Figure 5.
MR nephrography of a 3-year-old boy with ureteropelvic junction obstruction on the left side and megaureter on the right side owing to vesicoureteral reflux. Reduced kidney function was found on the left side with a differential renal function of 76%:24% owing to newly decompensated ureteropelvic junction obstruction confirmed by mercaptoacetyltriglycine (MAG3) scintigraphy (second scintigraphy; dark line, left kidney; light line, right kidney). The former scintigraphy of this patient 4 months ago had demonstrated only a functional obstruction with a diuretic half-time (t1/2) shorter than 20 min (first scintigraphy; dark line, left kidney; light line, right kidney). The discrepancy in differential renal function between MRI and MAG3 may be caused by the different mechanism of excretion (glomerular filtration/tubular secretion). CM, contrast media; MRU, MR urography.