Postoperative changes in low attenuation volume according to the number of resected subsegments: a retrospective cohort study

Background: The demand for segmentectomy is increasing owing to its favorable long-term outcomes. Preservation of the lung parenchyma through segmentectomy may contribute to long-term survival; however, the morphological changes occurring in the residual lung parenchyma after segmentectomy are not fully understood. Low attenuation volume (LAV) is known as an indicator of emphysematous changes and has been used for morphological analysis of the lungs. This study aimed to investigate the postoperative changes in the residual lung after both lobectomy and segmentectomy and to evaluate the LAV in relation to the number of resected subsegments. Methods: We included 56 patients who had undergone lobectomy or segmentectomy for non-small cell lung cancer or other lung diseases between April 2020 and November 2021, and high-resolution computed tomography preoperatively and postoperatively within 6 months. Three-dimensional reconstruction images were created to calculate the LAV and the percentage of low attenuation volume-to-lung volume (LAV%). The variables of the ipsilateral residual lung lobes, excluding the affected lobe, were evaluated for all patients pre- and postoperatively. The relationship between radiological parameters and the number of resected subsegments was examined. A comparative analysis was conducted by dividing the patients into two groups, with a threshold of the change in LAV% (ΔLAV%) ≥0.7% used to indicate hyperinflation using a receiver operating characteristic curve analysis: SS ≤5 group, those with ≤5 resected subsegments (n=32); and SS ≥6 group, those with ≥6 resected subsegments (n=24). Results: 0.56%, P=0.10, respectively). The correlation analysis showed a weak but significant correlation between ΔLAV% and the number of resected subsegments (R=0.30, P=0.02). Significant increases in the change in LAV (median: SS ≤5, -0.68 mL; SS ≥6, 2.17 mL; P=0.04) and ΔLAV% (median: SS ≤5, -0.26%; SS ≥6, 0.0065%; P=0.01) were observed in the SS ≥6 group, but no significant increase in the change in lung volume in the ipsilateral residual lung lobes was observed compared with that in the SS ≤5 group (median: SS ≤5, 130 mL; SS ≥6, 335 mL, P=0.08). The postoperative pulmonary function was not significantly different between the two groups. Conclusions: The number of resected subsegments correlated positively with ΔLAV%. An increase in ΔLAV% was frequently observed in patients in the SS ≥6 group. This suggests that hyperinflation can be induced after extensive lung resection, whereas it was rarely observed after limited resection, which could preserve normal lung parenchyma.