CONTRADICTORY SUPRANORMAL NUCLEAR RENOGRAPHIC DIFFERENTIAL RENAL-FUNCTION - FACT OR ARTIFACT

We previously reported contradictory supranormal nuclear renographic d ifferential renal function in cases of unilateral hydroureteronephrosi s, in which the kidneys with hydroureteronephrosis paradoxically had a greater differential function than the contralateral normal mate, bas ed on diethylenetriaminepentaacetic acid (DTPA) nuclear renography. To evaluate whether DTPA supranormal differential function represented t rue hyperfunction, patients with DTPA supranormal differential functio n were evaluated with dimercaptosuccinic acid (DMSA) nuclear renograph y and the results were compared. A total of 16 patients with unilatera l hydronephrosis was identified to have DTPA differential function of 53% or more, They were younger than age 1 year and had never undergone any urological surgery, In all 16 patients the DMSA differential func tion (mean 51.1%, range 42 to 57%) was lower than their own correspond ing DTPA differential function (mean 58.3%, range 53 to 66%, p < 0.000 1). In addition, the DMSA differential function was not significantly different from the intuitively anticipated mean of 50% (p = 0.48). The DTPA supranormal differential function identified in our patients was not corroborated, by the DMSA differential function, With recent evid ence that DMSA differential function may be a better predictor of outc ome following relief of unilateral ureteral obstruction consideration should be given to using DMSA as a potentially more relevant method fo r differential function measurement in the setting of unilateral hydro nephrosis. Conversely, until the potential deficiencies of DTPA are fu lly understood caution should be exercised in the interpretation of DT PA differential function in the setting of hydronephrosis.