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Superior diaphragmatic lymph nodes

The superior diaphragmatic lymph nodes are a group of small lymph nodes located on the thoracic surface of the diaphragm, near its attachment to the sternum, costal margins, and vertebral column. They are situated along the upper surface of the diaphragm, adjacent to the pericardium, pleura, and lower mediastinal structures.

These lymph nodes form part of the mediastinal and diaphragmatic lymphatic network, acting as important junctional nodes between abdominal and thoracic drainage systems. They collect lymph from the diaphragm, lower thoracic wall, pericardium, pleura, and portions of the liver and upper abdominal viscera.

They communicate with the posterior mediastinal nodes, parasternal nodes, and inferior diaphragmatic (phrenic) nodes, creating pathways for the spread of thoracic and upper abdominal malignancies and infections. Their location and drainage role make them important in oncology staging (lung cancer, esophageal carcinoma, gastric carcinoma, and hepatic tumors) as well as in inflammatory and infectious diseases.

Synonyms

  • Thoracic diaphragmatic lymph nodes

  • Peridiaphragmatic lymph nodes (superior group)

Function

  • Drain lymph from the thoracic surface of the diaphragm, pericardium, and pleura

  • Contribute to lymphatic outflow from liver (superior surface), esophagus, and anterior abdominal wall

  • Connect abdominal and thoracic lymphatic systems, enabling metastatic spread across compartments

  • Serve as sentinel nodes in staging of thoracic and abdominal malignancies

MRI Appearance

T1-weighted images:

  • Normal nodes: intermediate-to-low signal intensity relative to muscle

  • Enlarged or pathological nodes may alter to heterogeneous signal

T2-weighted images:

  • Normal nodes: intermediate signal

  • Reactive or malignant nodes may appear hyperintense

STIR:

  • Normal nodes appear as  intermediate signal against suppressed fat background

  • Enlarged nodes or nodes with edema/infiltration appear bright hyperintense

T1 Fat-Saturated (Pre-contrast):

  • Nodes appear intermediate signal, distinguishable from suppressed fat planes of mediastinum and diaphragm

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Normal nodes: mild homogeneous enhancement

  • Malignant nodes: heterogeneous or intense enhancement

  • Helps distinguish reactive vs metastatic involvement

MRI Non-Contrast 3D Imaging:

  • Provides a 3D anatomical map of lymph nodes relative to diaphragm, heart, and mediastinum

  • Useful in oncology staging and surgical planning

CT Appearance

CT Pre-Contrast:

  • Nodes appear as soft tissue densities on the diaphragmatic surface

  • Small nodes may be difficult to separate from adjacent fat planes

CT Post-Contrast:

  • Normal nodes enhance mildly and homogeneously

  • Malignant or reactive nodes may show enlargement, heterogeneous enhancement, necrosis, or calcification

  • Helps detect subtle nodal enlargement in lung, esophageal, hepatic, and gastric cancer staging

CTV (CT Venography):

  • Enhances visualization of nodal groups in relation to venous and mediastinal structures

  • 3D reconstructions map thoracoabdominal lymphatic pathways

  • Valuable in oncology staging and interventional planning

Clinical Importance

  • Frequently involved in lung cancer, esophageal carcinoma, gastric carcinoma, and liver tumors

  • Can harbor metastases from breast, mediastinal, and abdominal malignancies

  • Involved in infectious diseases such as tuberculosis or fungal infections

  • Important landmarks for thoracic surgery and radiation therapy planning

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Superior diaphragmatic lymph nodes