Uniportal video-assisted thoracoscopic isolated S4 segmentectomy of left upper lobe: a stepwise surgical technique

Introduction

Background

Anatomical segmental resection is increasingly applied in thoracic surgery for peripheral tumors ≤2 cm, as supported by recent randomized trials (JCOG0802, CALGB, a European phase 3 trial (1-3). Segmentectomy preserves lung parenchyma while maintaining oncologic outcomes comparable to lobectomy in selected early-stage NSCLC but demands advanced technical skill to navigate the sublobar broncho-vascular axis and to secure adequate resection margins.

Segmentectomies are also applied in the context of pulmonary metastasectomies, and for patients with limited respiratory reserve.

Resections of the lingula commonly involve both S4 and S5 because this approach is technically more straightforward. Isolated S4 segmentectomy preserves additional uninvolved S5 parenchyma, although the magnitude and clinical relevance of any functional benefit compared with S4+5 bisegmentectomy have not been established. Therefore, isolated S4 resection should not be considered routinely superior to lingular bisegmentectomy, but may represent an anatomical parenchyma-sparing option when the lesion is clearly confined to S4 and an adequate resection margin can be achieved

Rationale and knowledge gap

Isolated S4 segmentectomy poses unique challenges: segmental broncho-vascular structures are often deep and variable, increasing the risk of misidentification and intraoperative complication, and accurate delineation of the intersegmental plane is technically demanding. Although uniportal video-assisted thoracoscopic surgery (UVATS) has been widely adopted for many minimally invasive thoracic procedures, detailed descriptions of uniportal isolated S4 segmentectomy including stepwise strategies for hilar exposure, bronchial localization, control of deep arterial branches, and adjunctive plane-identification techniques [bronchoscopic selective inflation and indocyanine green (ICG) fluorescence], remain limited in the literature.

Isolated S4 segmentectomy is nonetheless technically feasible with adequate anatomical and manual experience by the operator.

Objective

This video and accompanying report describe a UVATS technique for anatomical resection of the superior lingular segment (S4), intraoperative bronchoscopic guidance, stepwise hilar dissection and management of deep segmental vessels, ICG-guided intersegmental plane delineation, and lymphadenectomy, through the use of various tools and maneuvers. We present the case and technique to provide practical and reproducible technical guidance for surgeons performing isolated S4 segmentectomy, with particular emphasis on bronchovascular identification, intersegmental plane delineation, and the limitations related to patient selection and oncological margin requirements. We present this article in accordance with the SUPER reporting checklist (available at https://jovs.amegroups.com/article/view/10.21037/jovs-2026-0051/rc).

Preoperative preparations and requirements

A 40‑year‑old female, non‑smoker, with exercise‑induced asthma (currently untreated), was investigated by chest computed tomography (CT) in late 2022 for an upper respiratory tract infection and found to have a stable 10-mm solid nodule in the left upper lobe (lingula, segment 4) (Figure 1). PET‑CT demonstrated no pathological uptake at the nodule or elsewhere. The nodule had remained radiologically stable for 1 year and was round, well circumscribed, and without pathological fluorodeoxyglucose (FDG) uptake. Although these features were not strongly suggestive of invasive primary lung malignancy, the exact nature of the lesion remained uncertain. The patient was particularly anxious about continued radiological surveillance and, after multidisciplinary discussion and shared decision-making, expressed a clear preference for surgical diagnosis. Because the lesion was confined to S4 and located sufficiently deep to make a wedge resection less suitable, an isolated S4 segmentectomy was selected. Preservation of S5 was considered anatomically feasible; however, the choice was not based on impaired pulmonary reserve or on an expectation of a proven functional advantage over S4+5 resection.

Figure 1 Axial (A) and sagittal (B) view of chest CT scan. Identification and localization of the nodule in front of bronchus B4. CT, computed tomography.

Preoperative preparation included routine cardiopulmonary assessment and optimization for anesthesia (planned single‑lung ventilation with a right double‑lumen endotracheal tube). The patient benefited, like all anatomical resections at our hospital, from an enhanced recovery after surgery (ERAS) program including preoperative counseling, anemia management, venous thrombosis prophylaxis, and preoperative carbohydrate loading.

