Applied Anatomy

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CHAPTER 4 Applied Anatomy

Cynthia S. Chin, Scott J. Swanson

Introduction

Anatomy of the thoracic cavity is constant regardless of the surgical approach, but the vantage point is different with the use of open surgery or minimally invasive surgery. When performing video-assisted thoracoscopic surgery (VATS), the surgeon must understand the anatomy as viewed from the videoscope and as seen through a thoracotomy. This chapter describes the techniques of exposure for the major anatomic structures in the thorax.

Right Upper Lobectomy

Anterior Hilum

♦ Exposure: Retract the lung posteriorly.

♦ Aim the thoracoscope anteriorly and medially.

♦ The phrenic pedicle travels in a superoinferior direction on the superior vena cava and heart (Figure 4-1). Identify this structure so that it is not inadvertently injured in dissection of the superior pulmonary vein (SPV) (Figure 4-2). Using blunt dissection, the phrenic nerve and its vessels can be swept anteriorly away from the pulmonary vein (Figure 4-3).

♦ The important structures are the SPV, which is most anterior; the right pulmonary artery, which is posterior and often superior to the SPV; and the right upper lobe bronchus, which is the most posterior structure and often can be identified after the SPV and the truncus anterior branch of the pulmonary artery are divided (Figure 4-4).

♦ With retraction of the lung inferiorly from the posterior incision, the azygous vein can be identified passing to the superior vena cava from a posterior direction (Figure 4-5). It is positioned just superior to the truncus anterior branch of the pulmonary artery and the right mainstem bronchus. It should be dissected bluntly away from these structures. Mobilizing the azygous vein allows complete node dissection (Figure 4-6). If there are any problems with visualization of the nodes, the vein can be readily divided with the endovascular stapler.

Figure 4-1 The right phrenic nerve crosses the first part of the subclavian artery as it enters the thoracic cavity. It travels along the superior vena cava as it goes inferiorly toward the diaphragm.

Figure 4-2 The right phrenic nerve courses closely to the right hilum. The right upper lobe is retracted posteriorly, and the phrenic nerve can be seen traveling across the superior pulmonary vein.

Figure 4-3 The right phrenic nerve is bluntly dissected from the superior pulmonary vein. Using two endokittners, the phrenic nerve can be swept away from the superior pulmonary vein to avoid inadvertent injury during ligation of the vein for a right upper lobectomy.

Figure 4-4 A, In the superior aspect of right anterior hilum, the superior pulmonary vein lies anterior to the pulmonary artery, which lies anterior to the bronchus of the right upper lobe. B, The anterior aspect of the right upper lobe bronchus can be visualized after the superior pulmonary vein and the truncus anterior branch of the pulmonary artery are ligated.

Figure 4-5 The azygous vein travels anteriorly at the level of the carina over the superior portion of the right hilum to join the superior vena cava. It is close to the right upper lobe bronchus and the truncus anterior branch of the pulmonary artery at this location.

Figure 4-6 Level 4R paratracheal nodes lay posterior to the confluence of the azygous vein and superior vena cava. Diseased lymph nodes may adhere to one or both structures, and care must be taken to avoid injury to these vessels. A, shows a lymph node anterior to vagus nerve. B, shows scar at junction of azygous vein and SVC.

Posterior Hilum

♦ Exposure: Retract the lung anteriorly.

♦ Aim the thoracoscope posteriorly.

♦ After opening the posterior mediastinal pleura with the harmonic scalpel or cautery device, you can see the subcarinal space with the right mainstem bronchus and bronchus intermedius traveling in an oblique direction toward the lung (Figure 4-7).

♦ The azygous vein travels up the posterior chest wall before turning anterior at the level of the carina (Figure 4-8). With gentle blunt dissection, free the vein from the right mainstem bronchus.

♦ During the subcarinal node dissection, the entire subcarinal space is well visualized. The esophagus lies anterior to the left mainstem bronchus (Figure 4-9). After the nodes are completely resected, hemostasis is straightforward and can be accomplished with surgical cellulose and pressure. Use thermal energy discretely to avoid injury to the membranous right mainstem bronchus or the esophagus.

♦ Sweeping mediastinal pleura up toward the lung permits visualization of the right upper lobe bronchus taking off at a 90-degree angle from the right mainstem bronchus (Figure 4-10).

♦ The thoracic duct lies posterior to the esophagus and is rarely an issue, although with extensive node dissection in the subcarinal space, significant thoracic duct radicals can be disrupted. Use clips on any lymphatic vessels of significant size (>2 mm).

♦ Extensive paratracheal node dissection extends to the apex of the right chest. Identify the right subclavian artery and vein (Figure 4-11). Avoid extensive thermal dissection in this region to avoid injury to the right recurrent nerve. Medially and anteriorly, the left innominate vein joins the right innominate vein to form the superior vena cava (Figure 4-12). It should be identified during the high paratracheal node dissection. The pericardium can be seen at the base of the paratracheal node dissection after the nodes are removed.

Figure 4-7 In the right subcarinal space, the right mainstem bronchus emerges from under the azygous vein just before the takeoff of the right upper lobe bronchus.

Figure 4-8 The azygous vein travels superiorly lateral to the right border of the thoracic vertebral bodies.

Figure 4-9 The left mainstem bronchus is visualized from the right hemithorax during dissection of the subcarinal space.

Figure 4-10 The right upper lobe bronchus (posterior aspect) is best visualized after the mediastinal pleura is swept toward the lung.

Figure 4-11 The right subclavian artery and vein can be seen in the apex of the right hemithorax.

Figure 4-12 The left innominate vein crosses the mediastinum to join the right innominate vein to form the superior vena cava.

Right Middle Lobectomy

♦ Exposure: Retract the lung posteriorly.

♦ Aim the thoracoscope anteromedially.

♦ The phrenic nerve courses in an inferior direction over the base of the middle lobe pulmonary vein (Figure 4-13). Similar to the dissection for the upper lobectomy, bluntly sweep away the nerve to avoid injury to it. The middle lobe pulmonary vein usually drains into the left atrium with the superior pulmonary vein but can drain separately or, rarely, with the inferior pulmonary vein. The middle lobe vein is composed of two segmental veins, with one anterior to the other or, less commonly, with one superior to the other.

♦ Unlike with the upper lobe, the bronchus sits posterior to the vein with the middle lobe pulmonary arteries posterior to the bronchus or slightly superior to the bronchus (Figure 4-14

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