Clinical History:
This 71-year-old man presented to the emergency room with a fever up to 39°C and a general decline in his state of health. Two weeks previously, he underwent a partial resection of the right kidney due to suspected renal cell carcinoma, that turned out to be an hemorrhagic cyst.
Diagnosis:
Perinephric abscess and false aneurysm of a right renal artery branch.
MR Technique:
The exam was acquired on a 32-channel 3 T scanner (Siemens MAGNETOM Tim Trio) using one body matrix coil and two clusters of the inbuilt spine coil. The 3D FLASH MRA (fast low angle shot, TR/TE 3.03/1.05 msec, voxel size 0.9×1.0x1.2mm³, acquisition time 18 sec, parallel imaging GRAPPA factor 3, Cartesian k-space sampling) was acquired after the injection of 0.07 mmol/kg of a 0.5 M gadolinium-chelate formulation at 1.5 ml/sec followed by a 30 ml saline chaser at the same flow rate. To guarantee optimal filling of k-space, a test bolus was performed using 1 ml of 0.5 M gadolinium chelate. After the arterial and venous phase of the MRA, a volume-interpolated breath hold exam (VIBE) sequence (TR/TE 3.45/1.23ms, voxel size 1.2×1.3×3.0mm³, parallel imaging GRAPPA factor 2, acquisition time 20 sec) was acquired in the coronal orientation.
Imaging Findings:
In the coronal MIP-view of the high-resolution MR angiogram (A) an irregularly shaped strongly enhancing mass directly extending from the renal artery can be appreciated. This false aneurysm reveals isointense enhancement compared to the renal arteries during the arterial and venous (not shown) phase of the high-resolution MR angiogram. In the coronal VIBE image (B), a perinephric abscess can be visualized communicating with the subhepatic space. On this image, after contrast media application, decreased signal intensity of the right kidney parenchyma can be observed in comparison to the left kidney as a consequence of the operation and the inflammatory reaction of the kidney.
