[Assessment of obstructive nephropathy using diuretic 99mTc-DTPA renogram and 99mTc-DMSA renoscintigraphy]

99mTc-DMSA and diuretic 99mTc-DTPA renoscintigraphy were performed on 51 kidneys suspected of obstructive nephropathy based on excretory urography to evaluate the residual renal function and the degree of urinary flow impairment respectively. We classified the response to diuretics into 6 patterns: I. normal, IIa. severely damaged renal function, IIb. slow RI excretion without urinary tract visualization (pattern II had no response to furosemide), IIIa. rapid elimination of tracer from the obstructed upper tract, IIIb. slow elimination, and IV. gradual tracer accumulation in the pelvicalyceal system with fairly well preserved renal function but no response. Hydronephrosis varied according to pattern type, in the ascending order of I, IIIa, IIIb and IV (p less than 0.05). Degree of hydronephrosis was inversely related to 99mTc-DMSA uptake, but without statistical significance. 99mTc-DMSA uptake was lower for pattern III as a whole (IIIa + (IIIb) than for pattern I (p less than 0.005), but there was no difference between IIIa and IIIb. Pattern IIa exhibited a significantly lower uptake than any of the other groups. (p less than 0.005) In contrast to previous views, we believe that pattern IIIa indicates a mild obstruction of urinary flow and impaired renal function. Consequently, assessment of obstructive nephropathy should not be based only on urodynamic study but also on differential renal function test.