Ann Thorac Surg 1998;66:1799-1800
© 1998 The Society of Thoracic Surgeons
Case Reports
Anatomy of inferior pulmonary vein should be clarified in lower lobectomy
Satoru Sugimoto, MDa,
Osamu Izumiyama, MDa,
Akio Yamashita, MDa,
Masahito Baba, MDa,
Tadashi Hasegawa, MDa
a Department of Thoracic and Cardiovascular Surgery, Hakodate Municipal Hospital, Hakodate, Japan
Accepted for publication May 13, 1998.
Address reprint requests to Dr Sugimoto, Department of Thoracic and Cardiovascular Surgery, Hakodate Municipal Hospital, Yayoicho 2–33, Hakodate, 040 Japan
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Abstract
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We successfully performed surgery for carcinoma of the lung on 2 patients with the anatomic variation of the middle lobe vein draining to the right inferior pulmonary vein. This variation is surgically important because division of the right inferior pulmonary vein may result in blockage of middle lobe vein drainage in right lower lobectomy. Surgeons must always pay attention to this variation when performing the right lower lobectomy.
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Introduction
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Surgeons usually ligate and divide the right inferior pulmonary vein (PV) without meticulous attention to its tributaries [1] when performing right lower lobectomy because the former generally consists of the right lower lobe vein only. However, 2 patients undergoing surgical treatment for carcinoma of the lung in our hospital in December 1997 had the anatomic variation of a middle lobe vein emptying into the right inferior PV. One of these was a patient undergoing right lower lobectomy, and had we ligated and divided the right inferior PV trunk without preservation of the middle lobe vein, the patient might have suffered from severe edema of the middle lobe resulting from blockage of venous return. We present the 2 cases with this PV variation and discuss the necessity of definitive exposure of the tributaries of the right inferior PV when performing right lower lobectomy.
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Case reports
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Patient 1
Computed tomography (CT) on a 37-year-old woman revealed a circular mass, and carcinoma of the middle lobe was diagnosed. The clinical stage of cT1N0M0 indicated a surgical resection. A middle lobectomy and mediastinal lymph node dissection by R2a was performed via right standard thoracotomy. First, the right superior PV was exposed, and the middle lobe vein was sought but not found. Next, the interlobular pulmonary artery was exposed and the two middle lobe arteries were ligated and divided. After this procedure, the middle lobe vein draining to the right inferior PV was exposed. The former was ligated and divided, and the remaining procedure for the middle lobectomy and R2a mediastinal lymph node dissection were successfully performed. The postoperative course was uneventful. Pathologic diagnosis was well-differentiated adenocarcinoma, stage pT1N0M0. The operation proved to be curative. The variation of the middle lobe vein drainage was evident in a retrospective review of the preoperative CT (Fig 1).
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Fig 1. Preoperative computed tomography of the chest in patient 1. The middle lobe vein (single arrow) runs toward the mediastinum and empties into the right inferior pulmonary vein (double arrow) in one stem.
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Patient 2
A 61-year-old man was diagnosed with small-cell carcinoma of the right lower lobe by CT and sputum cytology. The clinical stage was cT2N0M0. Surgical resection was indicated after remission by two cycles of combined chemotherapy with carboplatin and etoposide. An operation including a right lower lobectomy and mediastinal lymph node dissection by R2a was performed. In the operation, since the right inferior PV trunk was too short to ligate and divide in this case, its tributaries were exposed. The careful ligation and division of the right lower lobe veins disclosed drainage of the middle lobe vein to the right inferior PV, which was preserved. The remaining procedure, right lower lobectomy and mediastinal lymph node dissection by R2a, were successfully performed. The postoperative course was uneventful. Pathologic diagnosis was small-cell carcinoma and squamous cell carcinoma of the lung, stage pT2N0M0. The operation was curative. The variation of middle lobe vein drainage was evident in a retrospective review of the preoperative CT (Fig 2).
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Fig 2. Preoperative computed tomography of the chest in patient 2. The middle lobe vein (single arrow) runs toward the mediastinum and empties into the right inferior pulmonary vein (double arrow) (left panel) in one stem. The vessel posterior to the middle lobe vein (right) is the middle lobe artery.
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Comment
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Surgeons may divide the right inferior PV trunk without exposure of its tributaries when performing right lower lobectomy when the right inferior PV trunk is long enough to divide safely. However, this procedure causes blockage of venous return from the middle lobe vein in patients who have the anatomic variation of middle lobe vein drainage to the right inferior PV as was seen in our cases. The ligation of a PV that should be preserved can lead to severe lung edema, which may cause infection or respiratory distress, postoperative complications that could be life-threatening.
This variation in the bronchovascular trees is well described by Dr Yamashita [2]. In his study, 4.8% of 120 specimens had the middle lobe vein emptying into the right inferior PV. This frequency of this variation must be taken into account. If surgeons ligate and divide the right inferior PV trunk without identifying the drainage of the middle lobe veins when performing a right lower lobectomy, the postoperative complications described in this article caused from the middle lobe edema can occur. This surgically significant variation also exists in the left lung, in which the lingular segment vein can empty into the left inferior PV at a frequency of 2.5% [2]. Thus, surgeons also must look for this variation when performing left lower lobectomies.
The retrospective review of the preoperative CT film obviously showed the middle lobe vein emptying into the right inferior PV (Figs 1, 2), which clearly suggests that preoperative diagnosis of this variation is quite possible. We conclude that physicians should diagnose drainage of the middle lobe vein or the lingular segment vein in each case, and surgeons must expose the tributaries of the right or left inferior PVs and identify their origins when performing right or left lower lobectomies. Moreover, these variations should be more heavily stressed in textbooks on lung surgery.
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References
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- Sabiston D.C., Jr Neoplasm of the lung. In: Sabiston D.C., Jr, Spencer F.C., eds. Gibbon’s surgery of the chest. Philadelphia: WB Saunders Co, 1983:453-538.
- Yamashita H. Variations in the pulmonary segments and the bronchovascular trees. In: Yamashita H., ed. Roentgenologic anatomy of the lung. Tokyo: Igaku-shoin, 1978:70-107.
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