Robot-assisted thoracoscopic right upper lobectomy with displaced B3 and absence of minor fissure: a case report

B3 downward-shifting is a rare bronchial anomaly characterized by abnormal pulmonary arteries associated with downward displacement of B3 and complete fusion between the right upper and middle lobes. We report a case of robot-assisted thoracoscopic right upper lobectomy in a patient with lung cancer with B3 downward-shifting. An 81-year-old male was diagnosed with non-small cell lung cancer in S3 of the right upper lung. Preoperative three-dimensional computed tomography angiography revealed a B3 bronchus derived from the middle lobe bronchus and an anterior segmental pulmonary artery variation. Robot-assisted thoracoscopic surgery right upper lobectomy with ND2a-1 was performed via four-port incisions and an assist incision. No interlobar fissure was observed between the right upper and middle lobes. After dissecting B1+2, the displaced B3 root was dissected. The displaced A3a was difficult to dissect because of an extremely severe complete fissure. Therefore, we dissected the bronchus preceding from the cranial side. To confirm a minor fissure, indocyanine green was administered intravenously, and the interlobar boundary was identified as the line separating the dark and green lung parenchyma. The boundary was divided using mechanical staples. No surgical complications occurred. Using three-dimensional reconstruction imaging and systemic indocyanine green administration, we successfully performed a right upper lobectomy through robot-assisted thoracic surgery.


Introduction
B 3 downward-shifting is a rare bronchial anomaly with an incidence of 0.6%. This malformation was first reported in 1951. It is characterized by abnormal pulmonary arteries associated with a downward displacement of B 3 and complete fusion between the right upper and middle lobes [1,8]. An incomplete interlobar fissure makes video-assisted thoracoscopic surgery (VATS) lobectomy difficult and is an excellent predictor of morbidity after a VATS lobectomy [3]. Therefore, the preoperative identification of patients' exact anatomical features is crucial to prevent intraoperative and postoperative complications. Herein, we report a case of robot-assisted thoracoscopic right upper lobectomy in a patient with lung cancer with B 3 downward-shifting and abnormal arteries and an extremely severe complete fissure between the right upper and middle lobes.

Case presentation
An 81-year-old male presented with abnormal opacity in the upper lobe of the right lung on chest computed tomography (CT), which was performed during a follow-up visit for prostate cancer. Chest CT revealed a 23-mm solid nodule in S3 of the right upper lung ( Supplementary Fig. 1 Supplementary Fig. 2). Bronchoscopic biopsy revealed non-small cell lung cancer. Three-dimensional computed tomography (3D-CT) angiography revealed that A 3 a independently branched from the main pulmonary artery and was accompanied by a displaced B 3 a, whereas A 3 b had a common trunk with the medial artery (A 4 + A 5 ) and was accompanied by a displaced B 3 b (Fig. 1). The right superior pulmonary vein showed normal branching (Fig. 1). We diagnosed non-small cell lung cancer as c-T1cN0M0 stage IA3. Robot-assisted thoracoscopic surgery (RATS) right upper lobectomy with ND2a-1 was performed via four-port incisions and an assist incision. Two 12-mm robotic ports were placed in the eighth intercostal space on the anterior axillary line and the posterior axillary line, and an 8-mm robotic port was placed in the seventh intercostal space and eighth intercostal space. An assist incision was made in the fourth intercostal space on the anterior axillary line, including an assistant port as a carbon dioxide (CO 2 ) insufflation port. The da Vinci Xi surgical system (Intuitive Surgery, Sunnyvale, CA, USA) was docked on the right side of the patient. Robotic instruments included a 30° camera, long bipolar grasper, and Cadier forceps in the left arm and monopolar scissors or a vessel sealer extended in the right arm. A CO 2 insufflation system (AirSeal system, ConMed, Utica, NY, USA) was used at a set pressure of 8 mmHg. No interlobar fissure was observed between the right upper and middle lobes; however, an interlobar fissure was observed between the right upper and lower lobes. First, the mediastinal pleura was dissected to reveal the hilum of the right upper lobe (RUL). Then, the apical and posterior subsegmental arteries (A 1 b + A 2 a), apical subsegmental artery (A 1 a), V 1 + 2 + 3 , and A 3 b were exposed and dissected sequentially (Fig. 2a,  b). We then dissected the right upper bronchus (B 1+2 ) after dissecting the #11 s lymph node. Further, the posterior Fig. 1 Three-dimensional computed tomography images. a The displaced B 3 shares a common trunk with the right middle bronchus. b A 3 a independently branched from the main pulmonary artery. A 3 b shares a common trunk with A 4 + A 5 . c A 3 a is accompanied by the displaced B 3 a, and A 3 b is accompanied by the displaced B 3 b. d The right superior pulmonary vein has normal branching subsegmental artery (A 2 b) was exposed and dissected using a mechanical stapler. After tunneling the interlobar plane between the upper and lower lobes, it was dissected using a mechanical stapler. The displaced B 3 b was dissected, the displaced B 3 a was encircled, and the displaced B 3 root was redissected (Fig. 2c). The A 3 a was then exposed and dissected using a mechanical stapler (Fig. 2d). The displaced A 3 a was difficult to dissect because of an extremely severe complete fissure. Therefore, we dissected the bronchus preceding from the cranial side. To confirm a minor fissure, indocyanine green (ICG) (7.5 mg) was administered intravenously via the peripheral venous catheter. After administration, the surgical field was visualized using the integrated fluorescence imaging function of a Firefly Fluorescence Imaging camera (Intuitive Surgical). The interlobar boundary was identified as the line separating the dark and green lung parenchyma (Fig. 2e). The boundary was marked on the visceral pleura using monopolar scissors and divided using mechanical staples (Fig. 2f). The resected lobe was extracted following mediastinal node dissection. The total operation time was 6 h and 32 min, and the console time was 5 h and 32 min. Minimal blood loss was observed. No surgical complications occurred. The postoperative course was uneventful. The patient was discharged 8 days after the surgery. The pathological stage was p-T1cN0M0 stage IA3.

