Visceral pleural thickening in asbestos exposure: the occurrence and implications of thickened interlobar fissures

Our plain-English summary of Visceral pleural thickening in asbestos exposure: the occurrence and implications of thickened interlobar fissures, by S.D. Rockoff, E. Kagan, A. Schwartz, et al (Journal of Thoracic Imaging, 1987).

The study

• Authors: S.D. Rockoff, E. Kagan, A. Schwartz, D. Kriebel, W. Hix, P. Rohatgi
• Journal: Journal of Thoracic Imaging
• Published: 1987;2(4):58-66
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000346).

Abstract

We evaluated fissural (ie, visceral pleural) thickening on radiographs in two asbestos-exposed study populations and a control group. Asbestos workers had an incidence of fissural thickening of 54.5% compared with 16.0% in the unexposed control group, with a strong positive statistical effect due to asbestos exposure beyond that attributable to age. Fissural thickening occurred in 85% of workers with parietal plaques and in 36% without pleural plaques. Fissural thickening occurred in 45% without radiographic evidence of pulmonary fibrosis, but it was very common (85%) in those with pulmonary fibrosis. Data analysis showed that fissural thickening responds more strongly to asbestos exposure than does plaque formation, with 21 years of asbestos exposure needed for a 50% chance of developing fissural thickening, while 31 years of exposure were needed for a 50% chance of forming pleural plaques. From a second group of 57 asbestos workers evaluated clinically, 8 were diagnosed as having asbestosis with radiographically clear lungs and fissural thickening. We conclude that visceral pleural thickening is common in asbestos exposure, that it is related to the years since first asbestos exposure, and that its presence may indicate the presence of pulmonary asbestosis, even with radiographically normal lungs.

In plain English

This study looked at chest X-rays for thickening of the interlobar fissures, the thin layers of visceral pleura between the lobes of the lung. The authors compared 220 men occupationally exposed to asbestos with 100 men with no known asbestos exposure. Definite fissural thickening was seen in 120 of the 220 workers (54.5%) and in 16% of the control group. Among the workers, the odds of fissural thickening rose with years since first exposure (odds ratio 1.12 per year, 95% confidence interval 1.08 to 1.15), and the authors reported this was not due to age alone. Pleural plaques were seen in 84 workers (38.2%). Fissural thickening was found in 85% of workers with plaques and 36% of those without. The authors' model predicted a 50% chance of fissural thickening at 21 years and of plaques at 31 years. In a second group, 8 of 59 workers had fissural thickening and signs of asbestosis despite clear or nearly clear lungs on X-ray. The authors concluded that fissural thickening is common in asbestos exposure and may precede X-ray signs of asbestosis.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Radiographic survey of asbestos-exposed workers compared with an unexposed control group, plus a case series of eight workers with fissural thickening and evidence of asbestosis but clear or nearly clear lungs on X-ray
• Who was studied: Control group: 100 adult men with no known asbestos exposure, drawn from 257 consecutive patients evaluated for nonthoracic conditions. Study group A: 220 active or retired occupationally exposed men, drawn from 241 consecutively encountered workers. Study group B: 8 of 59 occupationally exposed workers being evaluated for asbestosis. Location and dates of the groups are not stated.
• Exposure: Occupational asbestos exposure. Fiber types and jobs are not specified. In group A, exposure was measured as the number of years from first exposure until the X-ray; the article also refers to this as years of asbestos exposure. Group B required 10 or more years of occupational exposure.
• Main results:
  • Group A (exposed workers): definite fissural (visceral pleural) thickening was present in 120 of 220 (54.5%).
  • Control group: 16% had definite fissural thickening and 84% had normal fissures.
  • Group A: the odds ratio for fissural thickening per year since first exposure was 1.12 (95% confidence interval 1.08, 1.15). The authors reported that the exposure effect remained strong when age was included in the model.
  • Group A: 84 workers (38.2%) had definite pleural plaques. The odds ratio for plaques per year was 1.09 (1.06, 1.12), and the authors said this could not be fully explained by age.
  • Group A: 85% of workers with pleural plaques also had fissural thickening, and 36% of those with no pleural plaques had fissural thickening.
  • Group A: the models predicted a 50% chance of detectable fissural thickening at 21 years of exposure, compared with 31 years for a 50% chance of detectable pleural plaques.
  • Group A (Table 5): among workers with interstitial pulmonary fibrosis on X-ray, 35 of 41 had fissural thickening. Among those without fibrosis, 85 of 179 had fissural thickening.
  • Group B: 8 of 59 workers had fissural thickening with clear or nearly clear lungs on X-ray and clinical findings indicative or diagnostic of asbestosis. Four had histologic evidence of asbestosis.
• The authors' conclusion: The authors concluded that fissural thickening is common in asbestos exposure and may precede X-ray visualization of pulmonary asbestosis. They added that, in the absence of other causes, fissural thickening may suggest pulmonary asbestosis even when the lungs look clear on X-ray.
• Limitations the authors state:
  • In three of the five group B cases with small airways disease (Cases 3, 5 and 7), the small airways disease could be related at least in part to cigarette smoking.
  • Prior asymptomatic pleural effusions may have contributed to some of the visceral pleural thickening seen in group B patients.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Pleural Thickening, Asbestos Exposure, Pleural Plaques, Pulmonary Fibrosis, Asbestosis.

Related studies

• Thickening of pulmonary interlobar fissures: exposure-response relationship in crocidolite and amosite miners — A. Solomon, L.M. Irwig, et al. (1979)
• CT demonstration of interlobar fissure calcification due to asbestos exposure — S.D. Rockoff (1987)
• Calcified interlobar pleural plaques: visceral pleural involvement due to asbestos — E.N. Sargent, J.S. Felton, et al. (1981)
• Nodular thickening of interlobar fissures: an early manifestation of malignant mesothelioma: a case report — S. Bandoh, J. Fujita, et al. (2001)
• Localized malignant pleural mesothelioma arising in the interlobar fissure: a unique surgical case masquerading clinicopathologically as primary lung adenocarcinoma — X. Guo, J. Watanabe, et al. (2019)
• Calcified plaque in the superior portion of the major fissure. An unusual manifestation of asbestos exposure — S.B. Rupp, H. Jolles (1989)

Browse more research in Journal of Thoracic Imaging, or return to medical research.