Figure 3b. Vascular malformation in a 50-year-old woman. (a) Unenhanced CT scan shows a 1.3-cm-diameter hyperattenuating (42 HU) renal mass (arrow). (b) Contrast-enhanced CT scan obtained during the nephrographic phase reveals enhancement (72 HU) of the mass and shows nearby dilated veins (arrowheads). (c) Contrast-enhanced MR angiogram shows that the mass (arrow) is connected to a draining vein (arrowhead) in the perinephric space.