Gaetano Rocco
INDICATIONS/CONTRAINDICATIONS
Right lower lobe segmentectomies account for up to 23% of all segmentectomies. Time-honored indications for these segmentectomies include benign lung lesions, localized and active postprimary tuberculous sequelae, and bronchiectases. Segmentectomies are also indicated in the management of lung cancer patients with marginal cardiopulmonary function. However, irrespective of patient’s cardiopulmonary reserves, segmentectomies are also being increasingly used to resect small-sized (<2 cm) primary lung cancers and metastatic deposits from extrathoracic malignancies, with the aim of sparing lung parenchyma albeit maintaining compliance to the principles of oncologic radicality. In a recent series including 785 patients reported by Schuchert et al., 86% of the segmentectomies had been done for lung cancer. In particular, it has been suggested that for the noninvasive adenocarcinoma histologic subsets and ground-glass opacities with a solid component greater than 25%, segmentectomy can be a reliable alternative to lobectomy. In addition, segmental resections can be used both for bilateral benign and malignant lesions aiming at eradication of the disease, either malignant or benign. Conversely, tumor size crossing the segmental plane, unclear margins at frozen section, incomplete intersegmental nodal clearance, and presence of additional nodules in the same lobe represent contraindications to segmentectomy.
PREOPERATIVE PLANNING
As a rule, chest CT is obtained for lung cancer staging or to precisely localize the infectious lesion. The adjunct of PET is valuable for nodule characterization only if the lesion is larger than 8 mm to fall within PET resolution capability. Pulmonary lesions are detected with increasing frequency at low-dose CT scan done for lung cancer screening in high-risk patients. Preoperative planning should take into consideration the presence of histotypes with low metastatic potential (former bronchoalveolar carcinomas and carcinoids), previous lung resections on the same or the contralateral side, cardiopulmonary reserves, and technical feasibility of a segmentectomy with regard to the size of the nodule and its location compared to the intersegmental plane. Also, in the event of segmentectomy for primary T1N0 NSCLC, a safe tumor-free margin must be anticipated, i.e., greater than the diameter of the lesion or 2 cm. Recently, the use of highly sophisticated 3D CT scan reconstructions in outlining safe margins prior to segmentectomy has been reported.
SURGERY
Superior (S6) Right Lower Lobe Segmentectomy
Generalities
Under general anesthesia, the patient is placed on a left lateral decubitus and on one lung ventilation. The right chest is prepped and draped for either a posterolateral or a muscle-sparing thoracotomy. Upon entering the chest, the lobe is prepared as for right lower lobectomy. The division of the pulmonary ligament allows for isolation of the inferior pulmonary vein, which is dissected in the subadventitial plane and then encircled.
Segmental Hilar Dissection
A Kittner is used to sweep the adventitia off the main venous trunk distally onto the segmental branches, the most cranial of which is usually the vein from the apical segment (V6). At this point, V6 is encircled and stapled or doubly ligated.
The attention is then turned to the arterial supply to the lower lobe. In particular, the artery to the apical segment of the lower lobe (A6) can be approached inside the fissure and/or from the posterior mediastinal side (Fig. 23.1). In the fissure, the basilar artery is usually identified at the cross between the lower and middle lobes. Once in the subadventitial plane, the dissection is carried out cranially to identify the middle lobe artery and, opposite to it, A6. At this point, it is useful to divide the posterior part of the major fissure (Fig. 23.2). To this purpose, the space between A6 and the ascending posterior artery to the upper lobe is visualized. The tip of a right-angle clamp is engaged in this space and directed posteriorly toward the interbronchial angle between the right upper lobe bronchus and the bronchus intermedius until the posterior mediastinal pleura is entered (Fig. 23.2). Following this same route, a stapler is inserted and fired so as to expose A6.
The artery to the superior segment of the lower lobe (A6) is dissected, doubly ligated, and divided or stapled. This maneuver uncovers the bronchus to S6 (B6), which is carefully dissected and either divided and oversewn or stapled (Figs. 23.2 and 23.3). If the S6 segmentectomy is being performed for an infected segment, the bronchus should be divided first to avoid spillage of purulent secretions with lung manipulation.
Figure 23.1 Identification of the artery to the superior segment of the right lower lobe (A6), which is ligated and divided. Also visualized is the basilar artery. S6, superior segment.
Figure 23.2 The superior segment is rotated anteriorly to demonstrate the divided bronchovascular structures of the superior segment. A clamp is placed on the distal segmental bronchus to prepare for subsequent development of the intersegmental plane. S6, superior segment; B6, bronchus to the superior segment; A6, artery to the superior segment; V6, vein from the superior segment.
