2194 PREDICTING DIFFERENTIAL RENAL FUNCTION AND OBSTRUCTION WITH DYNAMIC CONTRAST-ENHANCED MR RENOGRAPHY (MRR) IN PATIENTS WITH URETEROPELVIC JUNCTION OBSTRUCTION (UPJO)

Abstract

INTRODUCTION AND OBJECTIVES: To evaluate contrastenhanced magnetic resonance renography (MRR) for evaluation of renal function in patients with ureteropelvic junction (UPJ) obstruction as it correlates with diuretic nuclear renography (NR). METHODS: 13 patients with diagnosis of UPJ underwent dynamic MRR and lasix NR. Split renal function and assessment of mechanical or function obstruction on NR served as reference. MRR was processed to generate cortical-and-medullary enhancement curves. Bauman-Rudin model was applied to generate single-kidney renal function (SK-GFR). Split renal function ratio (Obstructed SK-GFR/ Obstructed Non-obstructed SK-GFR) obtained with MRR was compared to NR. Region-of-interest placed in renal pelvis of the obstructed kidney on MRR acquisition was used to calculate upslope-rate (signalintensity change over time divided by baseline signal-intensity). This was compared between functionally and mechanically obstructed renal units. RESULTS: There was excellent correlation between MRR and NR measure of split renal function ratio (r 0.91; p 0.01) with mean difference of less than 10%. Upslope-rate in mechanically obstructed units was significantly lower than functionally obstructed units (0.38 vs. 2.18 min-1; p 0.005). Upslope-rate cutoff of 0.85 min-1 could diagnose mechanical and functional obstruction with accuracy of 92% (12/13 patients). We were also able to calculate absolute measure of renal function (MR-GFR) which underestimates eGFR calculated with the Modification in Diet in Renal Disease (MDRD) equation. CONCLUSIONS: MRR can assess split renal function and discriminate mechanical from functional obstruction with high accuracy. A ‘one-stop-shop’ MR exam may be able to replace NR due to the ability to determine type of obstruction and also provide a pre-operative road map given the ability of MR to delineate vascular and renal anatomy to aid in surgical planning.