Figure 13d. UPJO in a 54-year-old man. (a) Coronal MPR image shows mild right hydronephrosis with a transition point in the region of the ureteropelvic junction (arrow). (b) Coronal volume-rendered view shows right UPJO. The dilated renal pelvis is noted to balloon anteriorly (black arrow) over a second lower-pole segmental vein draining directly to the inferior vena cava (white arrowhead). Black arrowhead = main renal vein, white arrow = distal ureter beyond the UPJO. (c) Coronal MIP image shows the right UPJO. The main renal artery (short arrow) and a variant lower-pole segmental artery (long arrow) are noted. (d) Oblique sagittal MPR image shows that the enlarged extrarenal pelvis balloons posteriorly over the lower-pole artery and vein (short arrow). Note that the vessels are above the transition zone of the UPJO (long arrow).