Costal pleura: appearances at high-resolution CT

Our plain-English summary of Costal pleura: appearances at high-resolution CT, by J.G. Im, W.R. Webb, A. Rosen, et al (Radiology, 1989).

The study

• Authors: J.G. Im, W.R. Webb, A. Rosen, G. Gamsu
• Journal: Radiology
• Published: 1989;171(1):125-31
• Cited by: 79 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The appearance of the costal pleura at high-resolution computed tomography (CT) was evaluated with a cadaver and 25 normal subjects. This was contrasted with the high-resolution CT appearance of the costal pleura in 15 patients with mild pleural thickening, 13 of whom had been exposed to asbestos. On high-resolution CT scans in the normal subjects, a 1-2-mm-thick line of soft-tissue attenuation at the point of contact between lung and chest wall represents the visceral and parietal pleura, pleural contents, endothoracic fascia, and innermost intercostal muscle. In a paravertebral location, the innermost intercostal muscle is lacking, and a thin line seen on high-resolution CT scans reflects pleura and endothoracic fascia. Transverse thoracic and subcostal muscles and extrapleural fat pads can be seen as tissue internal to a rib and may be confused with pleural thickening. In 13 of the 15 patients with mild pleural thickening, the 1-3-mm-thick pleura was separable from the underlying normal intercostal muscle by a layer of extrapleural fat. High-resolution CT was more sensitive than CT with 1-cm collimation in depicting this degree of pleural abnormality.

In plain English

This study looked at how the costal pleura (the lining between the lungs and the ribs) appears on high-resolution CT scans. The authors compared scans of a formalin-fixed male cadaver thorax with its cut and microscopic sections. They also retrospectively reviewed scans of 25 people without pleural disease and 15 patients with mild pleural thickening, 13 of whom had a history of asbestos exposure. No fiber types were named. In all 25 normal subjects, a 1-2-mm line was visible where lung met chest wall. Intercostal veins, small chest-wall muscles and fat pads could mimic pleural thickening. All 15 patients showed a 1-3-mm line of thickened pleura. In 13, a layer of fat separated it from the rib, muscle or vein beneath in most locations. In 11 patients thickening also showed on conventional 1-cm CT, but in all 13 scanned both ways some areas seen on high-resolution CT were missed. Patients with extensive plaques were excluded. The authors concluded that high-resolution CT was more sensitive than 1-cm CT for this degree of pleural abnormality.

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: Anatomic correlation in one cadaver plus a retrospective review of CT scans from normal subjects and patients with mild pleural thickening
• Who was studied: One formalin-fixed male cadaver thorax. 25 patients without pleural disease used as normal subjects (21 men, aged 45 to 85, mean 64). 15 patients with pleural thickening, all with focal pleural calcifications on CT (13 men, aged 45 to 75, mean 62). An additional 8 very overweight normal subjects. The study was done at the University of California San Francisco; study dates are not given.
• Exposure: 13 of the 15 patients with pleural thickening had a history of asbestos exposure. No fiber type, job or dose is given.
• Main results:
  • In the cadaver, a 1-2-mm line of soft-tissue density was visible in each space between the ribs. It represented the parietal pleura, endothoracic fascia and innermost intercostal muscle combined.
  • In all 25 normal subjects, a 1-2-mm line was visible on high-resolution CT where lung met chest wall.
  • In all 25 normal subjects, segments of intercostal veins that looked like focal pleural thickening were seen at one or more levels.
  • In normal subjects, a line probably representing subcostal muscle was seen inside the ribs in 4 of 25 scanned at heart level. Fat inside the more lateral ribs was seen in 12 of 15 scanned with extended window settings.
  • In the 8 severely overweight normal subjects, the pleura was no more visible than in average-weight normal subjects.
  • All 15 patients with pleural thickening showed a 1-3-mm line of thickened pleura on high-resolution CT. In 13, a fat layer separated it from the rib, muscle or vein in most locations. This fat measured up to 4 mm thick, usually about 1-2 mm.
  • In 11 patients, pleural thickening was visible on conventional 1-cm CT scans. In all 13 patients who had both kinds of scan, some areas of thickening seen on high-resolution CT were not visible on conventional CT.
  • Six patients, all with asbestos exposure, had focal pulmonary fibrosis on high-resolution CT. In all patients, most areas of pleural thickening were next to normal-appearing lung.
• The authors' conclusion: The authors concluded that high-resolution CT was more sensitive than CT with 1-cm collimation in showing this mild degree of pleural abnormality. They also wrote that they hesitate to diagnose thickening beside the spine unless it looks uniformly thickened on multiple sections and is separated from the underlying vein by a fat plane.
• Limitations the authors state:
  • In the patients with thickening, thickening of the visceral pleura could not be told apart from thickening of the parietal pleura.
  • Patients with extensive plaques were excluded.
  • Extended window settings were not used with conventional CT, which made fat difficult to see.
  • It was unclear whether focal thickening of the line beside the spine in normal subjects reflected a partly visible intercostal vein.

Topics

Medical terms in this study, explained in our Lexicon: Pleura, High-Resolution CT (HRCT), Pleural Thickening, Parietal Pleura, Endothoracic Fascia.

Related studies

• Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests — S. Neri, A. Antonelli, et al. (1994)
• Pleural plaques in asbestos-exposed workers: reproducibility of a new high-resolution CT visual semiquantitative measurement method — G.S. Meirelles, J.I. Kavakama, et al. (2006)
• High-resolution computed tomography abnormalities in ex-insulators annually exposed to asbestos dust — J.M. Soulat, D. Lauque, et al. (1999)
• High resolution computed tomography and lung function in asbestos-exposed workers with normal chest radiographs — C.A. Staples, G. Gamsu, et al. (1989)
• High-resolution computed tomography of asbestos-related diseases — D.R. Aberle (1991)
• Asbestos-related focal lung masses: manifestations on conventional and high-resolution CT scans — D.A. Lynch, G. Gamsu, et al. (1988)

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