Compensatory expansion of the right middle lobe: volumetric and functional analysis of the changes after right upper or lower lobectomy

The right middle lobe often poorly expands after right upper lobectomy. Postoperative pulmonary function may be inferior after right upper lobectomy than after right lower lobectomy due to poor expansion of the middle lobe. This study examined the difference in the postoperative right middle lobe expansion and pulmonary function between right upper and right lower lobectomy. Patients who underwent right upper or right lower lobectomy through video-assisted thoracic surgery (n = 82) were enrolled in this retrospective study. Pulmonary function tests and computed tomography were performed preoperatively and at 1 year postoperatively. Using three-dimensional computed tomography volumetry, the preoperative and postoperative lung volumes were measured, and the predicted postoperative forced expiratory volume in 1 s was calculated. Middle lobe volume ratio (i.e., ratio of the postoperative to the preoperative middle lobe volume) and the postoperative forced expiratory volume in 1 s ratio (i.e., ratio of the measured to the predicted postoperative forced expiratory volume in 1 s) were compared between right upper and right lower lobectomy. Compared with the patients who underwent right upper lobectomy (n = 50), those who underwent right lower lobectomy (n = 32) had significantly higher middle lobe volume ratio (1.15 ± 0.32 vs. 1.63 ± 0.52, p < 0.001) and postoperative forced expiratory volume in 1 s ratio (1.12 ± 0.12 vs. 1.19 ± 0.13, p = 0.010). The right middle lobe showed more expansion and better recovery of postoperative pulmonary function after right lower lobectomy than after right upper lobectomy.