Overview
Definition:
Retrocrural lymph node dissection via a thoracic approach involves the systematic removal of lymph nodes situated in the posterior mediastinum, specifically between the esophagus and the azygos vein, and lateral to the descending aorta
This region is crucial for staging and treating various intrathoracic malignancies, particularly lung and esophageal cancers, as well as metastatic disease
The thoracic approach allows direct access to these nodal stations
This procedure is often performed as part of a larger oncologic resection
It aims to achieve complete nodal clearance for accurate staging and to remove potentially involved lymph nodes to improve local control and survival outcomes
It requires precise anatomical knowledge and surgical skill to avoid vital structures.
Epidemiology:
The incidence of retrocrural lymph node metastasis varies significantly depending on the primary malignancy
For lung cancer, rates of N2/N3 involvement (which can include retrocrural nodes) range from 25-40% depending on the stage
For esophageal cancer, retrocrural nodal involvement is common, often exceeding 50% in advanced stages
Metastatic involvement from other thoracic or even extrathoracic sites can also occur
The prevalence of retrocrural lymph node dissection as a standalone procedure is low
it is usually integrated into resections of primary tumors.
Clinical Significance:
Accurate staging of thoracic malignancies is paramount for determining prognosis and selecting appropriate treatment strategies
Retrocrural lymph nodes are a common site for nodal metastasis from lung and esophageal cancers
Complete dissection of these nodes provides critical pathological information for treatment planning, including the decision for neoadjuvant or adjuvant chemotherapy, chemoradiation, or surgery
Incomplete nodal dissection can lead to understaging, suboptimal treatment, and poorer patient outcomes
Thoracic surgeons perform this dissection to achieve oncologic clearance and potentially improve long-term survival.
Indications
Indications For Dissection:
Primary indication is for staging and therapeutic resection of suspected or confirmed metastatic disease in the retrocrural lymph nodes
This includes lung cancer (clinical N1 or N2 disease, or for precise staging in resectable cases), esophageal cancer (staging and therapeutic resection), and less commonly, thymic malignancies, sarcomas, or metastatic disease from extrathoracic primaries
Diagnostic mediastinoscopy or EBUS-TBNA may precede surgical intervention if imaging is equivocal or to obtain tissue for definitive diagnosis when nodal enlargement is present
The decision is often multidisciplinary, involving oncologists and thoracic surgeons.
Staging Considerations:
Precise staging of mediastinal lymph nodes (N-staging) is essential for the TNM classification of lung and esophageal cancers
The retrocrural nodes constitute specific stations (e.g., Station 7 for subcarinal, Station 8 for paraesophageal, Station 9 for diaphragmatic nodes, which can be accessed from the thoracic approach)
Involvement of these nodes, especially ipsilateral N2 or contralateral N3 disease, significantly impacts treatment
Surgical dissection offers a higher yield of positive nodes compared to less invasive methods in selected cases.
Therapeutic Intent:
Beyond staging, therapeutic resection of involved retrocrural lymph nodes is indicated when they are the dominant site of nodal disease or when they are resectable as part of the primary tumor resection
This is particularly relevant in lung and esophageal cancer where en-bloc resection of the tumor with contiguous nodal tissue is the goal
Complete nodal clearance is associated with improved locoregional control and survival.
Thoracic Approach Techniques
Surgical Access:
The thoracic approach can be achieved through various methods, including standard thoracotomy (posterolateral, lateral, or anterior), video-assisted thoracoscopic surgery (VATS), or robotic-assisted thoracic surgery (RATS)
VATS and RATS are increasingly preferred due to their minimally invasive nature, offering comparable oncologic outcomes with reduced postoperative morbidity, shorter hospital stays, and improved cosmesis
Access to the retrocrural space is typically gained after mobilizing the lung and pleura, and in some cases, by dividing or retracting the inferior pulmonary ligament.
