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CT appearance of the retroaortic anastomoses of the azygos system
1Department of Radiology, Veterans Administration Medical Center, Seattle, WA 98108.
Insights
Retroaortic anastomoses, the terminations of the hemiazygos and accessory hemiazygos veins, can be mistaken for mediastinal lymph nodes on CT scans. Recognizing their continuity with the main veins prevents misdiagnosis.
Area of Science:
- Medical Imaging
- Anatomy
- Thoracic Radiology
Background:
- The posterior mediastinum contains numerous structures that can be challenging to differentiate on computed tomography (CT) scans.
- The hemiazygos vein and accessory hemiazygos vein have unique terminations that can mimic other pathologies.
Purpose of the Study:
- To describe the CT appearance of retroaortic anastomoses.
- To differentiate these venous structures from posterior mediastinal lymph nodes on CT scans.
Main Methods:
- Retrospective review of CT scans from one cadaver and seven patients.
- Analysis of the anatomical course and contrast enhancement patterns of the hemiazygos and accessory hemiazygos veins.
Main Results:
- Retroaortic anastomoses were typically identifiable due to their continuity with the hemiazygos or accessory hemiazygos veins.
- Misinterpretation as lymph nodes can occur with short visible segments or poor contrast opacification.
Conclusions:
- Familiarity with the CT appearance of hemiazygos and accessory hemiazygos vein terminations is crucial.
- This knowledge aids in preventing misdiagnosis of these vascular structures as mediastinal lymph nodes.
Abstract:
The terminations of the hemiazygos and accessory hemiazygos veins can be mistaken for normal or enlarged posterior mediastinal lymph nodes on CT scans of the chest. These terminations are termed the retroaortic anastomoses by anatomists. We studied the CT appearances of these veins on scans of one cadaver and seven patients. We found that the retroaortic anastomoses usually were clearly recognizable because of their continuity with the hemiazygos or accessory hemiazygos vein. However, it is sometimes possible to mistake these vessels for lymph nodes, especially when only short segments of the vessel are visible on a CT image or when the vessel is not clearly opacified by contrast material. Familiarity with the CT appearances of the hemiazygos and azygous veins can prevent their being mistaken for normal or enlarged lymph nodes.