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. 2015 Dec;70(12):1156-62.
doi: 10.1136/thoraxjnl-2015-207653. Epub 2015 Oct 29.

Pulmonary cysts identified on chest CT: are they part of aging change or of clinical significance?

Tetsuro Araki  1 , Mizuki Nishino  1 , Wei Gao  2 , Josée Dupuis  3 , Rachel K Putman  4 , George R Washko  4 , Gary M Hunninghake  4 , George T O'Connor  5 , Hiroto Hatabu  1
Affiliations

Pulmonary cysts identified on chest CT: are they part of aging change or of clinical significance?

Tetsuro Araki et al. Thorax. 2015 Dec.

Abstract

Objective: To investigate the prevalence and natural course of pulmonary cysts in a population-based cohort and to describe the CT image characteristics in association with participant demographics and pulmonary functions.

Materials and methods: Chest CT scans of 2633 participants (mean age 59.2 years; 50% female) of the Framingham Heart Study (FHS) were visually evaluated for the presence of pulmonary cysts and their image characteristics. These findings were correlated with participant demographics and results of pulmonary function tests as well as the presence of emphysema independently detected on CT. The interval change was investigated by comparison with previous CT scans (median interval 6.1 years).

Results: Pulmonary cysts were seen in 7.6% (95% CI 6.6% to 8.7%; 200/2633). They were not observed in participants younger than 40 years old, and the prevalence increased with age. Multiple cysts (at least five) were seen in 0.9% of all participants. Participants with pulmonary cysts showed significantly lower body mass index (BMI) (p<0.001). Pulmonary cysts were most likely to appear solitary in the peripheral area of the lower lobes and remain unchanged or slightly increase in size over time. Pulmonary cysts showed no significant influence on pulmonary functions (p=0.07-0.6) except for diffusing capacity of the lung for carbon monoxide (DLCO) (p=0.03) and no association with cigarette smoking (p=0.1-0.9) or emphysema (p=0.7).

Conclusions: Pulmonary cysts identified on chest CT may be a part of the aging changes of the lungs, occurring in asymptomatic individuals older than 40 years, and are associated with decreased BMI and DLCO. Multiple pulmonary cysts may need to be evaluated for the possibility of cystic lung diseases.

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Figures

Figure 1
Figure 1
A transaxial CT image of a 60-year-old female who is a former smoker with 4.2 pack-years shows a solitary cyst in the right lower lobe of the lungs. The cyst is circumscribed with a thin wall and measures 17 mm in diameter.
Figure 2
Figure 2
CT images of a 47-year-old female show a solitary round cyst (arrow) with a thin wall in the middle lobe of the right lung (a). She is a former smoker with 18 pack-years. (b) Low attenuation color-mapping overlaid images (threshold of -950 HU, indicated in light blue areas) at transaxial (b) and sagittal reconstruction (c) demonstrate the distinct solitary pulmonary cyst (arrows) with the background lung parenchyma with a diffuse infiltration of mild centrilobular emphysema.
Figure 3
Figure 3
Prevalence of pulmonary cysts in association with age. Plotted dots indicate the prevalence in each age group. Vertical lines extending from each plot represent 95% CI (confidence interval) with horizontal lines at the top and bottom representing upper and lower limits, respectively.
Figure 4
Figure 4
Longitudinal observations of pulmonary cysts. (a) Participants (N=109) who had pulmonary cysts detected on both CT scans (MDCT1 and MDCT2, median interval of 6.1 years) are plotted for diameter of pulmonary cysts and participant's age. Each short line represents an interval change of a pulmonary cyst in diameter in each participant. Red lines (N=39) indicate increased in diameter, green lines (N=68) unchanged, and blue lines decreased (N=2). Increase or decrease in diameter was defined as changes in diameter of more than 2 mm accounting for measurement variability. (b) A curved-fit line represents an overall tendency, slight increase of the diameter of pulmonary cysts with age. Shaded area represents 95% CI (confidence interval).
Figure 4
Figure 4
Longitudinal observations of pulmonary cysts. (a) Participants (N=109) who had pulmonary cysts detected on both CT scans (MDCT1 and MDCT2, median interval of 6.1 years) are plotted for diameter of pulmonary cysts and participant's age. Each short line represents an interval change of a pulmonary cyst in diameter in each participant. Red lines (N=39) indicate increased in diameter, green lines (N=68) unchanged, and blue lines decreased (N=2). Increase or decrease in diameter was defined as changes in diameter of more than 2 mm accounting for measurement variability. (b) A curved-fit line represents an overall tendency, slight increase of the diameter of pulmonary cysts with age. Shaded area represents 95% CI (confidence interval).
Figure 5
Figure 5
Transaxial CT images at the lower level (a) of a 51-year-old female who has no smoking history show multiple thin-walled pulmonary cysts. These cysts are located predominantly in lower lobes, mostly in subpleural or peripheral areas. Comparison to the previous scan (b) (obtained 7.1-year previously) demonstrates an increase of the cysts in size and number. Cysts in the right lower lobe (a, b, arrows) increased in size (medial: 5 to 10 mm, lateral: 9 to 11 mm). The cyst in the middle lobe (a, arrowhead) was not detected on the previous image.
Figure 5
Figure 5
Transaxial CT images at the lower level (a) of a 51-year-old female who has no smoking history show multiple thin-walled pulmonary cysts. These cysts are located predominantly in lower lobes, mostly in subpleural or peripheral areas. Comparison to the previous scan (b) (obtained 7.1-year previously) demonstrates an increase of the cysts in size and number. Cysts in the right lower lobe (a, b, arrows) increased in size (medial: 5 to 10 mm, lateral: 9 to 11 mm). The cyst in the middle lobe (a, arrowhead) was not detected on the previous image.
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