Anatomical Landmarks:
Key anatomical landmarks for identification and dissection include the descending thoracic aorta, the azygos vein (on the right), the hemiazygos vein (on the left), the esophagus, the pericardium, and the diaphragm
The dissection plane is developed between the mediastinal pleura and the prevertebral fascia
Care must be taken to identify and preserve the vagus nerve and the recurrent laryngeal nerve, and to avoid injury to the thoracic duct, phrenic nerve, and intercostal vessels.
Dissection Methodology:
Dissection begins by identifying the boundaries of the lymph node package
Using electrocautery or harmonic scalpel, nodes are meticulously dissected away from surrounding structures
The dissection progresses superiorly towards the subclavian artery origin and inferiorly towards the diaphragm
On the right side, the azygos vein is often encountered and may need to be ligated and divided for complete access
On the left, the descending aorta and thoracic duct are critical structures to avoid
Nodes are removed in anatomical blocks corresponding to specific mediastinal stations
Specimen orientation is crucial for pathology
Each nodal station should ideally be addressed and removed completely if indicated by the primary tumor location and imaging findings.
En Bloc Resection:
In cases of primary lung or esophageal cancer, retrocrural lymph node dissection is typically performed as part of an en-bloc resection
For lung cancer, this may involve lobectomy or pneumonectomy with mediastinal lymphadenectomy
For esophageal cancer, it is part of esophagectomy where mediastinal and abdominal lymphadenectomy are performed
The goal is to remove the primary tumor and all contiguous involved nodal tissue in a single specimen to maximize oncologic clearance and reduce the risk of positive margins or skip metastases.
Preoperative Preparation
Patient Evaluation:
Comprehensive evaluation includes detailed history, physical examination, pulmonary function tests (PFTs), cardiac assessment, and nutritional status evaluation
Risk assessment for major thoracic surgery is crucial
Smoking cessation advice and preoperative respiratory physiotherapy are recommended for smokers
Baseline laboratory investigations (CBC, electrolytes, renal and liver function tests, coagulation profile) are mandatory.
Imaging And Staging:
Preoperative imaging is essential for defining the extent of disease and nodal involvement
This typically includes contrast-enhanced CT scan of the thorax and upper abdomen, and often PET-CT scan for staging and assessing metabolic activity of nodes
Endobronchial ultrasound (EBUS) or endoscopic ultrasound (EUS) with fine-needle aspiration (FNA) are often used for biopsy-proven nodal staging, especially for suspicious nodes detected on CT/PET
Bronchoscopy and esophagoscopy are also performed to evaluate the airway and esophagus.
Informed Consent:
Detailed discussion with the patient regarding the risks, benefits, and alternatives to surgery, including the potential for complications such as bleeding, infection, air leak, phrenic nerve injury, recurrent laryngeal nerve injury, chylothorax, persistent pain, and the possibility of incomplete resection or need for further treatment
The rationale for the thoracic approach and the extent of lymph node dissection will be explained
The use of minimally invasive techniques (VATS/RATS) will also be discussed.
Postoperative Care
Monitoring:
Close monitoring in the postoperative period is essential
This includes vital signs, oxygen saturation, respiratory status (breath sounds, chest tube drainage), fluid balance, and pain control
Cardiac rhythm monitoring may be necessary
Neurological assessment for any signs of nerve injury is important.
Pain Management:
Effective pain management is crucial for early mobilization and respiratory physiotherapy
This can involve patient-controlled analgesia (PCA) with opioids, epidural analgesia, or intercostal nerve blocks
Non-opioid analgesics and adjuvant medications are also used.
Chest Tube Management:
Chest tubes are typically placed to drain the pleural space and may be connected to suction
Management involves monitoring drainage volume and character, and ensuring proper tube function
Early removal of chest tubes is encouraged once drainage is minimal and lung expansion is satisfactory
Mobilization and physiotherapy are key to preventing complications like atelectasis and pneumonia.
