Dr. Pepe’s Diploma Casebook: CASE 136 – SOLVED

Findings: The sharp outer border of the opacity suggests a mediastinal mass. The indistinct upper contour (A, arrow) places it in the anterior upper mediastinum. The diagnosis is suggested by a negative finding: the trachea is not pushed towards the left as it should be if the opacity were a goiter or mediastinal mass. Therefore, the most likely diagnosis is a tortuous innominate artery. Enhanced axial CT confirmed this diagnosis (B, arrow).

Findings: The PA radiograph shows a triangular opacity in the upper left hemithorax that simulates LUL collapse. Again, the diagnosis is based in a negative finding: there is no elevation of the left hilum (A, white arrow), which should accompany collapse. In addition, the trachea is slightly displaced to the right (A, red arrow), suggesting a mediastinal mass. The lateral view (B) is unremarkable.

Findings: the lateral film shows a bulging ascending aorta (B, white arrow). A line has been traced to measure an apparent dilatation of the ascending aorta (B, yellow arrow). The correct diagnosis is based on a negative finding: the ascending aorta should be enlarged in the PA radiograph as well, and it is not (A, asterisk). Therefore, the chest is normal.

The obvious error is that the line is drawn from the anterior aspect of the aorta, outlined by lung air, to an imaginary point in the mediastinum, which may or may not be the posterior aortic wall. Remember that the posterior wall of the aorta is in contact with the mediastinal tissues and, according to the silhouette sign, cannot be visible. Therefore, whoever traced the line was wrong.
MRI confirmed a normal aorta and that no other abnormalities were present. The moderate bulging of the ascending aorta in the lateral film is due to a combination of a moderate pectus excavatum and a narrow AP diameter of the chest (see case below).

Normal chest with an appearance similar to that of the previous case in a 59-year-old asymptomatic man. The narrow AP diameter of the chest accounts for the prominent ascending aorta in the lateral view (B, arrow). The PA radiograph does not show dilatation of the ascending aorta (A, asterisk), confirming the absence of pathology.

Findings: the PA chest radiograph shows four main findings, three of them positive and one negative. The rounded shadow at the aortic knob (A, white arrow) is a typical aortic nipple, secondary to an enlarged left superior intercostal vein (LSIV, red arrow), which joins the brachiocephalic vein superiorly and the hemiazygos vein inferiorly (yellow arrow), giving a double contour to the para-aortic line.
The large aortic nipple indicates increased blood flow in the azygos-hemiazygos system.
The negative finding is that the azygos vein should be enlarged too. However, it is not, suggesting the diagnosis of congenital absence of the azygos vein. Axial enhanced CT confirms the missing azygos vein (B, circle) and the large hemiazygos (B, arrow).

A serendipitous discovery in this case is that the SVC is also absent. Axial CT (C) confirms the lack of SVC (neither right nor left) and the enlarged LSIV (C, arrow). CT reconstructions show the hemiazygos vein (E, red arrows) running parallel to the aorta (A) and draining blood from the innominate veins (D, yellow arrows), which join the LSIV (D, black arrow). Absent SVC is associated with cardiac arrhythmias.