Figure 17d. Surgical clip artifact in a 28-year-old man who presented with hypertension. The patient had undergone renal transplantation 3 years earlier. (a, b) Source MR angiogram (a) and MPVR image (b) demonstrate an apparent metallic clip artifact in the distal external iliac artery, just proximal to the transplant artery anastomosis (arrow). (c) Volume-rendered image shows a small corresponding irregularity in the vessel (arrowhead). (d) CO2 angiogram helps confirm that the irregularity was caused by a clip artifact (arrowhead).