Technical report: Cystic air spaces in the lung: change in size on expiratory high-resolution CT in 23 patients.
OBJECTIVE
To determine the presence of change in size of air-filled cysts in the lung on expiration by comparison between inspiratory and expiratory high-resolution computed tomography (CT) scans.


METHODS
Inspiratory and expiratory high-resolution (1-mm collimation) CT scans were obtained in 23 patients with lung cysts due to a variety of lung diseases. The 23 patients had a total of 27 types of cystic lesions including bullae (n=7), honeycomb cysts due to fibrosing alveolitis (n=11), lymphangioleiomyomatosis (LAM, n=2), cystic adenomatoid malformation (n=1), and bronchiectasis (n=6). An adequate expiratory effort, with at least 5% decrease in the anteroposterior or transverse thoracic diameter, was required for inclusion in the study. Inspiratory and expiratory scans at corresponding anatomic levels were compared to determine any change in size of the cysts on expiration.


RESULTS
Cystic lesions due to bronchiectasis, LAM and fibrosing alveolitis decreased in size on expiratory CT. In six of seven cases bullae decreased in size, and in one patient with a single bulla it remained unchanged. In one case a single cyst due to cystic adenomatoid malformation increased in size on expiration.


CONCLUSIONS
The majority of lung cysts decrease in size on expiration suggesting that they communicate with the airways.
Department of Radiology, University of British Columbia and Vancouver Hospital and Health Sciences Centre, Canada.
S A
SA
Worthy
M J
MJ
Brown
N L
NL
Müller
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001987:Bronchiectasis / Q000000981:diagnostic imaging; D015615:Cystic Adenomatoid Malformation of Lung, Congenital / Q000000981:diagnostic imaging; D003560:Cysts / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging; D018192:Lymphangioleiomyomatosis / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging; D011658:Pulmonary Fibrosis / Q000000981:diagnostic imaging; D012119:Respiration; D014057:Tomography, X-Ray Computed