Initial experience of thoracoscopic segmentectomy of basal segment through the inferior pulmonary ligament approach in treating congenital lung malformations in children

The incidence of CLM is 1–4.2 per 10,000 [9]. The CLM primarily consists of CPAM and PS. For children with CLM having no obvious symptoms after birth, there is some controversy over whether to choose conservative observation or surgical resection [10]. Due to the risk of infection and malignant transformation associated with asymptomatic children, surgical treatment has been able to achieve low risk and low complications in managing CLM. Therefore, it is recommended to choose surgical treatment for asymptomatic CLM children [11].

Owing to the fact that CLM is a benign lesion, segmentectomy is a good choice for patients whose lesions are limited to the lung segment if the technical level is mature. Lung segments were divided into simple or complex segments. Simple segmental resection, similar to lobectomy, is a relatively simple and widely performed surgery. Complex lung segment resection is challenging because of the need to manage multiple segment planes. S10 Surgery is more challenging since it is far from the hilum of the lungs and adjacent to three or four lung segments [12, 13]. Segmentectomy through the hilar approach is currently the most commonly used method for S10 resection. This method can be used to achieve S10 segmentectomy; its drawbacks are undeniable. To expose the hilar of S10, the lower pulmonary artery, lower pulmonary bronchus, and their tributaries should be extensively freed, which is very traumatic. Moreover, the connection between S6 and the basal segment should be severed. After removal, S10, S6, and S7 (8) -9 are in a free state, increasing the risk of pulmonary torsion. Owing to the fact that the end of the pulmonary vein is close to the hilum of the lung, accurately distinguishing the inter-segment veins from the intra-segment veins is difficult while freeing the pulmonary vein from the end to the main trunk. It is easy to rupture inter-segment veins inadvertently, obstructing blood flow return [14]. Based on the characteristics of S10, some researchers have proposed an inferior pulmonary ligament approach for S10 resection. The deep surface of the inferior pulmonary ligament directly corresponds to the S10 segment gate, which can be rapidly released. The probability of lung torsion is reduced by maintaining the link between S6 and S7 (8) -9. The dissociation of branches from the main trunk of the lower pulmonary vein can easily expose intra-segmental and inter-segmental veins, which is beneficial for preserving the inter-segmental veins. Good surgical outcomes have been achieved (5–8). S10 segmentectomy is now rarely performed in children, and all procedures are performed through the hilar approach [4, 15]. Therefore, for lesions in S10, we perform segmentectomy via the inferior pulmonary ligament approach to explore the feasibility and limitations of this surgery for treating CLM in children.

Children have a smaller thoracic space than adults do, and an artificial pneumothorax is more likely to affect hemodynamics significantly. Therefore, establishing a suitable operating space is critical to a successful surgery. By combining an artificial pneumothorax with selective single-lung ventilation, we established a surgical operating space. During surgery, we found that the inferior pulmonary ligament approach made it easier to construct an operating area. Only one-lung ventilation in the lower lobe is required to obtain sufficient operating space because there is no need to consider the impact of the upper and middle lobes on the operating space after establishing an artificial pneumothorax and completing diaphragm compression. This significantly reduces the technical requirements for anesthesiologists and makes surgery easier. It is necessary to break the cysts to gain a larger space for patients with CLMs and large cysts [16]. CLM differs from lung cancer. This is because it is a benign cystic lesion requiring no surgical margin consideration. This only necessitates complete resection of the lesions. Is there a more suitable method for determining the inter-segment plane? The modified “dilation and collapse method,” whose purpose is to find the target segment bronchus is currently the most often used method for establishing the inter-segment plane [17, 18]. Owing to the fact that the target segment bronchus is relatively fixed in position, it can be found between V6 and V9 at the V10 deep surface after disconnecting V10 [5, 8]. Owing to the young age of children, the target bronchus is very small, the wall is very thin, and dissociation requires extra caution and time. The modified “dilation and collapse method” cannot be used to determine the inter-segment plane once the target segment bronchus ruptures. It is necessary to destroy the large cysts to obtain a wider operating space for children with CLM accompanied by large cysts. In this situation, using the modified “dilation and collapse method” to determine the inter-segment plane often yields poor results. In response to the limitations of the modified “dilation collapse method” in determining the inter-segment plane of the CLM children, we often combine the use of inter-segment veins for inter-segment plane determination. Intersegmental veins are natural boundaries between lung segments. The inter-segmental plane can be determined if accurately positioned and dissociated [19]. The tissues of children are loose, blood vessels are more prone to dissociation, and they bleed less, making them easier to operate. Preoperative 3D reconstruction is useful for surgical planning; however, it might be challenging to achieve good outcomes in children due to their small blood vessels. Therefore, 2D CT readings can be used to clearly define the venous route and plan surgery, requiring surgeons to have a good ability to read CT films [20]. Moreover, for surgeons with advanced CT film-reading ability, determining and dissociating the segmental veins (intra-segmental-and inter-segmental veins) is easy, and segmentectomy can be accomplished by the inter-segmental vein defining the inter-segment plane. In this group cases, we used the modified “dilation and collapse method,” supplemented by the inter-segmental vein to determine the inter-segmental plane, and successfully completed 14 cases of S10 resection. Cystic lesions are common in CLM, and the characteristics of cystic dilation can affect segmentectomy. In this study, we found that the deep surface of the lesion located in S10 penetrated the adjacent lung segment, pressing the deep tissue of the adjacent lung segment outward in children with CLM accompanied by large cysts. Further, when the lesion is entirely excised, the surrounding tissue of the adjacent lung segment is very thin and has a poor blood supply. Except for S10 segmentectomy, a partial wedge resection of the adjacent lung segment is often required. One child in this group was scheduled to undergo a segmentectomy of the right S10. The segmentectomy of the right S10 and partial wedge resection of the right S6 were performed due to the large cyst in the lesion penetrating the next lung segment. Air leakage is a common complication following segmentectomy, with severe cases leading to bronchopleural fistula [21, 22]. Only a few patients in this group experienced minor air leakage and subcutaneous emphysema, which quickly resolved after surgery. This is because surgery through the inferior pulmonary ligament does not involve the problem of managing a large airway. Hence, even if air leakage occurs when the target bronchus is properly treated, only the alveolar air leakage can self-close. We sutured the stump edge to reduce the risk of air leakage further.

Our center has achieved good short-term clinical outcomes in treating CLM using thoracoscopic segmentectomy of S10 via the inferior pulmonary ligament approach. However, the sample size of this study was small, and it was a single-center, retrospective study. Therefore, it will be necessary in later stages to further verify the feasibility and limitations of this surgical method in treating patients with CLM using large-sample, prospective, and multicenter studies. In this study, we found that there are challenges in determining the inter-segment plane and performing precise segmentectomy of S10 using only the modified “dilation and collapse method” for CLM with large cysts. Therefore, other surgical methods are more suitable for these patients. Some researchers have recently proposed surgical methods, such as “modified wedge resection” and “anatomical lesion resection.” Theoretically, the core of these surgical methods is to perform precise resection of the lesion via inter-segmental veins as the internal boundary and the natural boundary between the lesion and normal tissue as the external boundary, rather than being limited to precise segmentectomy [23, 24]. Therefore, it is worth exploring whether this surgical method is more advantageous in treating CLM with large cysts.