Segmental Lung Resection

Anatomy and Physiology

The right lung consists of 3 lobes: the upper, middle, and lower. The left lung has 2 lobes: the upper and lower. Each lung contains 10 anatomic segments. Lung segments are defined by their segmental bronchi and associated vascular supply. Parenchymal segments are labeled as S#, bronchial anatomy as B#, pulmonary arterial anatomy as A#, and pulmonary venous anatomy as V#. 

Right Lung

• Upper lobe
  • The apical segment (S1) is the lung's most superior aspect and is defined by B1, A1, and V1.
  • The posterior segment (S2) incorporates the inferior posterior aspect of the upper lobe and is defined by B2, A2, and V2.
  • The anterior segment (S3) encompasses the inferior anterior aspect of the upper lobe and is defined by B3, A4, and V4.
  • These segments might be resected individually or together.
• Middle lobe
  • The lateral segment (S4) is at the middle lobe's posterior and lateral aspect and is defined by B4, A4, and V4.
  • The medial segment (S5) is at the anterior and medial aspect of the middle lobe and is defined by B5, A5, and V5.
  • Individual middle lobe segmentectomies are not commonly performed.
• Lower lobe
  • The superior segment (S6) is at the superior posterior aspect of the lobe and is defined by B6, A6, and V6.
  • The basilar segment encompasses the remainder of the inferior aspect of the lobe and has 4 subsegments.
    • The medial basal segment (S7) is at the medial base of the lobe and is defined by B7, A7, and V7.
    • The anterior basal segment (S8) comprises the anterior aspect of the lobe and is defined by B8, A8, and V8.
    • The lateral basal segment (S9) is between the anterior and posterior basal segments at the lateral aspect of the lower lobe and is defined by B9, A9, and V9.
    • The posterior basal segment (S10) comprises the posterior aspect of the lobe and is defined by B10, A10, and V10.
  • Individual basilar subsegmental resections are technically complex and not commonly performed. Removal of the entire basilar segment is more commonly performed.

Left Lung

• Upper lobe
  • The upper segment is divided into the apicoposterior and anterior segments.
    • The apicoposterior segment (S1/S2) forms the superior and posterior aspects of the upper lobe and is defined by B1, B2, A1, A2, V1, and V2.
    • The anterior segment (S3) forms the anterior and inferior aspects of the upper segment down to the lingula and is defined by B3, A3, and V3.
  • The lingular segment, correlating to the right middle lobe, is divided into superior and inferior segments.
    • The superior segment (S4) forms the superior aspect of the lingula and is defined by B4, A4, and V4.
    • The inferior segment (S5) encompasses the remaining inferior aspect of the lingula and is defined by B5, A5, and V5.
  • Left upper lobe segmentectomies are most commonly performed by removing the entire segment, upper segment, or lingular segment, not at the individual subsegmental level.
• Lower lobe
  • The superior segment of the lower lobe (S6) forms the superior aspect of the lobe and is defined by B6, A6, and V6.
  • The basilar segment has 3 subsegments.
    • The anteromedial basal segment (S7/S8) forms the anterior aspect of the lobe and is defined by B7, B8, A7, A8, V7, and V8.
    • The lateral basal segment (S9) forms the lobe between the anteromedial and posterior basal segments and is defined by B9, A9, and V9.
    • The posterior basal segment (S10) forms the posterior aspect of the lobe and is defined by B10, A10, and V10.
  • Left lower lobe segmentectomies are also commonly performed at the larger segment level, superior and basilar segments, rather than at the subsegmental level.[7]

Mediastinal Lymph Node Stations

The mediastinum consists of 14 lymph node stations described and numbered by Mountain and Dresler in 1997. The lymph node stations of the mediastinum are critical for staging and managing lung cancer. They are classified by their anatomical locations, facilitating precise diagnosis and treatment. Here is a detailed description of the mediastinal lymph node stations:

