Figure 8c. UPJ obstruction and nonobstructing calculi in a 35-year-old man. (a, b) Axial unenhanced (a) and excretory-phase (b) CT scans demonstrate right hydronephrosis with thickening of the urothelium in the renal pelvis (arrowheads). Note the calculi layering in the collecting system (arrows in a). (c) Three-dimensional VR image of the collecting systems demonstrates right hydronephrosis due to UPJ obstruction. Note that the left renal collecting system is incompletely distended.