• Lymphatic system including ducts and nodes are distributed throughout the thoracic cavity, including around the lungs, bronchi, and along the major blood vessels.
• Pulmonary lymphatic vessels may thus be classified into
  •  Drains along the veins
  • Superficial system
    •  pleural
    • interlobular (in interlobular septa) and ,
      • drains centrally along the veins to the hilum
    • intralobular
      • some of the drainage of the interstitium of the secondary lobule
  • Deeper System
    •  intralobular.
      • around
        • bronchovascular bundle
        • perivascular (associated with a blood vessel),
        • peribronchiolar ( least prominent),
        • interalveolar (in interalveolar septa)
      • drains centrally along the bronchovascular bundle
      • join the broncho-mediastinal trunks
  • Lymph node enlargement can result from various diseases, categorized by their underlying etiology. The causes can be grouped into the following TCV disease categories:
    1. Infection:
       • Tuberculosis (TB): A common cause of mediastinal lymphadenopathy, particularly in endemic areas. TB causes granulomatous inflammation of lymph nodes.
       • Bacterial infections: Conditions like bacterial pneumonia, bronchitis, or infections like cat-scratch disease (Bartonella) and brucellosis can cause reactive lymphadenopathy.
       • Viral infections:
         • Epstein-Barr virus (EBV): Causes infectious mononucleosis, which can lead to generalized lymphadenopathy.
         • HIV/AIDS: Can cause generalized lymphadenopathy, especially during acute infection or advanced stages of the disease.
         • Cytomegalovirus (CMV): Another viral infection causing lymph node enlargement.
       • Fungal infections: Histoplasmosis and coccidioidomycosis can cause enlarged lymph nodes, particularly in endemic areas.
    2. Inflammation:
       • Sarcoidosis: A systemic granulomatous disease that often causes bilateral hilar lymphadenopathy. It involves non-caseating granulomas and affects multiple organs.
       • Rheumatoid arthritis (RA): Can cause reactive lymphadenopathy as part of a systemic inflammatory response.
       • Systemic lupus erythematosus (SLE): This autoimmune disease can cause generalized lymphadenopathy due to inflammation.
    3. Neoplasm:
       • Lung cancer (primary and metastatic): Lymph node enlargement in the mediastinum or hilar regions is common, often as a result of metastatic disease. Non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) can both spread to lymph nodes.
       • Lymphoma: Includes Hodgkin’s lymphoma and non-Hodgkin lymphoma. These cancers often present with large, painless lymph nodes in the chest or supraclavicular regions.
       • Metastatic cancer: Tumors from the breast, head and neck, esophagus, or other organs can spread to nearby lymph nodes, causing enlargement.
    4. Mechanical Causes:
       • Obstruction: Compression or blockage of lymphatic drainage can result in localized lymph node enlargement. This can occur due to tumors or lymphatic vessel blockage.
       • Chylothorax: Lymphatic fluid leakage into the pleural cavity can result in enlarged lymph nodes due to the accumulation of lymphatic fluid.
    5. Trauma:
       • Post-surgical lymphadenopathy: After thoracic or chest surgery (e.g., lung biopsy, lymph node dissection), reactive enlargement of lymph nodes may occur as part of the healing process.
       • Trauma: Injury to the chest or lymphatic vessels can result in localized swelling or inflammation of nearby lymph nodes.
    6. Metabolic:
       • Gaucher’s disease: A lysosomal storage disorder that can cause enlargement of the spleen, liver, and lymph nodes due to accumulation of glucocerebrosides.
       • Amyloidosis: The deposition of amyloid proteins in tissues, including lymph nodes, can lead to their enlargement.
    7. Circulatory:
       • Congestive Heart Failure (CHF): Fluid congestion in the chest can cause reactive enlargement of lymph nodes due to lymphatic drainage impairment.
       • Pulmonary edema: As a result of circulatory issues like left heart failure, edema may result in secondary lymph node enlargement due to lymphatic overload.
    8. Immune:
       • HIV/AIDS: Can cause generalized lymphadenopathy, particularly in the early stages or advanced stages of the disease, due to immune system activation.
       • Autoimmune diseases: Conditions like SLE, Sjogren’s syndrome, or vasculitis may lead to reactive lymph node enlargement due to immune system dysregulation.
    9. Inherited and Congenital:
       • Primary immunodeficiencies: Such as Wiskott-Aldrich syndrome or hyper-IgM syndrome, may lead to persistent or recurrent infections, causing chronic lymph node enlargement.
       • Lymphatic malformations: Congenital abnormalities in lymphatic development can result in abnormal lymph node enlargement and lymphatic drainage issues.
    10. Idiopathic:
        • Idiopathic granulomatous disease: Some conditions, like Wegener’s granulomatosis or Churg-Strauss syndrome, may cause unexplained lymph node enlargement.
    11. Iatrogenic:
        • Post-radiation lymphadenopathy: Lymph node enlargement may occur after radiation therapy for cancers such as lung cancer or lymphoma.
        • Post-treatment lymphadenopathy: Medications, such as some antibiotics or antiepileptics, may cause lymphadenopathy as an adverse reaction.
    12. Functional:
        • Reactive lymphadenopathy: A transient enlargement of lymph nodes due to functional responses from the immune system, often following mild infections or inflammatory processes.
    13. Psychological and Psychiatric:
        • Psychological or psychiatric conditions do not typically directly cause lymph node enlargement. However, stress and chronic psychological conditions can affect immune function, possibly leading to secondary responses such as mild lymph node enlargement.

