食道癌における右上葉区域肺静脈分岐走行異常の術前診断の意義

Preoperative evaluation of right superior pulmonary vein anomaly for safe thoracoscopic esophagectomy

◆要旨：右上葉区域肺静脈が右上肺静脈から独立して気管支背側を通過し，左房や肺静脈に流入する分岐走行異常は比較的稀である．食道癌に対して胸腔鏡下食道亜全摘術を行った2症例において，術前CTで右主気管支または中間気管支幹背側を走行する右上葉区域肺静脈の破格を診断した．右主気管支背側を走行する症例では本静脈の気管支末梢側・中枢側を分けてリンパ節郭清を行い，中間気管支幹背側の末梢を走行する症例では本静脈は郭清範囲の辺縁に存在し手術操作に影響はなかった．食道外科領域において右上葉区域肺静脈の分岐走行異常は気管支背側を走行する部位により手術への影響が異なり，術前画像診断および手術操作に注意を要すると考えられる．

　An anatomical variation of the right superior pulmonary vein passing behind the right main bronchus or bronchus intermedius is rare. This anomalous vein drains directly into the left atrium or pulmonary veins, and has been discussed mainly by thoracic surgeons and cardiologists previously. We report two surgical cases of esophageal cancer with the rare anomalous pulmonary veins which were identified preoperatively. In one case, the anomalous vein passed behind the right main bronchus and we performed subcarinal lymph node dissection dividing the area into a central and a peripheral part of the vein. In the other case, the anomalous vein ran behind the bronchus intermedius located peripherally in the mediastinum and was less interfering during lymph node dissection. We preserved those anomalous veins in both cases. The influence of the anomalous veins to subcarinal lymph node dissection for esophageal cancer differs depending on the route of the vein in the mediastinum. Careful evaluation of preoperative computed tomographic images is essential to identify those variant veins for a safe subcarinal lymph node dissection for esophageal cancer.