Fig. 6.

Seventeen-year-old with left hydronephrosis and cyclic vomiting who has previously undergone left pyeloplasty. a Maximum intensity projection (MIP) reconstruction of 3D T2-weighted fast spin-echo image showing abrupt narrowing of the left renal pelvis at the level of the ureteropelvic junction (arrow). b MIP reconstruction of a post-contrast excretory image shows symmetric renal enhancement and excretion of contrast. Contrast readily flows past the narrowed, yet patent UPJ (blue arrow) as evidenced by the presence of contrast within both distal ureters (red arrows). On dynamic imaging, there was symmetric passage of contrast material through the kidneys and into the renal collecting systems and ureters suggesting no clinically relevant obstruction. c Example of region of interest overlying the left kidney performed during segmentation. d Time-vs.-signal intensity curves from the kidneys and abdominal aorta are obtained from dynamic post-contrast MR urograms post-processing; in this case, the curves demonstrate symmetric renal uptake and excretion confirming lack of obstruction in the left kidney