Comparison of Split Renal Function on DTPA Renal Scan and Endogenous Creatinine Clearance Ratio in Obstruction of Upper Urinary Tract

Chung, Hun Young; Seo, Kie Seok; Kim, Jong Sung

Abstract

PURPOSE: Split renal function on diuretic renography has been considered to be a good tool for evaluating renal function, selecting treatment modalities and assessing efficacy of surgery in hydronephrosis, especially in ureteropelvic junction(UPJ) obstruction. However, contradictory supranormal function on renography has provided controversy with urologists. Is the phenomenon the result of fact or artifact? The authers thought that contradictory supranormal renal function measured with 99mTc-DTPA Is fundamentally related with a question. How accurately does the split renal function test represent the real renal function, namely, glomerular filtration rate(GFR)? To know relation of split renal function with real renal function(GFR) and to disclose clinical significance of contradictory supranormal renal function on diuretic renal scan, a prospective study was performed.
MATERIALS AND METHODS
Diuretic renography was done in 14patients with upper urinary tract obstruction including UPJ obstruction, ureteral stone and lower urethral obstruction. Afer the first diuretic renography using 99mTc-DTPA percutaneous nephrostomy was performed on affected kidney, which was followed by the second diuretic renography. Endogenous creatinine clearance tests were done on the patients. Urine was collected through the nephrostomy tube, self voiding or indwelling Foley catheter, respectively So the endogenous creatinine clearance was determined respectively on both the renal unit. Also the endogenous creatinine clearance ratio of affected kidney was determined to compare with split renal function on renography.
RESULTS
In 7patients, ratio of endogenous creatinine clearance on affected kidney was less than 40%. In the other 7patients, the ratio was more than 48%. In patients with less than 40% of endogenous creatinine clearance ratio on affected kidney, split renal function was overestimated by 10.3% to 27.5%(19.5+/-4.9%) comparing to endogenous creatinine clearance ratio. In the other 7patients split renal function had a little difference from endogenous creatinine clearance ratio (4.5+/-2.5%). The endogenous creatinine clearance ratio was not closely related with split renal function(correlation coefficients: 0.65). Split renal function of the first renography was closely related with that of the second renography(correlation coefficients: 0.88). Contradictory supranormal function occurred in 4cases. In 2cases it was real finding, in the other it was not.
CONCLUSIONS
It appears that split renal function is overestimated in poor renal function and split renal function is closely related with real renal function in good renal function slate. Supranormal renal function is real finding in part, not in part. Clinical significance of split renal function should be cautiously and basically reevaluated through further study.