The Intersegmental Plane
The rare presence of an additional fissure separating S6 from the remaining segments (identifying the so called “Nelson,” “Devé,” or “Fowler” lobe) will facilitate the creation of an intersegmental plane. However, as a rule, the collapsed lung is cautiously reinflated thus outlining the intersegmental plane by contrast with the atelectatic S6 segment (Fig. 23.3). Alternatively, to improve visualization of the intersegmental plane, a reverse inflation–deflation technique can be used or dye can be injected in the closed distal segmental B6 bronchus. The intersegmental plane is characterized by the presence of an intersegmental vein draining S6 (Fig. 23.4). This vein should be respected when the intersegmental plane is created. However, small venous S6 branches to the intersegmental vein become visible as the intersegmental plane is developed (Fig. 23.4). Interruption of these small S6 venous branches is effected by stapling the intersegmental plane and/or by using electrocautery or energy devices on the individual branches. It must be kept in mind to place the line of resection proximally to the intersegmental vein to spare it while developing the intersegmental plane. Conversely, some authors describe distal stapling to the intersegmental vein (so called “extended segmentectomy”) to avoid postoperative bleeding from the raw intersegmental plane and increase tumor-free margin. The latter has been described as the only method to control segmental venous drainage without identifying, ligating, or stapling the correspondent segmentary venous trunk at the origin from the inferior vein (i.e., V6 or the basilar veins).
Figure 23.3 Inflation–deflation technique leading to the demarcation of the superior segment. S6, superior segment; B6, bronchus to the superior segment; A6, artery to the superior segment; V6, vein from the superior segment.
Figure 23.4 Development of the intersegmental plane by identifying and respecting the intersegmental vein; peeling technique (left upper corner). B6, bronchus to the superior segment; ISV, intersegmental vein.
A specific technique for separating the resected segment from the remaining lung consists of “peeling” this segment off the adjacent lung tissue (Fig. 23.4). A Duval or a Klemmer clamp is applied on the distal segmental artery (i.e., A6) and bronchus (i.e., B6) (Fig. 23.3). A gentle traction is exerted on the clamp with the right hand while the left hand is placed around the resected segment and the remaining lobe is ventilated by the anesthesiologist (Fig. 23.4). The small tributaries to the intersegmental vein are identified and coagulated as the left thumb is pushed toward the index finger to develop the intersegmental plane by thinning the intervening parenchyma (Fig. 23.4).
Basilar Right Lower Lobe Segmentectomy
Nowadays, although technically feasible, individual segmentectomies of the basilar segments are rarely done for lung cancer. In this chapter, the basilar segments are considered as one anatomosurgical entity since—apart for the treatment of bronchiectases—they are often resected together. In particular, the numerous anatomic anomalies of the bronchovascular structures of the infracardiac segment (S7) make resection of this segment technically challenging and, at times, impossible. In these circumstances, the benefits of pursuing the individual resection of S7, S8, S9, or S10 segments need to outweigh the risks of postoperative complications and contaminated margins.
The inferior pulmonary vein is encircled and the three basilar veins recognized as caudal to V6 are divided. Once the artery to the right lower lobe is identified in the fissure, care is taken to dissect free and respect A6. The basilar artery is therefore identified and doubly ligated or stapled. This maneuver discloses the basilar bronchus, which is dissected distal to the B6 take off and divided. By grasping the arterial and bronchial distal stumps the intersegmental plane between S6 and the basilar segments can be developed in a reverse fashion with regard to the intersegmental plane compared to S6 segmentectomy. Alternatively, a stapler can be applied to separate the basilar segments from S6.
Completing Surgical Maneuvers
To avoid torsion, the residual segment should be tacked to the remaining parenchyma. As an example, in the event of basilar segmentectomy, suturing of the remaining S6 to the posterior segment of the upper lobe is advised.
Hilar (i.e., segmental, lobar, and interlobar) and mediastinal lymphadenectomies are performed as a standard part of the procedure for lung cancer. Intraoperatively, exfoliation cytology of the stapled intersegmental plane may be analyzed for safe tumor-free margins. If developed by peeling, the intersegmental plane should be carefully checked for air leaks. Adequate measures should be adopted, from fine suturing to sealants or parietal pleural flap apposition on the raw parenchymal area. If the intersegmental plane is developed with staplers, buttressing may be needed in patients with advanced emphysema. As to the bronchial stump after segmentectomy for bronchiectasis, preventative coverage is not routinely performed. As a rule, one chest drain is left at the end of the procedure; it is left to the individual surgeon whether to cut an additional hole in the chest tube to help draining the basal space. If the right lower lobe segmentectomy is performed for infectious disease, the need to place another basal chest drain should be discussed as well as the drain removal policy to avoid residual spaces.