Perioperative prophylactic antibiotic (cefuroxime 1.5 g) was given according to institutional protocol. The patient received standard preoperative counseling regarding the UVATS approach, the potential need for intraoperative conversion to thoracotomy, and possible complications.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article, the accompanying images and the video. A copy of the written consent is available for review by the editorial office of this journal.

Step-by-step description

General anesthesia is administered and ventilation is provided via a right double-lumen endotracheal tube. The patient is placed in a right lateral decubitus position, and the surgical table is angled (about 30°) to enhance the intercostal space. An incision measuring 4 cm is made in the 5th intercostal space, strategically located between the scapular tip and the breast along the anterior axillary line. The incision is protected using a soft-tissue plastic retractor (Alexis XS, Retractor, Applied Medical, Rancho Santa Margarita, CA, USA).

The surgical team, consisting of the surgeon and the assistant, is positioned anteriorly to the patient, while the scrub nurse is at the rear. Visualization of the pleural cavity and the surrounding mediastinal structures is optimized with a 10-mm 30° Endoeye thoracoscope (Olympus, Tokyo, Japan). For dissection and coagulation, a dissector (Scanlan International, St Paul, MN, USA), a hook monopolar cautery, and an ultrasonic device (HARMONIC^® Endo Surgery, Inc., Cincinnati, Ohio) are utilized. All vessels are transected using endoscopic staplers (EndoGIA, Medtronic, Minneapolis, MN, USA).

The mediastinal pleura is opened using the HARMONIC^® energy device, providing immediate visualization of the venous trunk supplying the left upper lobe (Video 1). Dissection then progresses cranially, freeing the left main arterial trunk. Subsequently, dissection is deepened within the parenchyma between the anterior segment and the lingula, following the venous branch destined for S4. Beneath the venous axis, the bronchus to the lingula is identified and mobilized at both its cranial and caudal ends.

First, the lingular bronchial branches are exposed. Intraoperative bronchoscopy is then performed to distinguish B4 from B5 before any irreversible bronchial division. Bronchoscopic confirmation is particularly useful in this deep hilar location, where the segmental bronchi may be closely related and difficult to differentiate by external dissection alone. After confirmation, the cranial B4 branch is transected using a curved-tip stapler. Elevation of the bronchial stump reveals a second posterior B4 branch, which is again confirmed anatomically and subsequently divided with a curved-tip stapler.

Dissection is then continued distally along the bronchovascular axis, allowing progressive exposure of the deeply situated arterial branches supplying S4. Two arterial branches, A4a and A4b, are identified. A4a is sufficiently exposed and accessible to permit safe stapler placement and is divided using a curved-tip vascular stapler. In contrast, A4b is smaller and located deeper within the parenchyma; rather than forcing a stapler into a confined space, it is controlled by ligation and coagulation using the ultrasonic device.

After division of the segmental bronchovascular structures, the intersegmental plane is identified following intravenous injection of indocyanine green (0.1 mg/kg). The plane between S4 and the adjacent preserved segments is then divided using 45- and 60-mm stapler reloads. If the bronchovascular anatomy cannot be confidently defined, an adequate parenchymal margin cannot be achieved, or the intersegmental plane cannot be reliably identified, isolated S4 segmentectomy should not be pursued and extension to S4+5 segmentectomy or another anatomical resection should be considered.

The specimen was submitted for intraoperative frozen-section examination, which raised suspicion of a neoplastic lesion but did not establish a definitive diagnosis of NSCLC. This finding was considered in the context of preoperative imaging, which showed a small, round, well-circumscribed nodule without FDG uptake and without documented interval growth. Because the pathological findings were therefore discordant with the radiological phenotype, and because malignancy remained unconfirmed, we proceeded with systematic hilar and mediastinal lymph-node dissection but deferred extension of the pulmonary resection pending definitive histology. Final pathological examination demonstrated a 1.2-cm sclerosing pneumocytoma with a closest parenchymal margin of 5 mm. Finally, an intercostal nerve block (bupivacaine 0.5%) is administered between the 2nd and 8th intercostal spaces. A 28-French (Fr) chest tube is placed, and the lung is re-expanded under direct visualization. Total operative time was 170 minutes.