Superior mediastinum

• Station 1: Highest mediastinal nodes
  • Located above the innominate vein and the highest part of the thoracic cavity in the region of the thoracic inlet
• Station 2: Upper paratracheal nodes
  • 2R (right upper paratracheal)
    • Located to the right of the trachea and above the aortic arch but below the upper border of the manubrium
  • 2L (left upper paratracheal)
    • Located to the left of the trachea and above the aortic arch but below the upper border of the manubrium
• Station 3: Prevascular and retrotracheal nodes
  • 3A (prevascular)
    • Located in front of the superior vena cava and the aorta
  • 3P (retrotracheal)
    • Located behind the trachea
• Station 4: Lower paratracheal nodes
  • 4R (right lower paratracheal)
    • Located to the right of the trachea and below the lower border of the aortic arch
  • 4L (left lower paratracheal)
    • Located to the left of the trachea and below the lower border of the aortic arch

Aortic nodes

• Station 5: Subaortic (aortopulmonary window) nodes
  • Located lateral to the ligamentum arteriosum and the aorta and above the left main bronchus
• Station 6: Paraaortic nodes
  • Located around the ascending aorta and aortic arch, but not including the subaortic nodes (station 5)

Inferior mediastinum

• Station 7: Subcarinal nodes
  • Located below the carina of the trachea, between the mainstem bronchi
• Station 8: Paraesophageal nodes (below carina)
  • Located adjacent to the esophagus and below the carina
• Station 9: Pulmonary ligament nodes
  • Located within the pulmonary ligament, which is an extension of the pleura from the hilum to the diaphragm

N1 nodes

• Station 10: Hilar nodes
  • Found in the mainstem bronchi
• Station 11: Interlobar nodes
  • Found at the level of proximal lobar bronchi
• Station 12: Lobar nodes
  • Found at the level of distal lobar bronchi
• Station 13: Segmental nodes
  • Found at the level of segmental bronchi
• Station 14: Subsegmental nodes
  • Found at the level of subsegmental bronchi

N2 nodes

• N2 nodes are located in the mediastinum, outside the lung tissue, but within the central chest area between the lungs.[8] They are further classified based on their specific locations in the mediastinum.
• N2 nodes include stations 2, 4, 5, 6, 7, 8, and 9. 

N3 nodes 

• N3 nodes represent a more advanced stage of lymph node involvement in lung cancer and are located in regions further from the primary tumor compared to N1 and N2 nodes.
• Specifically, N3 nodes are found in contralateral (opposite side) or supraclavicular regions. 

Clinical Significance

• N1 nodes
  • Their involvement usually indicates a more localized spread of lung cancer that may still be considered resectable with curative intent.
• N2 nodes
  • Their involvement indicates more advanced disease with metastasis to the mediastinal lymph nodes; this often requires a combination of therapies, including surgery, chemotherapy, and radiation therapy—and typically signifies a worse prognosis compared to N1 involvement.
• N3 nodes
  • Their involvement generally indicates a poor prognosis and often precludes surgical resection as a treatment option.

Indications

Many diseases can be treated with anatomic segmental resection, including malignant, metastatic, and benign conditions. Examples include:

• Malignant
  • Segmental resection is appropriate in select patients with non–small cell lung cancer, as defined by the National Comprehensive Cancer Network:
    • Poor pulmonary reserve or other contraindications for lobectomy
    • Peripheral nodules with pure adenocarcinoma in situ on histology that:
      • Is less than or equal to 2 cm
      • Has a greater than 50% ground-glass appearance on computed tomography
      • Has a long doubling time confirmed on radiologic surveillance 
  • Segmentectomy should achieve parenchymal margins greater than or equal to 2 cm and sample appropriate N1 and N2 lymph node stations.[9][10][11][12] 

•  Metastatic
  • Resection of pulmonary metastases has been shown to improve survival in colon cancer. The resection may involve resectioning isolated or multiple lesions to minimize loss of pulmonary reserve.[13][14][15]

