Lymphocele of the thoracic duct

• Non-enhancing tubular or multi-cystic dilated structure along the midline coursing from the abdomen to mediastinum
• Characteristic location posterior to the esophagus extending from renal hila level caudally to left subclavian-internal jugular vein junction cranially
• Water density attenuation slightly lower than arterial and venous structures with multi-compartmental appearance

• Thoracic duct lymphoceles appear as non-enhancing dilated structures with water density attenuation and tubular or multi-cystic morphology following the natural course of the thoracic duct.
• The lesion typically begins at the level of the renal hila in the abdomen (right of the first and second lumbar vertebrae, immediately adjacent to the abdominal aorta) and extends cranially through the mediastinum.
• The structure demonstrates multi-compartmental appearance with areas of more focal dilatation creating cyst-like formations, rather than uniform dilatation.
• Attenuation is characteristically slightly lower than arteries and veins, helping distinguish it from vascular structures.
• Absence of enhancement on contrast-enhanced CT helps confirm lymphatic origin rather than fluid collections from other sources.
• The terminal portion of the thoracic duct descends anterior to the first part of the subclavian artery and terminates at the junction of the left subclavian vein and internal jugular vein.
• The thoracic duct courses along the right side of the aorta in the abdomen and chest before crossing to the left side in the upper mediastinum.
• The lesion represents lymph-filled dilatation of the normal thoracic duct, not a pathological process requiring intervention.

• Lymphadenopathy: Unlike lymphoceles, lymph nodes are discrete rounded structures with measurable short-axis dimensions and may demonstrate rim enhancement.
• Esophageal diverticulum or duplication cyst: Can mimic thoracic duct cysts but typically occurs in the mid-esophagus and may show communication with esophageal lumen.
• Mediastinal mass (thymoma, teratoma): Located anterior in mediastinum rather than posterior and typically demonstrates heterogeneous enhancement.
• Pancreatic cyst or pseudocyst: Located in the left upper quadrant abdomen and does not extend into the mediastinum along the expected thoracic duct course.
• Aortic aneurysm: Shows arterial enhancement and lacks the characteristic tubular lymphatic morphology.
• Venous anomaly or duplication: Demonstrates venous enhancement on contrast-enhanced imaging and different anatomic distribution.

Describe the finding as a non-enhancing, water-density, tubular or multi-cystic dilatation of the thoracic duct coursing from the abdomen to the left subclavian-internal jugular junction, and explicitly state this is a benign incidental finding consistent with thoracic duct lymphocele without features suggesting pathology.

• Mistaking the thoracic duct lymphocele for a true pathological cyst or mass lesion, leading to unnecessary further investigation or intervention.
• Confusing the dilated thoracic duct with lymphadenopathy, particularly in the retrocrural region, resulting in erroneous lymph node staging.
• Failing to recognize the characteristic non-enhancing nature on contrast-enhanced imaging, which distinguishes it from vascular structures or neoplasms.
• Not appreciating the normal anatomic variation and course of the thoracic duct, leading to misidentification of the structure itself as abnormal.