POSTOPERATIVE MANAGEMENT
After segmentectomy for lung cancer, an intermediate level of care is usually indicated. Drainage suction is evaluated based on the individual patient and institutional protocols but water seal should be instituted as early as possible. Also, an effort should be done to achieve early mobilization; in this setting, several surgeons prefer discharging the patient on a Heimlich valve if prolonged (i.e., longer than 5 days) air leaks are observed. If segmentectomy is performed for bronchiectasis, sensitivity oriented antibiotics may be administered for at least 5 days and physiotherapy focused on postural drainage administered until discharge.
COMPLICATIONS
Jones et al. reported a 39% overall morbidity rate after segmentectomy. In accordance with other investigators, the most common complications observed after open segmentectomy were atelectasis/pneumonia (14% to 16%), postoperative air leak (8% to 16%), and atrial fibrillation (9% to 10%). Besides aggressive physiotherapy, bronchoscopic clearance should be sufficient to reduce the likelihood of postoperative atelectasis/pneumonia. Reportedly, blood loss after segmentectomy is rarely greater than 100 mL. Significant postoperative bleeding requiring reoperation is rare usually resulting from the venous stump, ancillary procedures such as pleural tent or flap to cover the bronchial stump, or from torsion of the remaining segment. In the latter circumstance, completion lobectomy is performed. The development of an empyema mandates a more adequate drainage and obliteration of the pleural cavity. In the modern literature, the reoperation rate is reported to be as high as 5%. Furthermore, the median postoperative length of stay is 6 days. After open segmentectomy, the perioperative mortality was reported in the range between 0.9% and 3%, thereby reflecting the high-risk patient category subjected to this procedure.
RESULTS
Functional Outcomes
Medium and long-term functional results are favorable. According to the Mayo Clinic, 0.20 L of FEV1 is lost after segmentectomy. In the University of Pennsylvania Medical Center (UPMC) experience on 785 patients, a 3% and 12% decline in FEV1 and DLCO within 1 year of surgery, respectively were observed. All in all, after segmentectomy, 90% of preoperative function is preserved making this procedure suitable for use in both synchronous and metachronous lung lesions associated or in alternative to lobectomy.
Oncologic Outcomes
The Mayo Clinic reported their results with open segmentectomy on 113 patients operated on for non small cell lung cancer (NSCLC) during a 5-year period. About 20% of these segmentectomies were superior or basilar segmentectomies of the right lower lobe. Overall, the 5-year survival rates for patient with stage IA and IB were 79% and 46%, respectively. No difference in survival was observed with respect to histology and resected segment whereas, on multivariate analysis, the only adverse prognosticator was tumor larger than 2 cm. Recurrent disease was observed in 39 patients (34%), however, only 7% were local recurrences with more than 500 days of median time to recurrence. An additional 8% of the 113 segmentectomy patients developed simultaneous local and distant relapse whereas 19% of the patients were observed with distant recurrences only.
Open Versus VATS
Schuchert et al. from UPMC reported on their series of 225 patients undergoing either open or VATS segmentectomy. Of these, 19% were superior or basilar right lower lobe segmentectomies. Perioperatively, there was no difference between open and VATS in terms of blood loss and operative time. The length of hospital stay and pulmonary morbidity were 7 days and 30%, respectively, and differed significantly from the VATS procedures (5 days and 15%, respectively). Major and minor morbidity rates were not significantly different between open and VATS segmentectomies. However, the number of resected nodes varied significantly favoring the open over the VATS segmentectomy group (nine nodes vs. six). Of 225 patients from UPMC, 46 patients (20%) developed recurrent disease; of these, almost 40% were locoregional relapses. No statistically significant differences were seen between open and VATS segmentectomy in terms of both recurrence-free and overall survival rates.
CONCLUSIONS
In the tuberculous era as well as in the current one characterized by the “oncogenic addiction,” right lower lobe segmentectomies are useful procedures, which add to the armamentarium of the modern thoracic surgeon. In particular, the most recent views on lung cancer management and the reduced cutoffs for operability in an increasingly elderly population will likely contribute to the need of mastering these techniques to improve the clinical expertise of younger generations of thoracic surgeons.
Recommended References and Readings
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