Dynamic contrast-enhanced MR renography for renal function evaluation in ureteropelvic junction obstruction: feasibility study.

OBJECTIVE The purpose of this study was to evaluate split renal function, estimate single-kidney renal function, and identify cause of obstruction in patients with ureteropelvic junction (UPJ) obstruction by using contrast-enhanced dynamic MR renography (MRR). MATERIALS AND METHODS Seventeen patients with UPJ obstruction underwent MRR and diuresis nuclear renography. Nuclear renography assessment of split renal function and mechanical versus functional obstruction served as the reference standard. The Baumann-Rudin model for determining glomerular filtration rate (GFR) was applied to generate single-kidney renal function (SK-GFRMRR) from MRR cortical and medullary enhancement curves. MRR split renal function of the right kidney (SK-GFRMRR of the right kidney normalized to the sum of SK-GFRMRR of both kidneys) was compared with nuclear renography. The MRR estimate of total GFR (eGFRMRR) was compared with that derived from Modification of Diet in Renal Disease (MDRD) formula (eGFRMDRD). Renal pelvic rate of signal intensity change (PUR) was compared between functionally and mechanically obstructed kidneys. RESULTS There was excellent correlation between MRR and nuclear renography measure of split renal function ratio (r = 0.87, p < 0.01), with mean difference of less than 10%. There was moderate correlation (r = 0.60, p = 0.01) between eGFRMRR and eGFRMDRD. eGFRMRR underestimated eGFRMDRD, with mean difference of 13.3 mL/min/1.73 m(2). PUR in mechanically obstructed units was significantly lower (0.39 ± 0.26 vs 2.0 ± 1.38 min(-1); p < 0.01) compared with functionally obstructed units. PUR discriminated mechanical from functional obstruction with accuracy of 89%. CONCLUSION In patients with UPJ obstruction, MRR can measure split renal function, estimate eGFRMDRD with moderate correlation, and accurately discriminate mechanical from functional obstruction, thus potentially providing a "one-stop shop" examination.