The large left sided aortic aneurysm sac (red dotted line) is mostly filled with thrombus ( * ). At the superior margin, contrast (blue arrows) can be seen passing between the thrombus and the wall of the aneurysm. Extensive retroperitoneal hyperdense fluid is present, consistent with blood (green).
The left kidney (yellow dotted line) is hydronephrotic, and this combined with direct compression and compression of the renal vessels by the aneurysm demonstrates less contrast enhancement than the right kidney.