CT assessment of the normal upper-lobe lung volume in idiopathic pleuroparenchymal fibroelastosis

Abstract

Idiopathic pleuroparenchymal fibroelastosis (iPPFE) is characterized by upper lobe-dominant fibrosis involving the pleura and subpleural lung parenchyma. Upper-lobe lung volume (UL-volume) loss is a hallmark of iPPFE. The UL volume included dense consolidation, bronchiectasis and pleural thickening, in addition to the normal parenchyma. Therefore, we hypothesized that assessing the normal parenchymal UL volume would accurately indicate disease severity and mortality risk in patients with iPPFE. This retrospective study included two cohorts of 144 patients with iPPFE. Each lobe volume was quantitatively measured using three-dimensional computed tomography, and the normal UL volume was assessed from − 950 Hounsfield units (HU) to − 750 HU. Patients with a lower normal UL volume had significantly shorter median survival than those with higher volume (6.63 years vs. 2.88 years, p < 0.001). Furthermore, the normal lung volume decreased longitudinally, with decreases occurring predominantly in the upper lobes. In multivariate analysis, a lower normal UL volume was significantly associated with increased mortality after adjusting for age, sex and FVC. A composite scoring model including age, sex and the normal UL volume more accurately predicted the risk of death. These results suggested measuring normal UL volume provides useful information for iPPFE management by predicting mortality risk.