    Next Step:

    • Imaging evaluation:
      • For suspected lymph node enlargement, CT or MRI of the chest is usually the next step to assess the size, location, and number of enlarged nodes, and to determine if there is associated disease (e.g., malignancy, infection).
      • Biopsy: If the cause is unclear, a biopsy of the enlarged lymph node may be necessary for definitive diagnosis, especially in suspected malignancy or infections.

 The final common pathway for all the lymphatic is via the thoracic duct which enters the left subclavian vein.

Cisterna Chyli

The Superficial and Deep Lymphatic Systems at the Secondary Lobular Level

 

 

• Categories

• Pulmonary Lymph Nodes: Found within the lung tissue and around the bronchi, they drain lymph from the lung parenchyma and airways.
• Hilar Lymph Nodes: Located at the hilum of each lung, these nodes receive lymph from the lung tissue and airways.
• Mediastinal Lymph Nodes: Located in the mediastinum (between the lungs), these nodes are involved in draining lymph from the lung hilum, the esophagus, the heart, and the trachea.
• Cervical Lymph Nodes: These are located in the neck and receive lymphatic drainage from the superior portion of the lungs, particularly from the upper lobe and trachea.
• Supraclavicular Lymph Nodes: Located just above the clavicle, these nodes can be involved in the spread of lung cancer or infections.
• Paratracheal Lymph Nodes: These nodes are located beside the trachea and drain lymph from the trachea, bronchi, and lungs.

Difference Between the Upper Lobes and Lower Lobes

• The lymphatic drainage of the upper lobes and lower lobes of the lungs differs
  • In the upper lobes
    • lymphatic drainage is more extensive and interconnected
    • because the
      • upper lobes contain a
        • larger number of lymph nodes
        • lymphatic vessels in the upper lobes also tend to be
          • larger and
          • more numerous and therefore
            • more efficient circulation of lymphatic fluid.
        • the lower lobes of the lungs
          • limited lymphatic drainage system,
          • fewer lymph nodes and
          • smaller lymphatic vessels.

Lymph Nodes on the Fissures

Halo Sign Around a Malignant Mass and
Lymphangitis Carcinomatosis

Lymph Nodes

 

Most of the visible lymph nodes are within the hila and mediastinum.  However there are  lymph nodes that lie close to the periphery of the lung. These are relatively small measuring  approximately 2mm. in diameter.  They become larger towards the hila, reaching diameters of between 5 to 10mm.

 

The mediastinal nodes have been divided into 4 main groups;  the superior mediastinal, aortic, inferior mediastinal, and N node are the designated groups.  Within these groups there are 14 nodal stations.  These 14 stations have been given both names and numbers to aid in the classification and staging of disease.

 

Group 3 called “prevascular and retrotracheal nodes” can only be appreciated on the axial images since they are found relatively anterior and posteriorly in the chest.

