VATS right posterior segmentectomy with anomalous bronchi and pulmonary vessels: a case report and literature review

Background Anatomic variation may increase the difficulty and risk of anatomic segmentectomy. The preoperative three-dimensional computed tomography bronchography and angiography (3D-CTBA) can provide a detailed model of the segmental structure, and contribute to precise and safe segmentectomy. Case presentation This is a case of anomalous bronchi and pulmonary vessels in the right upper posterior segment (RS2). Under the guidance of 3D-CTBA, anatomic RS2 segmentectomy was performed accurately and safely. The postoperative condition was uneventful. Conclusions This rare case highlights the importance of 3D-CTBA to guild accurate segmentectomy with anatomic variation.


Background
With the popularization of chest computed tomography (CT), the discovery of small pulmonary nodules is increasingly common, which also promotes the progress of segmentectomy [1,2]. As reported in the previous cases, the anatomic structure of the pulmonary segment is sometimes variable [3][4][5]. The public's attention is now shifting to how to achieve an accurate anatomic segmentectomy. The development and application of various 3D imaging softwares have given a strong technical support in terms of the successful resection [6]. Preoperative reconstruction of the segment can clearly show the anatomic structure and judge whether there are variations, so as to make an accurate surgical plan. In this case, a 34-year-old female patient experienced a ground-glass nodule (GGN) at the right upper posterior segment (RS 2 ). The preoperative three-dimensional CT bronchography and angiography (3D-CTBA) revealed multiple anatomic variations. Owing to the detailed planning of the operation, video-assisted thoracoscopic surgery (VATS) RS 2 segmentectomy was performed successfully.

Case presentation
A 34-year-old female was admitted to us with a GGN in RS 2 , which was discovered by chest CT during a health checkup 1 year ago. A review of CT indicated that the subpleural GGN was slightly larger than before, with a diameter of 7 mm and a CT value of -400HU (Fig. 1). She had no positive signs, no history of smoking, no history of malignant tumors, and no family history of lung cancer. Preoperative 3D-CTBA revealed multiple variations in the right upper lobe: (1) The apical subsegmental bronchi(B 1 a and B 1 b) originated from the posterior segmental bronchus (B 2 ) and the anterior segmental  (Fig. 2). VATS anatomic RS 2 segmentectomy and lymph node sampling were conducted accurately With the guidance of 3D-CTBA (Fig. 3); all anatomic variations were successfully detected during the operation (Fig. 4). Minimally invasive adenocarcinoma (MIA) was the fast-frozen pathology. The chest radiograph illustrated that the right lung was completely redilated, and on the second postoperative day, the incisal margin of

Video description
Intravenous general anesthesia combined with doublelumen endotracheal intubation and contralateral one-lung ventilation were performed. The observation port was made in the seventh intercostal space of the posterior axillary line, and the operation port in the fourth intercostal space of the anterior axillary line. The surgical procedure was as follows: (1) Thoracoscopic exploration revealed a subpleural nodule at the RS 2 . (2) The parietal pleura was sectioned by harmonic, and then the Nos.11 lymph nodes were removed. (3) The V 2 t was dissociated and pulled by silk, and the Nos.12 and 13 lymph nodes around the bronchus were completely removed. (4) After ligating the V 2 t, the B 2 was dissected out and transected with a thick tissular (blue cartridge) 45-mm long endostapler (EC45A, JJMC, USA). (5) According to the preoperative 3D-CTBA, the other 2 veins were judged as the intersegmental veins; hence, they were all preserved. (6) We reventilated the right lung with pure oxygen because the posterior segmental artery was very difficult to ligate; when the intersegmental plane was clear after 18 min, the segmental hilum was released sufficiently to expose the posterior segmental artery, and then the artery was ligated safely. (7) The intersegmental plane was divided along the inflation-deflation line using the endostaplers; thus, the posterior segment was removed successfully. A sterile glove was used to collect the specimen. Bleeding and air leakage were not observed after the pleural injection of inflation. No. 24 chest drainage tube was placed in the observation port. The incision was sutured after the right lung was completely dilated. The operative time was 75 min, and intraoperative blood loss was 50 mL.

Discussion and conclusions
In recent years, anatomic segmentectomy for early lung cancer is one of the biggest hotspots in thoracic surgery. It can not only completely resect the tumor but also preserve the normal lung tissue to the maximum extent [7]. The distribution of bronchus, artery, and vein in the pulmonary segment exists variations in some patients. The key to the implementation of this operation is to accurately grasp the anatomic structure of the target segment. The 3D-CTBA can provide a precise anatomic structure, identify the intrasegmental and intersegmental veins from different views [8]. Therefore, some complicated pulmonary segmentectomy should be performed under the guidance of 3D-CTBA [9,10].
The efficacy of 3D reconstruction for thoracic surgery has been previously described [11], Kimihiro et al. [12] first reported the application of 3D-CTBA in VATS segmentectomy. At present, the main softwares for 3D reconstruction of segment include IQQA, DeepInsight, etc. [13,14]. All the reconstructive softwares can offer precise anatomic structure of pulmonary segments, but sometimes, it is difficult for surgeons to skillfully use them. In our institution, with the assistance of the radiologists, we adopt the CT pulmonary angiography based technology to reconstruct the anatomic structure of each patient who undergo segmentectomy. It shows the precise structure of bronchi, arteries and veins in a natural surgical field view.
In all kinds of segmental resection, RS 2 segmentectomy is a common procedure, but anatomic variations may increase its difficulty and risk [15]. Xinfeng et al. [16] reported a tracheal bronchus and a variable central vein entering the left atrium dorsal to the right pulmonary artery trunk in a patient who underwent VATS RS 2 segmentectomy. Tadashi et al. [17] reported anatomic variations in bronchi and pulmonary vessels in a patient who underwent thoracoscopic RS 2 segmentectomy. However, to the best of our knowledge, bronchial variation associated with variant pulmonary vessels has rarely been reported. The normal anatomic structure of RS 2 consists of B 2 , Asc.A 2 , the recurrent artery (Rec.A 2 ), intrasegmental veins (V 2 t and V 2 b) and intersegmental veins (V 2 a and V 2 c), but in this case, the 3D-CTBA revealed multiple variations: (1) The bronchopulmonary trees of the right upper lobe were divided into (B 2 + B 1 a) and (B 3 + B 1 b); the (B 2 + B 1 a) variation might have been mistaken for B 2 without the guidance of 3D-CTBA. (2) There was only 1 intrasegmental vein (V 2 t) without another intrasegmental vein (V 2 b); intersegmental veins might have been transected as intrasegmental veins without the preoperative 3D-CTBA. (3) The posterior segmental arteries originated from the superior trunk without Asc.A 2 . They were very difficult to expose; therefore, we released the hilum of segment first to expose the arteries sufficiently, and then the artery was safely ligated. This novel strategy has rarely been reported.
In conclusion, we present a successful strategy for VATS RS 2 segmentectomy with multiple anatomic variations.