superimposed over the lung, loss of the hemidiaphragm silhouette, blunted costophrenic angle, apical capping, elevation of the hemidiaphragm, decreased visibility of lower-lobe vasculature, and accentuation of the minor fissure. Decubitus radiographs were performed to identify and to estimate the quantity of pleural fluid. Sixty-two hemithoraces were evaluated by three observers. From a total of 36 pleural effusions shown on decubitus views, 24 were correctly identified on supine radiographs (sensitivity of 67%, specificity of 70%, and accuracy of 67%). The most frequent but least specific criterion for detecting pleural effusions on supine radiographs is blunting of the costophrenic angle. Other helpful signs include loss of the hemidiaphragm and increased density of the hemithorax. A normal supine radiograph does not exclude a pleural effusion. Our results show that supine radiographs are only moderately sensitive and specific for the evaluation of pleural effusions.     

Asbestos-related pleural disease: value of dedicated magnetic resonance imaging techniques

OBJECTIVES: We sought to compare respiratory-gated high-spatial resolution magnetic resonance imaging (MRI) and radial MRI with ultra-short echo times with computed tomography (CT) in the diagnosis of asbestos-related pleural disease. METHODS: Twenty-one patients with confirmed long-term asbestos exposure were examined with a CT and a 1.5-T MR unit. High-resolution respiratory-gated T2w turbo-spin-echo (TSE), breath-hold T1w TSE, and contrast-enhanced fat-suppressed breath-hold T1w TSE images with an inplane resolution of less than 1 mm were acquired. To visualize pleural plaques with a short T2* time, a pulse sequence with radial k-space-sampling was used (TE = 0.5 milliseconds) before and after administration of Gd-DTPA. CT and MR images were assessed by 4 readers for the number and calcification of plaques, extension of pleural fibrosis, extrapleural fat, detection of mesothelioma and its infiltration into adjacent tissues, and detection of pleural effusion. Observer agreement was studied with the use of kappa statistics. RESULTS: The MRI protocol allowed for differentiation between normal pleura and pleura with plaques. Interobserver agreement was comparable for MRI and CT in detecting pleural plaques (median kappa = 0.72 for MRI and 0.73 for CT) and significantly higher with CT than with MRI for detection of plaque calcification (median kappa 0.86 for CT and 0.72 for MRI; P = 0.03). Median sensitivity of MRI was 88% for detection of plaque calcification compared with CT. For assessment of pleural thickening, pleural effusion, and extrapleural fat, interobserver agreement with MRI was significantly higher than with CT (median kappa 0.71 and 0.23 for pleural thickening, 0.87 and 0.62 for pleural effusion, and 0.7 and 0.56 for extrapleural fat, respectively; P < 0.05). For detection of mesothelioma, median kappa was 0.63 for MRI and 0.58 for CT. CONCLUSION: High-resolution MR sequences and radial MRI achieve a comparable interobserver agreement in detecting pleural plaques and even a higher interobserver agreement in assessing pleural thickening, pleural effusion, and extrapleural fat when compared with CT.     

Malignant pleural mesothelioma: CT manifestations in 50 cases

Malignant pleural mesothelioma, a rare and usually fatal neoplasm that is associated with asbestos exposure, is being encountered with increasing frequency. Pretreatment CT findings from 50 patients with malignant pleural mesothelioma are illustrated. Pleural thickening was found in 46 (92%) of the 50 patients, thickening of the pleural surfaces of the interlobar fissures in 43 (86%), pleural calcifications in 10 (20%), and pleural effusions in 37 (74%). The volume of the involved hemithorax varied appreciably. Contractions of the involved hemithorax was noted in 21 (42%) of 50 patients and contralateral mediastinal shift in seven (14%). Disease beyond the parietal pleura was found in the chest wall (nine patients), mediastinum, lymph nodes, and diaphragm.     

Inhalational anthrax after bioterrorism exposure: spectrum of imaging findings in two surviving patients

The radiographic and computed tomographic (CT) findings in two patients with documented inhalational anthrax resulting from bioterrorism exposure are presented. Chest radiographs demonstrated mediastinal widening, adenopathy, pleural effusions, and air-space disease. Chest CT images revealed enlarged hyperattenuating mediastinal and hilar lymph nodes and edema of mediastinal fat. Chest CT findings are helpful for making the initial diagnosis. To the authors' knowledge, the spectrum and follow-up of CT findings have not been previously described.     

Comparison of plain chest radiography and high-resolution CT in human immunodeficiency virus infected patients with community-acquired pneumonia: a sub-Saharan Africa study

The objective of the study was to determine the proportion of patients with missed lesions on plain chest radiographs compared with high-resolution computed tomography (HRCT) in 49 human immunodeficiency virus (HIV) infected patients with community-acquired pneumonia (CAP). Patients underwent plain chest radiography and HRCT scans of the chest at admission. Microbiological investigations for CAP were performed. An experienced radiologist, without knowledge of clinical or pathological data, reported the chest radiographs and HRCT scans. The study group included 26 females and 23 males, aged 18-53 years (mean age 36 years). Organisms were isolated from 26 patients (53%). In 40 patients (82%), the HRCT scans demonstrated lesions not visualized on the plain chest radiographs. There was 100% correlation between plain radiographic and HRCT scan findings in nine cases (18%). Lesions that were not visualized on the plain radiographs but elucidated on HRCT included: pleural effusion (n = 14), ground-glass opacification (n = 20), pericardial effusion (n = 8), cavitation (n = 4), cysts (n = 4), bullae (n = 4), abscess (n = 1) and pneumothorax (n = 1). In 20 of 23 cases, hilar lymphadenopathy, identified on HRCT, was not recognized on plain chest radiographs. In patients in whom an organism was isolated, a correct HRCT diagnosis of pulmonary tuberculosis, bacterial pneumonia and Pneumocystis carinii pneumonia (PCP) was made in 80%, 84% and 100% of cases, respectively. The proportion of patients with missed lesions on plain chest radiographs in HIV infected patients with CAP was high. This has important implications for management and prognosis. HRCT scans correlate well with the microbiological diagnosis when reported by an experienced radiologist.     

Interleukin-2 therapy for advanced renal cell carcinoma: radiographic evaluation of response and complications

To evaluate the radiographic manifestations of the response of intrathoracic metastases to and the toxicity of interleukin-2 (IL-2) therapy, the chest radiographs and computed tomographic scans of 43 patients receiving 103 cycles of IL-2 treatment and lymphokine-activated killer cells for advanced renal cell carcinoma were reviewed. Among these 43 patients, 31 could be assessed for response of metastatic disease: Complete response was seen in one (3%), partial response in 11 (36%), mixed response in nine (29%), progressive disease in five (16%), and stable disease in five (16%). In 103 treatment cycles radiographic evidence of toxicity included pleural effusions (45.6%), pulmonary edema (21.4%), increased cardiothoracic ratio (16.5%), increased azygos vein diameter (9.7%), pericardial effusion (5.8%), and hilar lymphadenopathy (1.0%). These toxic effects could be distinguished from metastatic disease by a temporal relationship to treatment cycles. A favorable response to IL-2 therapy was significantly correlated (P less than .001) with the presence of pleural effusions.     

Benign collagenous nodule of the pleura associated with pleural plaques

We describe the radiographic, gross morphologic and microscopic appearance of a pleural collagenous nodule presenting as a "solitary nodule." We believe that this lesion is within the spectrum of "pleural plaques," an associated condition present in our patient who had a history of potential asbestos exposure. Awareness of this probably rare variant of a common abnormality may obviate the need for a diagnostic thoracotomy in certain circumstances.