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 coefficient (ADC) values measured by diffusion-weighted MR imaging and split renal function determined by renal scintigraphy in patients with hydronephrosis.

MATERIAL AND METHODS: Diffusion-weighted imaging on a 1.5 T MR unit and renal scintigraphy were performed in 36 patients with hydronephrosis (45 hydronephrotic kidneys, 21 non-hydronephrotic kidneys). ADC values of the individual kidneys were measured by diffusion-weighted MR imaging. Split renal function (glomerular filtration rate (GFR)) was determined by renal scintigraphy using 99mTc-DTPA. The relationship between ADC values and split GFR was examined in 66 kidneys. The hydronephrotic kidneys were further classified into three groups (severe renal dysfunction, GFR <10 ml/min, n=7; moderate 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 correlation between ADC values and split GFR (R2=0.56). On the other hand, in nonhydronephrotic kidneys, poor correlation between ADC values and split GFR was observed (R2=0.08). The mean values for ADCs of the dysfunctioning hydronephrotic kidneys (severe renal dysfunction, 1.32 x 10(-3) +/- 0.18 x 10(-3) mm2/s; moderate renal dysfunction, 1.38 x 10(-3) +/- 0.10 x 10(-3) mm2/s) were significantly lower than that of the normal functioning hydronephrotic kidneys (1.63 x 10(-3) +/- 0.12 +/- 10(-3) mm2/s).

CONCLUSION: These results indicated that measurement of ADC values by diffusion-weighted MR imaging has a potential value in the evaluation of the functional status of hydronephrotic kidneys.