showing another case seen during this summer. Preoperative chest radiography for knee surgery in a 57-year-old man. More images will be shown on Wednesday.
What do you see?
New images are shown:
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Findings: PA radiographs shows a right mediastinal mass at the level of the tracheal bifurcation (A, arrow), which has not changed significantly in comparison with a chest film taken for pneumonia one year earlier (B, arrow).
Several of you have mentioned a triangular shadow at the right cardiophrenic angle
(A-B, red arrows). This appearance should suggest paracardial fat pad as the first choice.
The differential diagnosis of a right mediastinal mass at the level of the tracheal bifurcation is simple: most of the times it is either an enlarged azygos vein or lymphadenopathy.
CT shows a dilated azygos vein with a prominent azygos arch (C-D, arrows), suggesting a impeded blood flood either in the inferior or superior vena cava. Considering that the patient is asymptomatic, the most likely diagnosis is congenital interruption of the inferior vena cava, with azygos continuation. The diagnosis is confirmed noting the absence of the suprarenal portion of the IVC (C, circle) and the association of other congenital anomalies, such as polisplenia (C, red arrows) and abnormal bifurcation of the bronchial tree (E, arrows).
Coronal CT confirms that the triangular paracardial shadow represents paracardiac fat.
Final diagnosis: Congenital absence of IVC with azygos continuation
Congratulations to MK, who made a late (and accurate) diagnosis of prominent azygos vein
Teaching point: remember that the most common right lower paratracheal masses are either an enlarged azygos vein or mediastinal lymph nodes.