Postoperative considerations and tasks

The postoperative course was uneventful, with pleural drainage removed on the first postoperative day, and the patient was discharged on the third day. The histopathological analysis, contrary to the frozen section findings, did not reveal any malignancy but instead showed a lesion consistent with a sclerosing pneumocytoma, measuring 1.2 cm, a rare and benign epithelial lung tumor. Importantly, this 5-mm margin would not have been considered adequate had NSCLC been definitively diagnosed. In that situation, extension to an S4+5 segmentectomy or left upper lobectomy would have been required to achieve an appropriate parenchymal margin. This discordance between frozen section and final histology, and its practical consequences, is discussed further below. At 1-month follow-up, no postoperative complications were observed.

Tips and pearls

The following points are intended as decision-level guidance that complements, rather than repeats, the step-by-step description above.

• Multidisciplinary team and patient selection: involve thoracic surgeons, anesthesiologists and interventional bronchoscopy staff preoperatively. Consider patient age, comorbidities, pulmonary reserve, tumor size/location (peripheral ≤2 cm ideal) and surgeon’s uniportal experience when planning isolated S4 segmentectomy.
• Bronchial identification: because B4 and B5 may be closely related and anatomically variable, the bronchial branches should be clearly exposed before division. Intraoperative bronchoscopy is particularly useful when the anatomy is uncertain and should be repeated before bronchial transection if there is any doubt regarding B4/B5 identification.
• Deep arterial branches: the A4 branches are often located deeply within the parenchyma. Progressive dissection along the bronchovascular axis facilitates safe exposure. Stapling should be reserved for branches that can be safely encircled and accommodated within the stapler jaws. Smaller or deeper branches, as with A4b in the present case, may be more safely managed by ligation and/or energy-based coagulation.
• When to extend the resection: isolated S4 segmentectomy should not be pursued at the expense of safety or oncological adequacy. Extension to S4+5 segmentectomy or another anatomical resection should be considered when the bronchovascular anatomy remains uncertain, an adequate parenchymal margin cannot be achieved, bleeding cannot be safely controlled, or the intersegmental plane cannot be reliably identified.
• When frozen-section examination is suspicious but non-diagnostic for malignancy, the degree of pathological certainty should be interpreted together with preoperative imaging and parenchymal margin assessment. If NSCLC is confirmed, both appropriate lymph-node staging and an adequate parenchymal margin are required, and extension of pulmonary resection should be considered when these oncological criteria are not fulfilled
• Postoperative analgesia and recovery: perform an intercostal nerve block (e.g., bupivacaine 0.5%), use a single 28-Fr drain as indicated, and aim for early mobilization and chest-drain removal to shorten length of stay.

Discussion

We describe a reproducible, stepwise UVATS technique for isolated anatomical resection of the superior lingular segment (S4), combining hilar-first dissection, intraoperative bronchoscopic bronchial localization, and ICG-guided intersegmental plane delineation, with specific strategies for the deeply situated A4 branches.

Most reported lingular resections address segments 4 and 5 together, largely because a fissural or combined approach to the two arterial and bronchial branches is technically more straightforward than isolating S4 alone (4,5). Isolated S4 segmentectomy is described far less often, and the available literature offers limited procedural detail on the specific difficulties it raises: the segmental vessels lie deeper within the parenchyma than in most other segmentectomies, and the arterial supply to the lingula is anatomically variable, with the artery occasionally found in a pre-bronchial position. In the present case, preoperative planning was based on conventional CT imaging, as dedicated three-dimensional (3D) reconstruction software was not available in our department at that time. Nevertheless, given the variability of the lingular bronchovascular anatomy, contemporary 3D reconstruction may provide useful additional information when available.

