Magnetic resonance imaging and pathological evaluation of a case of false aneurysm of descending aorta with rupture into the left lung

Imaging diagnosis of a false aneurysm of descending aorta which is very rare in a 79-year old male is studied in comparison with the findings of the postmortem examination. The patient died of rupture into the left lung. A chest roentgenogram showed a tumor shadow in the left upper mediastinum with inflammatory densities in the left upper lobe. The tomogram revealed that there was complete obstruction of apical bronchus of the left lung. The bolus CT showed a true aneurysm at the beginning of descending aorta. MRI was performed using a 0.15-Tesla resistive magnent. Ungated spin-echo and inversion recovery images of the thoracic aorta were obtained in the transaxial and sagittal planes. The spin-echo images revealed the location of the aneurysmal lumen, and the IR images showed thrombosis on the aneurysmal wall. Therefore, the clinical diagnosis was an aortic aneurysm of the descending aorta with rupture into the lung. Pathological diagnosis by autopsy was a false aneurysm. There was a saccular pseudoaneurysm with old thrombus and a circular entrance at the beginning of the descending aorta, just below the atheroma plaque with calcification, occupying the subpleural region near the apex of the S1+2 of the left lung. Histologically this case was identified a rupture of a false aneurysm with marked scars on some parts of its wall caused by old pleuritis, anastomosing the peripheral bronchus of B1+2. There was massive hemorrhage throughout both lungs. Although it is very difficult to distinguish a false aneurysm from an aortic true aneurysm, MRI has great advantage of providing valuable information about blood flow and thrombosis, comparing with CT. (author)