Aberrant Drainage to the Right Upper Pulmonary Vein From the Right Middle or Lower Lung: How Common?

Background: Anatomical variations in pulmonary vein (PV) drainage are critical considerations during right upper or middle lobectomy, as unrecognized aberrant veins can increase surgical risks. Although such variations have been described in anatomical and radiologic studies, surgically verified data under a standardized thoracoscopic approach remain limited. This study investigates the prevalence and patterns of aberrant venous drainage from the right middle lobe (RML) and right lower lobe (RLL) into the right upper pulmonary vein (RUPV). Methods: A total of 213 patients undergoing right upper or middle lobectomy between March 2019 and April 2021 were reviewed from the prospectively collected database. Intraoperative findings documented aberrant venous drainage patterns, including accessory veins and segmental vein variations. We performed video-assisted thoracoscopic surgery (VATS) using a fissure-first, hilum-last to visualize the PV anatomy. Results: Aberrant venous drainage was observed in 60 patients (28%). Variant drainage from the RML to the RUPV was present in 44 patients (20.7%), whereas drainage from the RLL to the RUPV was found in 22 patients (10.3%). The most common pattern involved accessory veins from the RML draining into various branches of the RUPV, noted in 49 patients (61% of cases with aberrant veins). Accessory veins from the RLL were identified in 20 patients (25%). Superior segmental veins of the RLL drained into the RUPV instead of the right inferior pulmonary vein in 3 patients (1.4%). These frequencies are broadly comparable to those reported in previous anatomical and radiologic series. Conclusion: Aberrant venous drainage from the RML and RLL to the RUPV is relatively common and largely consistent with prior anatomical and radiologic descriptions. These findings, based on surgically verified mapping under a standardized VATS approach, confirm and refine existing knowledge and underscore the need for meticulous intraoperative assessment and careful review of preoperative imaging to avoid vascular complications. Future studies should explore multi-institutional data and long-term outcomes to further optimize surgical strategies.