Respiratory change in size of honeycombing: Inspiratory and expiratory spiral volumetric CT analysis of 97 cases

Purpose: The purpose of this study was twofold: to evaluate the change in s ize of honeycomb cysts with respiration using inspiratory-expiratory spiral volumetric CT (I-E SVCT) and to establish the pathologic basis of this cha nge. Method: Ninety-seven patients, who had honeycombing associated with end-sta ge pulmonary fibrosis on end-inspiratory 1 to 2 mm collimation high resolut ion CT (HRCT), underwent I-E SVCT (3 mm collimation, pitch 1, breath-hold t ime 20 s, reconstruction interval 1 mm, FOV 16-20 cm, high frequency algori thm). I-E SVCT scans were assessed on images obtained in the transverse pla ne and volumetric sagittal, coronal, and oblique reformations. The histolog ic findings were assessed in four inflated and fixed lungs that showed hone ycombing at postmortem HRCT. Results: In 63 patients (65%), a small percentage of the cysts did not chan ge in size at end-expiration, while in the remaining patients, all the cyst s decreased in size. Assessment of volumetric multiplanar reformations show ed that cysts that decreased in size during exhalation communicated with ai rways and represented bronchiolectasis rather than true cysts, while the ot her cysts did not communicate with the airways. Similar findings were found in pathologic specimens. Conclusion: The majority of, but not all, honeycomb cysts seen on HRCT repr esent dilated bronchioles that communicate with the proximal airways and ch ange in size with respiration.