The rationale for isolated S4 segmentectomy deserves particular consideration because the additional amount of preserved parenchyma compared with S4+5 bisegmentectomy is limited. In the present patient, preservation of S5 was not required because of impaired pulmonary function, and we cannot infer a clinically meaningful functional benefit from this single case. Rather, isolated S4 segmentectomy was selected because the lesion was anatomically confined to S4 and preservation of uninvolved S5 parenchyma was technically feasible. Accordingly, the potential benefit of additional parenchymal preservation must be balanced against the greater technical complexity of isolated S4 resection, and S4+5 bisegmentectomy remains an appropriate alternative when anatomical or oncological considerations favor a wider resection.

Once the arterial branches to S4 have been accurately identified, the intersegmental plane between segments 3 and 5 is relatively linear, which facilitates secure and reproducible stapling. ICG fluorescence is a valuable adjunct at this step, as it clarifies the vascular anatomy and supports precise delineation of the intersegmental boundary; however, it is not infallible, and bronchoscopic confirmation remains the more direct safeguard against bronchial misidentification when ICG findings are equivocal (6).

The intraoperative course in this case also illustrates a separate, non-technical challenge: frozen section over-called a benign sclerosing pneumocytoma as suspicious for malignancy, leading to a formal lymphadenectomy that, in retrospect, was not oncologically required. Frozen section has known limitations in small peripheral nodules with atypical but benign histology, and sclerosing pneumocytoma is a recognized mimicker. This does not represent a technical failure of the segmentectomy itself, but it is a clinically relevant consideration for surgeons performing sublobar resections on frozen-section guidance, and it argues for cautious interpretation of equivocal frozen results in this specific setting rather than automatic escalation.

The intraoperative decision-making in this case was influenced not only by the frozen-section findings but also by their discordance with the preoperative radiological characteristics of the lesion. The nodule was small, round and well circumscribed, showed no FDG uptake, and had remained radiologically stable, features that were not strongly suggestive of an invasive primary lung malignancy. Frozen section raised suspicion of a neoplastic lesion but did not definitively establish NSCLC. In this context of diagnostic uncertainty, lymph-node dissection was performed because malignancy could not be excluded, whereas additional pulmonary resection was deferred pending definitive pathological assessment. Nevertheless, the final benign diagnosis should not retrospectively be used to justify the extent of resection. The closest pathological margin was 5 mm, which would not have been considered adequate for an intentional oncological segmentectomy for NSCLC. Had malignancy been definitively established intraoperatively, extension to S4+5 segmentectomy or lobectomy would have been indicated.

The main strength of this report is the level of technical detail provided for a resection that is infrequently described in isolation, including explicit strategies for deep vessel control and plane identification. The main limitation is that it is based on a single case, performed by an experienced uniportal surgeon; reproducibility by surgeons earlier in their uniportal learning curve, and the technique's oncologic equivalence to bisegmentectomy or lobectomy over the longer term, remain to be established by comparative outcome data.

Uniportal isolated S4 segmentectomy is technically feasible in carefully selected patients in whom the lesion is confined to S4 and adequate margins can be achieved. Its potential advantage lies in preservation of uninvolved S5 parenchyma; however, a clinically meaningful functional benefit over S4+5 bisegmentectomy has not been established, and this limited parenchymal gain must be balanced against the greater technical complexity of the procedure. The role of isolated S4 segmentectomy should remain limited to carefully selected cases in which the anatomical and oncological requirements of a limited resection can be fulfilled. The role of isolated S4 segmentectomy in malignant disease remains to be established and requires validation in comparative oncological studies.

Conclusions

Isolated S4 segmentectomy is a feasible and effective procedure via a thoracoscopic uniportal approach. With careful and diligent dissection and attention to bronchovascular anatomy, this method can successfully address localized lesions while preserving lung function.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the SUPER reporting checklist. Available at https://jovs.amegroups.com/article/view/10.21037/jovs-2026-0051/rc

Peer Review File: Available at https://jovs.amegroups.com/article/view/10.21037/jovs-2026-0051/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jovs.amegroups.com/article/view/10.21037/jovs-2026-0051/coif). M.G. serves as an unpaid editorial board member of Journal of Visualized Surgery from February 2026 to December 2027. The other authors have no 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 this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article, the accompanying images and the video. A copy of the written consent is available for review by the editorial office of this journal.

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/.

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