 

Superior Mediastinal Nodes

 

1 Highest Mediastinal Nodes

2 Upper Tracheal Nodes

3 Prevascular and Retrotracheal Nodes

4 Lower Paratracheal Nodes

Aortic Nodes

 

5 Subaortic Nodes (A-P window)

6 Paraaortic Nodes (Ascending Aorta or Phrenic)

Inferior Mediastinal Nodes

 

7 Subcarinal Nodes

8 Paraesophageal Nodes

9 Pulmonary Ligament Nodes

10 Hilar Nodes

11 Interlobar Nodes

12 Lobar Nodes

13 Segmental Nodes

14 Subsegmental Nodes

 

A Patient with Sarcoidosis with Calcified Nodes at Many Stations

50-year-old male presents with history of Stage 4 sarcoidosis acute chest pain and dyspnea
The initial CXR shows a left sided pneumothorax, diffuse nodular pattern with confluent perihilar infiltrates and a left pleural effusion
A chest tube was placed and a chest CT showed confluent fibrotic masses in the hilar regions totally surrounding the bronchovascular bundles with encasement of the middle lobe artery. In addition, multiple lympho-vascular micronodules are demonstrated. The pulmonary artery measures 32.7mm indicating pulmonary hypertension.
A CXR during this admission shows re-expansion of the pneumothorax. Left lung volume is reduced.
The patient presents 2 years later, again with progressive dyspnea and chest pain and CT PA shows encasement of the airways, right middle lobe pulmonary artery and left lower pulmonary vein by the fibrotic broncho vascular masses, and non-occlusive, subacute pulmonary embolus of the LPA. There are moderate bilateral pleural effusions, calcified lymph nodes, with ongoing pulmonary hypertension with right ventricular enlargement, right atrial enlargement, tricuspid regurgitation and pulmonary hypertension. At this time the patient is intubated.
He again presents 1 month after with chest pain and dyspnea. At this time, he has a tracheostomy. The scout frontal view shows persistent encasement of the left upper lobe bronchus and significant reduction on the volume of the left lung with elevated left hemidiaphragm.
CT PA has similar findings with a large right pleural effusion and unresolved large non occlusive thrombus in the left pulmonary artery.

See Radiographics

Applied Anatomy

Knowledge of the anatomy of the secondary lobule is key to the understanding of the subpleural lymphatic system since the lymphatic of this region run in the interlobular septa.  The anatomy of the secondary lobule was extensively discussed in part 1 of the lung module.  The ability to image the secondary lobule is key to the diagnosis of many of the interstitial lung diseases and it requires high resolution imaging to enable distinction between changes in the interlobular septa changes within the central bronchovascular bundle and changes within the lobule itself.  Since the subpleural lymphatics run in the interlobular septa, it becomes our focus when lymphatic disease is evaluated.

 Certain diseases have a predilection for the lymphatic system at the subpleural level including sarcoidosis.  On the other hand diseases such as lung carcinoma have a predilection for the deep and central nodal system.  Since the systems do connect and are both usually involved i is imperative to evaluate both systems.

 

 

 

Subpleural System

 

 The polygonal shape of the secondary lobule is a key shape to recognise.  These lobules are well formed at the lung apices, lung bases and particularly at the periphery of the lung.  The septa are not usually appreciated in healthy lungs, but may be seen in only mildly diseased lungs as well as advanced disease in the lung.  Their presence does not necessarily indicate lymphatic disease since the connective tissue of the septa, and the venules are also located within them.

The Deep System

The subpleural and deep system have a final common pathway.  The image below shows this connection by demonstrating spread of malignant disease in the interlobular septa, around the bronchi and in an intrapulmonary lymph node.

Mediastinal Nodes

 

 

Size of Nodes

  In general , although we often measure the size, and specifically the short axis of the nodes to determine the presence of disease, we understand that this is a fairly inaccurate method with low specificity .  A short axis of more than 10mm implies a pathologically involved node.  Often the large node may be reactive and may not contain malignant disease.  PET scanning has been an important advance to aid in the distinction between reactive and malignant lymphadenopathy.

Large Reactive Node – Pathology negative
The node in the azygos region is pathologically enlarged but at pathology was shown to be reactive.  note the subtle deformity of the azygos region on the CXR
33082c02 Courtesy Ashley Davidoff MD TheCommonVein.net

 

Lymphoma

 

Small cell Lung Carcinoma

Elevated Right Main Stem Bronchus and Encasement

Bilateral Lymphangitis Carcinomatosis in a Patient with Adenocarcinoma

 

Lymphoma with Giant Rim Enhancing Lymph Nodes

References and Links

Cases

044Lu Chronic Inactive TB  Lymphatic Distribution
95Lu Sarcoidosis Lymph Nodes with Egg Shell Calcification