Discussion
To the best of our knowledge, this is the first surgical report on RATS lobectomy confirming an extremely severe complete fissure after intravenous ICG administration in a patient with lung cancer and B 3 downward-shifting. This case report has two crucial clinical implications. First, we identified Fig. 2 Intraoperative findings. a The right superior pulmonary vein is exposed, and V 1 + 2 + 3 is identified. b The view after dissecting V 1 + 2 + 3 . A 3 b shares a common trunk with A 4 + A 5 . c The view after dissecting displaced B 3 b bronchus. The displaced B 3 shares a common trunk with the right middle bronchus. d The view after dissecting displaced B 3 bronchus. A 3 a independently branches from the main pulmonary artery. e Intraoperative identification of interlobar boundaries by intravenous indocyanine green administration. f The red dotted line represents the interlobar boundaries between the right upper and middle lobes. RML right middle lobe, RUL right upper lobe (colour figure online) 1 3 not only a displaced B 3 arising from the RML bronchus but also abnormal pulmonary arteries, accompanied by a severe incomplete interlobar fissure. Second, we demonstrated that intravenous ICG administration was effective in identifying interlobar fissures. B 3 downward-shifting results in abnormal pulmonary arteries, where A 3 arises from the interlobar artery and shifts downwards alongside B 3 into the middle lobe, accompanying the displaced B 3 downwards [1,8]. Furthermore, because of the presence of an extremely severe complete fissure instead of an incomplete horizontal fissure, the right side becomes a mirror image of the left side, which makes the surgery more complicated [8]. When selecting the resection procedure, it is crucial to take into account the principles of oncology, as the upper and middle lobes may originate from the same embryonic lung lobe. In this case, the lesion was predominantly located in S3, closer to S2. Thus, we determined that the right upper lobectomy would provide an adequate margin from the tumor and guarantee a cure. However, a bilobectomy could have been a viable option as well.
Recently, the efficacy of RATS in patients with an incomplete interlobar fissure has been reported [6]. Preoperative or intraoperative 3D-CT or bronchoscopy helps recognize an accurate anatomy [2]. In this case, 3D-CT angiography helped to recognize and imagine the definitive position of the displaced B 3 and the distribution and running style of the pulmonary arteries supplying the right upper lobe. A 3 a showed independent branching from the main pulmonary artery and was accompanied by the displaced B 3 a, whereas A 3 b had a common trunk with A 4 + A 5 and was accompanied by the displaced B 3 b (Fig. 1). As expected preoperatively, the dissection of B 1 and B 2 revealed the anatomical location of B 3 and A 3 , thereby making the dissection of the displaced B 3 and A 3 safer and easier to perform (Fig. 1). Thus, recognizing anatomical anomalies based on 3D-CT imaging helps us develop an optimal strategy, resulting in safe and successful surgery. In addition to the anatomical complexity, the endoscopic component of the procedure, which required careful surgical manipulation, may have contributed to the longer duration of the operation; thus, there is room for improvement.
To identify severe incomplete interlobar fissures between the right upper and middle lobes, intravenous administration of ICG was required. This involved eliminating the original blood flow by dissecting the dominant pulmonary artery and separating the target lobe from other areas exhibiting normal blood flow.
Previous studies have reported near-infrared fluorescence mapping using ICG as a helpful tool in identifying the intersegmental plane in minimally invasive segmentectomy [4,7]. This technique helps to identify the interlobar fissure in RATS lobectomy in patients with severe incomplete interlobar fissures [6]. Moreover, intravenous ICG administration does not require inflation to detect the segmental plane and creates more surgical working space, thereby facilitating thoracoscopic surgery. In this case, a severely incomplete fissure with a displaced B 3 was properly dissected with intravenous ICG administration. Nakanishi et al. have reported a similar case of a displaced B 3 in which the interlobar plane was recognized by intravenous ICG and right upper lobectomy was performed [5].

Conclusions
We successfully performed a right upper lobectomy for lung cancer in a patient with a displaced B 3 bronchus by RATS. Preoperative 3D-CT imaging and systemic ICG administration led to surgical success.