Teenager with left flank pain

CT of renal stone at ureteropelvic junction
Axial CT without contrast of the abdomen (above left) shows a hydronephrotic left kidney with a small amount of perinephric fat stranding. There is a high density calcification associated with the inferior aspect of the left kidney (below left) that on the sagittal image (right) is seen to be at the left of the ureteropelvic junction.

The diagnosis was a renal stone at the left ureteropelvic junction.