Nutritional Support:
Adequate nutrition is vital for wound healing and recovery
For patients undergoing esophagectomy, enteral feeding via a nasojejunal tube or parenteral nutrition may be required
Patients who have undergone lung resection require adequate caloric and protein intake to support respiratory muscle strength and recovery
Early oral feeding is encouraged as tolerated.
Complications
Early Complications:
Bleeding, infection (pleural empyema, wound infection), air leak, pneumothorax, atelectasis, pneumonia, prolonged air leak, chylothorax (injury to thoracic duct), phrenic nerve injury (leading to diaphragmatic dysfunction), recurrent laryngeal nerve injury (vocal cord paresis/paralysis), cardiovascular events, blood loss requiring transfusion.
Late Complications:
Chronic pleural effusion, bronchopleural fistula, incisional hernia, chronic pain (post-thoracotomy pain syndrome), lymphedema (rare with thoracic dissection unless extensive), recurrent disease, diaphragmatic paralysis, vocal cord paralysis causing dysphagia or dyspnea.
Prevention Strategies:
Meticulous surgical technique, careful dissection to avoid injury to vital structures, appropriate use of electrocautery, adequate chest tube drainage, early mobilization, aggressive pulmonary physiotherapy, meticulous chest tube removal criteria, and judicious use of prophylactic antibiotics where indicated
Careful patient selection and optimization preoperatively can mitigate risks
Intraoperative nerve monitoring can help identify and protect recurrent laryngeal and phrenic nerves.
Prognosis
Factors Affecting Prognosis:
Prognosis is primarily determined by the stage of the primary malignancy, the extent of nodal involvement (number and location of positive nodes, ipsilateral vs
contralateral), the success of complete oncologic resection (negative margins), the presence of distant metastases, and the patient's overall health status
The type of primary cancer also influences prognosis.
Outcomes With Treatment:
For early-stage lung and esophageal cancers treated with curative intent including complete mediastinal lymphadenectomy, survival rates can be significantly improved
For example, Stage I lung cancer treated with lobectomy and mediastinal dissection has a good prognosis
Advanced stage disease with extensive retrocrural nodal involvement generally has a poorer prognosis, often requiring multimodal therapy
Patients undergoing resection for metastatic disease without distant spread may have improved survival compared to unresectable cases.
Follow Up:
Long-term follow-up is crucial for surveillance of recurrence, monitoring for treatment-related side effects, and assessing quality of life
This typically involves regular clinical examinations, chest imaging (CT scans), and potentially PET-CT scans at defined intervals
Surveillance protocols vary based on the primary cancer and stage
Adjuvant therapy decisions post-operatively are guided by the pathology report from the dissected lymph nodes.
Key Points
Exam Focus:
Retrocrural nodes are key for staging lung and esophageal cancers (mediastinal stations)
Thoracic approach (VATS/RATS preferred) allows access
Avoid thoracic duct, vagus, recurrent laryngeal, phrenic nerves
En-bloc resection with primary tumor is oncologically sound
Complications include chylothorax, nerve injuries, pleural collections
Precise pathological staging is crucial for treatment planning.
Clinical Pearls:
In VATS/RATS, identify aorta, esophagus, and azygos/hemiazygos veins early
The plane of dissection is critical – stay superficial to the prevertebral fascia
Consider the origin of the tumor to determine the extent of dissection
For left-sided lesions, the thoracic duct is a critical structure posterior to the esophagus
Thorough mediastinal nodal sampling improves staging accuracy and patient management decisions.
Common Mistakes:
Inadequate dissection leading to understaging of nodal disease
Injury to the thoracic duct causing chylothorax, or recurrent laryngeal/phrenic nerves causing significant morbidity
Failure to recognize and address bulky or fixed lymph nodes preoperatively
Incomplete resection of nodal stations during en-bloc procedures
Not properly orienting specimens for pathology, leading to ambiguous staging reports.