• Benign
  • Segmentectomy has been documented in treating many conditions, including: 
    • Congenital malformations (bronchial atresia, bronchiectasis, pulmonary arteriovenous malformation, and pulmonary sequestration) [16]
    • Infectious processes (aspergilloma and nontuberculous mycobacterium) 
    • Other pulmonary pathology (bronchiectasis and inflammatory pseudotumors) [17][18]

Contraindications

Segmental sublobar resection is currently not deemed an adequate resection for patients who can tolerate lobectomy. Additionally, it has not been studied in patients with small-cell lung cancer. Other relative contraindications include severe emphysema, interstitial pneumonia, and an extensive adhesive burden due to previous surgeries, as these conditions may render the operation technically unfeasible.[19]    

Equipment

Equipment requirements will depend on the selected surgical approach. All procedures require basic surgical instruments, electrocautery, and closing materials such as sutures, staples, and dressing supplies. Chest tubes with drainage systems should also be available. The specialized equipment needed for each method is listed below.

For an open approach, the following is required:

• Double-lumen endotracheal tube
• Airplane splint for ipsilateral arm extension
• Rib spreader
• Appropriate staplers

For a video-assisted thoracoscopic surgery (VATS) approach, the following is needed:

• Double-lumen endotracheal tube
• Airplane splint for ipsilateral arm extension
• Video system with screens, lighting, and scope
• Appropriate endoscopic instruments [20]

For a robotic approach, the following is needed:

• The requirements of this approach are similar to those of the VATS approach, with the addition of the robotic system and instruments.[21]

Personnel

All cases should be discussed at a multidisciplinary tumor board to determine appropriate multimodality therapy. This board should include oncology, pathology, pulmonology, radiation therapy, and thoracic surgery. Segmental lung resection should be performed by a trained thoracic surgeon specializing in treating lung cancer. In the operating room, the thoracic surgeon will be joined by an assistant surgeon, an anesthesiologist experienced in single-lung ventilation, a scrub nurse familiar with thoracic surgical procedures, and a circulating nurse familiar with thoracic surgery equipment.

Preparation

A significant number of patients will be identified via lung cancer screening programs. These programs are valuable for identifying and monitoring high-risk patients to diagnose lung cancer at a stage amenable to curative therapy. The United States Preventive Services Task Force currently recommends annual screening with low-dose computed tomography (CT) for adults who are between 55 and 80 with a 30-pack-year smoking history who currently smoke or have quit within the past 15 years. There is an ongoing discussion about reducing the smoking history requirement to 20 pack-years and starting the screening at 50.

All patients with suspected or biopsy-proven lung cancer should undergo appropriate staging workup. Standard assessments include CT chest and abdomen with contrast, smoking cessation counseling, pulmonary function testing, bronchoscopy (potentially performed intraoperatively), fluorodeoxyglucose positron emission tomography-CT scan, and consideration of lymph node evaluation. Once the decision to proceed with lung resection has been made, all patients must undergo respiratory testing to determine their ability to tolerate the procedure. Mainstays include pulmonary function testing, ventilation/perfusion scan, and cardiac stress testing.[22]

Technique or Treatment

Open Thoracotomy Approach

The patient is placed in the lateral decubitus position with hyperextension of the chest cavity. The classic approach is the posterolateral thoracotomy. Rib-spreaders are employed to provide visualization of the surgical field. Single-lung ventilation is typically used to facilitate the procedure. The target anatomy is dissected, and resections are performed using appropriate staplers.[23]

VATS Approach

For a typical segmentectomy, such as segment 6 bilaterally, lingulectomy (left S4 and S5), left upper segment (S1, S2, and S3), left basilar segment (S8, S9, and S10), or right basilar segment (S7, S8, S9, and S10), the patient is placed in the lateral decubitus position with hyperextension of the thorax. A 3- to 4-cm incision is made at the fourth or fifth interspace anterior to the latissimus dorsi. The thoracoscope is inserted, and the pleural cavity is inspected. Additional instruments can be inserted through the same incision, and any adhesions should be divided.

