Pneumonectomy
March 17, 2019

Segmentectomy (removal of an anatomic division of a particular lobe of the lung)

What id the Segmentectomy?

Minimally invasive pulmonary segmentectomy allows adequate oncologic treatment in selected cases while preserving lung parenchyma and minimizing perioperative morbidity and length of hospital stay.

Although several variations of minimally invasive pulmonary segmentectomy have been described, I favor a fully thoracoscopic multiport approach that allows direct access to the segmental structures, and is straightforward and versatile enough to allow adaptation (such as conversion to lobectomy in the case of positive margins) if there are unexpected intraoperative findings.

Key aspects of the procedure include proper patient positioning, appropriate positioning of operating trocars, standardized technique to expose and dissect the segmental vein, bronchus, and artery, and accurate division of the intersegmental plane and fissure.

Segmentectomy offers selected patients the possibility of an adequate oncologic treatment with preservation of pulmonary parenchyma and function, while minimizing perioperative morbidity and length of hospital stay, particularly when performed thoracoscopically [1-4]. Most segments may be resected individually or as part of bisegmentectomies (e.g. lingulectomy), although the basal segments may be particularly challenging.

We present a superior segmentectomy of the right lower lobe in a 73-year-old patient with a small indeterminate lesion that remained without a definite diagnosis despite percutaneous biopsy. Intraoperative frozen section raised the possibility of an adenocarcinoma of colonic origin. The patient did well and was discharged home on postoperative day one. Final pathology suggested a colonic metastasis and further postoperative investigations revealed an asymptomatic rectal cancer that had not shown up on the initial PET scan. The patient subsequently underwent proctectomy.

 Patient positioning and trocar placement

The patient is placed in a lateral decubitus position with the table generously flexed to move the patient’s hip out of the way and widen the intercostal spaces, which improves range of motion.

We use a posterior approach when performing a superior segmentectomy: the surgeon stands behind the patient and dissection proceeds from the back. This provides the most direct path to the anatomic structures at the base of the segment and simplifies the procedure.

We introduce the trocars in the following sequence:

First, a port inserted inferiorly is used for the camera throughout. It is placed somewhat posteriorly to the tip of the scapula, which improves visualization of the posterior aspect of the hilum. A 5-mm scope in optimal working condition provides excellent visualization. However, available 5-mm scopes are fragile and in our hospital setting deteriorate quickly with routine maintenance. For this reason, we prefer using a 10-mm scope.

Next, a 10-mm port is placed anteriorly and inferiorly. This is used for retraction and stapling of the bronchus and vessels. This port is also used for specimen extraction.

A 10-mm port is placed posteriorly and inferiorly and is used for dissection and parenchymal division.

A 5-mm port behind the scapula is used mainly for retraction.

Although endoscopic trocars may be used, we have found that they limit range of motion and we generally avoid them, except for the camera. Likewise, we have not found CO2 insufflation to be necessary.

Mediastinal lymph node dissection is generic to all oncologic pulmonary resections. However, as it is not specific to segmentectomy, it is not included in this tutorial.

 Lung mobilization

Mobilization of the lung begins with the division of the inferior pulmonary ligament. The inferior pulmonary vein is identified and dissected toward the parenchyma. The venous branch of the superior segment is found along the superior border of the inferior pulmonary vein.

The pleura overlying the posterior aspect of the hilum is divided superiorly to identify the origin of the bronchus intermedius. This is an important landmark for identifying the segmental bronchus and artery.

 Dissection and division of the segmental vein

Dissection of the superior segmental vein is completed and the vein is divided. A suture or vessel loop passed around the vein may be helpful with retraction and exposure.

 Division of the bronchus

Division of the segmental vein will give better access to the segmental bronchus, which lies deep and just superior to the vein, at the upper border of the bronchus intermedius.

Upward traction on the parenchyma will give the segmental bronchus a vertical path, at a 90˚˚  angle with the bronchus intermedius, making identification and dissection fairly straightforward.

Since segmental bronchi may be quite thin, caution should be exercised to avoid excessive traction or thermal injury during dissection. The artery lies deep in the bronchus and is hidden from view at this point in the procedure. Therefore one should ”hug” the bronchus with the right angle clamp and proceed with caution in order to avoid vascular injury.

Once dissected, the bronchus is divided using an endoscopic stapler. A small-caliber red rubber catheter is often useful to guide the anvil through the narrow space between the bronchus and the underlying artery.

 Division of the intersegmental plane and dissection of the artery

Bronchial division allows access to the segmental artery that lies deep and parallel to the bronchus. The segmental artery is dissected near its origin as the basilar artery is identified. While staying in a plane above the basilar artery, the intersegmental plane is divided from back to front, all the way to the oblique fissure. This requires careful positioning of the anvil, and guiding the parenchyma into the jaws of the stapler using graspers.

Although one may divide the artery first, dividing the intersegmental plane will often allow more comfortable access to the artery. Differential insufflation to more precisely delineate the intersegmental plane is somewhat tedious and generally unnecessary.

 Division of the fissure and completion of the resection

Division of the intersegmental plane is completed, all the way to the oblique fissure. Dissection is carried proximally under the parenchyma along the interlobar artery in order to completely mobilize the upper portion of the oblique fissure. The oblique fissure may then be divided, always making sure to position the anvil above the interlobar artery. The fissure and intersegmental staple lines are connected to complete the resection.

Outcome
Although oncologic outcomes associated with segmentectomy are the subject of debate, segmental resections may offer several advantages compared to lobectomy [1]. These include 1) parenchymal sparing, which is especially useful in patients with multiple pulmonary nodules as it increases subsequent therapeutic options in these patients; and 2) preserving pulmonary function and minimizing perioperative morbidity, including air leaks [2, 3]. These advantages are maximized when using a thoracoscopic approach [4].

Segmentectomy may also offer the possibility of obtaining a definitive tissue diagnosis for more central lesions, with minimal sacrifice of parenchyma.

In our experience of more than 40 cases, median chest tube drainage is required for 1 day and median hospital stay is 2 days; current mean operating times are around 2 hours (unpublished).

Discussion
Thoracoscopic segmentectomy requires familiarity with segmental anatomy and the operative approaches to the different segments. Most segments may be resected individually or as part of bisegmentectomies (e.g. lingulectomy) although the basal segments may be particularly challenging.

The optimal minimally invasive approach (VATS, uniportal VATS, completely thoracoscopic, robotic) remains the subject of debate [1]. We favor a completely thoracoscopic approach, which I find straightforward and versatile. For the superior segment of the lower lobes, a posterior approach offers direct access to segmental hilar structures (bronchus, artery). This facilities dissection and leaves the rest of the fissure and other tissue planes undisturbed in case further resections are required in the future.

There are several methods of delineating the intersegmental plane; differential insufflation after bronchial clamping or transection is cumbersome and generally unnecessary; if a precise anatomic definition is desired, indocyanine green fluorescence is a useful alternative [5].

In summary, thoracoscopic segmentectomy optimizes perioperative outcomes and is ideally suited to an enhanced recovery after surgery (ERAS) [1] approach. It also increases the surgeon’s armamentarium for dealing with either small low-grade tumors or complex cases of patients with multiple nodules and significant compromise of cardiopulmonary function.

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