Thoracoscopic anatomic left S¹⁺²ab subsegmentectomy involving the left upper pulmonary vein of the central vein type

A 75-year-old man with suspected lung cancer was admitted to the hospital. A 1.0-cm solid nodule was demonstrated in the left S¹⁺²b subsegment. The left upper pulmonary vein pattern was a central vein type (Figure 1). Based on preoperative 3-dimensional computed tomography (3D-CT) imaging simulation using vascular reconstruction and a lung perspective, we planned a thoracoscopic left S¹⁺²ab subsegmentectomy by dividing the intersegmental parenchyma between S¹⁺² and S³ along the line connecting the root of A³ and the concave portion of the apical pleura (Figure 2). Using 4 access ports, the subsegmental arteries (A¹⁺²ab) were divided, and subsegmental bronchi (B¹⁺²ab) were dissected. Hilar lymph node metastases were not noted on frozen sections. The bronchi were closed with a slip knot after both lungs were inflated, then divided. Due to the inflation–deflation line created with the slip-knot method, S¹⁺²a was slightly brighter than S³c, making the intersegmental line visible. The parenchyma was then divided using a stapler along the inflation–deflation line, as well as the line connecting the root of A³ and the concave portion of the apical pleura. After the parenchymal division, intrasegmental veins (V¹⁺²ab) were identified and divided, and the parenchyma between S¹⁺²b and S¹⁺²c was divided while preserving the intersubsegmental vein (V¹⁺²c) (Video 1). The long surgical time (378 minutes) and blood loss (137 mL) were attributed to the need for extensive adhesiolysis. The tumor was diagnosed as a mucinous adenocarcinoma (T1a N0 M0-1 A1) based on the pathologic evaluation. There were no complications or recurrences at 7-month postoperative follow-up. The patient provided informed consent for study data publication. This study was approved by the institutional ethics committee (approval No. 497; March 30, 2022).

Traditionally, the left upper pulmonary vein is considered to have 3 main variations (apical, apicocentral, and central vein types). Although several branch types have been recently reported, the central vein type is still very rare (2.9% and 2.8%).^, The pulmonary parenchyma is usually easily divided between S¹⁺² and S³ along the intersegmental vein with the anterior approach in the apical or apicocentral vein types because these veins run through the anterior site. In the central vein type, pulmonary veins run posterior to A³. This anatomical difference makes it difficult to divide the demarcation line.

Before and during thoracoscopic segmentectomies, we usually simulate the procedures using 3D-CT images; it was not possible to divide the pulmonary parenchyma along the intersegmental vein with the anterior approach in the central vein type. Referring to the lung perspective of this patient, we noticed an avascular area within the parenchyma at the line connecting the root of A3 with the concave portion of the apical visceral pleura. We reasoned that dividing this area would enable us to perform the intersegmental division in the segmentectomy. Furthermore, the interlobar fissure was incomplete between S¹⁺² and S6. Therefore, we decided that a thoracoscopic left S¹⁺²ab subsegmentectomy was the appropriate procedure. Ultimately, this procedure was completed using the anterior approach by following this simulation.

Segmentectomies require planning based on a precise anatomic understanding. The detailed steps according to each pulmonary vein type in the right upper lobe have been previously reported. The procedural steps might be categorized based on the corresponding patterns in an S¹⁺² segmentectomy. In the apical and apicocentral veins, the parenchymal division between S¹⁺² and S³ along the intersegmental vein (V¹⁺²a) might be preferred in the first step. In contrast, in the central vein type it is recommended that the pulmonary arteries are divided as the first step, and the segmental parenchyma between S¹⁺² and S³ is divided as the second step. In the demarcation line of the intersegment between S¹⁺² and S³, the line connecting the root of A³ and the concave portion of the pleura can be helpful. Although indocyanine green is widely used, this option was not available at our institution. Furthermore, even if indocyanine green had been used, the intersegmental line may not have been visible due to the severe adhesion and thick visceral pleura of this patient. Our proposed procedure-related steps are still experimental because this is the first case performed with this approach. It is therefore necessary to accumulate cases of thoracoscopic S¹⁺² segmentectomy with the central vein type.

A 3D-CT imaging simulation using both vascular reconstruction and a lung perspective is useful when performing a thoracoscopic anatomic S¹⁺²ab subsegmentectomy of the central vein type.