For the segmentectomy, the pulmonary artery is identified and followed to the upper segments, which are then divided using a vascular load stapler. The venous supply is determined next. Ensuring venous drainage from the lingula is crucial for the left upper segmentectomy. Finally, the bronchus is identified and stapled off. A leak test is performed to ensure there are no air leaks. The parenchyma is then dissected, and the segment is removed. After lung reexpansion, a thoracostomy drain is typically left in place, and the incision is closed. Atypical segmentectomy, involving individual segmentectomies on the bilateral basilar segments, involves dissection in 3 planes and is more technically challenging. The appropriate surgical approach must be determined via preoperative imaging and should accommodate the individual surgeon's skills.[24]

Robotic-Assisted VATS Approach

Positioning for the robotic-assisted VATS approach is similar to the standard VATS approach, with port placement determined by the targeted segment. There are 2 common approaches, differing in the number of ports used, either 3 or 4.[25][26][27] The robotic system enhances precision and dexterity, allowing for meticulous dissection and resection of lung segments. This approach can offer improved outcomes, including reduced postoperative pain and shorter hospital stays, though it requires specialized training and equipment.

Complications

Early Complications

Early postoperative complications occur within 30 days of surgery. They are typically managed in the hospital setting with close monitoring, additional surgical or medical interventions, and supportive care. They include: 

• Pulmonary edema
• Pneumonia
• Adult respiratory distress syndrome
• Bronchial dehiscence
• Bronchopleural fistula
• Lobar torsion
• Hemothorax
• Chylothorax

Late Complications

Later postoperative complications occur 30 days or more after surgery. They are often managed on an outpatient basis with regular follow-up, additional treatments as needed, and supportive care to improve the patient's quality of life and function. They include: 

• Bronchial stenosis
• Empyema
• Postpneumonectomy syndrome
• Stump thrombus
• Esophagopleural fistula

Significantly, segmentectomy is associated with a higher rate of cancer recurrence and inadequate lymph node sampling, which must be discussed with any patient considering sublobar resection for malignant disease.[28]

Clinical Significance

Lung cancer is the second most common cancer in men and women in the United States and the leading cause of cancer death. Current surgical guidelines for lung cancer recommend lobectomy as the minimum resection for most stages. However, certain patients cannot tolerate that level of lung volume reduction and may undergo segmental lung resection. Additionally, there is ongoing interest and investigation into segmental lung resection as the first-line surgical approach for early-stage non–small cell lung cancer.  

Enhancing Healthcare Team Outcomes

Effective management of segmental lung resection requires a high level of skill, strategic planning, and interprofessional communication among healthcare providers. Surgeons must be adept in minimally invasive techniques, such as VATS and robotic-assisted approaches, to minimize patient recovery time and complications. Anesthesiologists are critical in managing single-lung ventilation and ensuring patient stability throughout the procedure. Advanced clinicians and nurses are essential in perioperative care, providing preoperative education, postoperative monitoring, and managing potential complications. Pharmacists contribute by managing medications, including pain control and antibiotics, to ensure patient safety and optimal recovery. Various therapists, including those in physical therapy, occupational therapy, and respiratory therapy, help to strengthen the patient postoperatively, thereby improving outcomes. 

Coordination and communication among the interprofessional team are crucial for enhancing patient-centered care and outcomes. Regular multidisciplinary meetings, such as tumor boards, enable comprehensive treatment planning and decision-making involving oncologists, radiologists, pulmonologists, and thoracic surgeons. Clear communication ensures that each team member understands their role and the patient's care plan, reducing the risk of errors and improving patient safety. Collaborative care models promote shared decision-making, where patients are informed and involved in their treatment choices, leading to better adherence and satisfaction. Overall, a well-coordinated interprofessional approach optimizes team performance, enhances patient outcomes, and ensures a high standard of care throughout the segmental lung resection process.