Functional evaluation of hydronephrosis by diffusion-weighted MR imaging -Relationship between apparent diffusion coefficient and split glomerular filtration rate

Purpose: To determine the relationship between apparent diffusion coefficie nt (ADC) values measured by diffusion-weighted MR imaging and split renal f unction determined by renal scintigraphy in patients with hydronephrosis. Material and Methods: Diffusion-weighted imaging on a 1.5 T MR unit and ren al scintigraphy were performed in 36 patients with hydronephrosis (45 hydro nephrotic kidneys, 21 non-hydronephrotic kidneys). ADC values of the indivi dual kidneys were measured by diffusion-weighted MR imaging. Split renal fu nction (glomerular filtration rate (GFR)) was determined by renal scintigra phy using Tc-99m-DTPA. The relationship between ADC values and split GFR wa s examined in 66 kidneys. The hydronephrotic kidneys were further classifie d into three groups (severe renal dysfunction, GFR <10 ml/min, n=7; moderat e renal dysfunction, GFR 10-25 ml/min, n=10; normal renal function, GFR >25 ml/min, n=28), and mean values for ADCs were calculated. Results: In hydronephrotic kidneys, there was a moderate positive correlati on between ADC values and split GFR (R-2=0.56). On the other hand, in nonhy dronephrotic kidneys, poor correlation between ADC values and split GFR was observed (R-2=0.08). The mean values for ADCs of the dysfunctioning hydron ephrotic kidneys (severe renal dysfunction, 1.32x10(-3)+/-0.18x10(-3) mm(2) /s; moderate renal dysfunction, 1.38x10(-3)+/-0.10x10(-3) mm(2)/s) were sig nificantly lower than that of the normal functioning hydronephrotic kidneys (1.63x10(-3)+/-0.12+/-10(-3) mm(2)/s). Conclusion: These results indicated that measurement of ADC values by diffu sion-weighted MR imaging has a potential value in the evaluation of the fun ctional status of hydronephrotic kidneys.