Thoracoscopic S⁸ segmentectomy

S⁸ segmentectomies are indicated for some cT1a non-small cell lung cancers (NSCLCs) for patients who had undergone a previous major pulmonary resection and/or have a compromised pulmonary function and/or who present with two synchronous or metachronous tumors. It can also be proposed for some solitary metastases (Figure 1).

Figure 1 Metastasis from a colonic carcinoma in left segment 8.

S⁸ segmentectomies are slightly easier on left side compared to right one because there is no S⁷ segment (Figure 2). Variations in the distribution of arteries and bronchi require a thorough examination of preoperative modelisation. In this article, we will base on the most frequent anatomical pattern, that is A⁸ and a A⁹⁺¹⁰ common arterial trunk with the corresponding B⁸ and B⁹⁺¹⁰ bronchi (Figure 3).

Figure 2 Three-dimensional modelisation of right segments 8 and 7 (lateral view).

Figure 3 Anatomical landmarks. (A) B⁸ bronchus (front view); (B) A⁸ artery (front view); (C) V⁸ veins. Note that the posterior branch of the superior basal vein (V^8a) drains S⁹ and must be preserved.

Anatomical landmarks

In most cases, the basilar arterial trunk branches in two arteries: A⁸ and A⁹⁺¹⁰ (1). This pattern is more frequent on the right side (90%) than on the left side (74%). In a minority of patients, the anatomy is reverse with the following distribution: A⁸⁺⁹ and A¹⁰ (8% on the right side and 16% on the left side) (Figure 4). On the left side all three arteries can be independent (10%) (1). All arteries to the lower lobe must be clearly identified in order to avoid misidentification, such as a low A^8a being mistaken for an A⁹⁺¹⁰. When in doubt during dissection, it is advisable to control only the anterior branch of A⁸ (A^8b), then the bronchus and eventually check the direction of the second branch. An important variation deserves to be known: on the right, A⁷ is lacking in 16% of the patients, explaining why A⁷ is sometimes not found, even after an extensive dissection of the PA branches. When present, it is discovered on the posterior aspect of the arterial basilar trunk at a variable level between the onset of the middle lobe artery and the basilar arteries (Figure 5).

Figure 4 Anatomical variation of the branching of bronchi and arteries: common bronchial B⁸ and B⁹ trunk, and common arterial A⁸ and A⁹ trunk.

Figure 5 Dissection of the basilar segmental arteries. (A) Overall view; (B) identification of A⁷ (right). ML, middle lobe.

The basilar bronchial trunk usually separates in two branches: B⁸ and B⁹⁺¹⁰ which lie posterior to the segmental arteries. As for arteries, instead of a common B⁹⁺¹⁰ trunk, B⁹ can have a common birth with B⁸ (Figure 4).

The venous drainage is highly variable. The superior basal vein (SBV), which is the middle root of the IPV, does seldom represent the venous drainage of segment 8. Its posterior branch can drain segment 9 (Figure 3C). Actually, in most cases (88%), the inferior pulmonary vein has two tributaries: a V⁶ and a common basilar vein. If is thus safer to control the vein within the parenchyma and divide only the anterior branch of the vein (V^8b) which runs immediately behind the bronchus, rather than controlling V⁸ centrally in the inferior pulmonary vein.

Surgical technique

The basic principles of our technique have been described (2), as well as the need for preoperative modelisation (3).

Opening the fissure and controlling the artery

This step is similar to the dissection of the fissure during a lower lobectomy or a basilar segmentectomy. But the dissection of arteries must be pursued as low as possible and all branches to the lower lobe must be clearly identified.

Both A⁸ and A⁹⁺¹⁰ are looped (Figure 6), so that one can retract them forward or backward to expose B⁸. Dissection must be pursued on a sufficient length to detect any anatomical variation such as a lingular artery raising from A⁸ (Figure 7). A⁸ is clipped. All lymph nodes located in the arterial division must be dissected, removed and sent for frozen section (Figure 8). If invaded, the procedure should be extended, either to a basilar segmentectomy or even a lower lobectomy in patients operated for NSCLC.

Figure 6 Dissection and retraction of the basilar trunk in a patient with a common A⁸–A⁹ arterial trunk (left).

Figure 7 Example of a low birth of a lingular artery, at the same level as A⁸. LUL, left upper lobe; LLL, left lower lobe.

Figure 8 Dissection of intersegmental lymph nodes that are examined intraoperatively (left).

On the right side, a middle lobe artery can raise from A⁸ and similarly on the left side a lingular artery can raise from A⁸. This stresses the need for an extensive dissection of all arterial branches in the fissure (Figure 9).

Figure 9 Dissection of A⁸ artery arising from the lingular artery (4). Available online: http://www.asvide.com/article/view/27167

Dissecting and controlling the bronchus

By retracting B⁹⁺¹⁰ backward, B⁸ is exposed (Figure 10). It is carefully dissected to avoid any tear of the vein (V^8a) that runs just behind it. It is then stapled after a reventilation test.

Figure 10 Division of A⁸ exposes B⁸ and B⁹: (A) right side; (B) left side. A⁸s, stump of A⁸.

Dissecting and controlling the vein

There is no need to dissect the inferior pulmonary vein (1,5). Once the bronchus has been stapled, its stump is gently lifted up and its backside is denuded with caution to expose the anterior branch of the vein (V^8b). Its posterior branch (V^8a), that partially drains S⁹, is preserved (Figure 11).

Figure 11 Elevating the stump of B⁸ exposes the vein. Only it most anterior branch (V^8b) is divided (left).

Intersegmental plane

The intersegmental plane is determined by systemic injection of indocyanine green (ICG) at the dose of 0.3 mg/kg with fluorescence imaging system (Novadaq™) (6). Cautery dots are made on the parenchyma on this demarcation line, i.e., the plan between S⁸ and S⁹.

A long clamp is applied on the parenchyma, following the cautery spots that have been applied. It is checked that the bronchial stump stays remote and will not get stuck within the stapler jaws. The conic shape of S⁸ can make precise application of the stapler difficult with a risk of plication of the parenchyma. Thanks to use of two grasping forceps, the parenchyma can be stretched to expose the whole segment 8 and ease stapling.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editor (Alessandro Brunelli) for the series “Uncommon Segmentectomies” published in Journal of Visualized Surgery. The article has undergone external peer review.

Conflicts of Interest: The series “Uncommon Segmentectomies” was commissioned by the editorial office without any funding or sponsorship. DG is consultant for an instrument manufacturer (Delacroix Chevalier). The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this manuscript and any accompanying images.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

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