Differential renal function measured by 99Tcm-DTPA and 99Tcm-DMSA in a complete unilateral renal obstruction rat model.

We performed a prospective study to determine whether Tc-99(m)-DTPA differential renal function (DRF) in the case of acute obstruction in a unipapillary kidney rat model shows a similar pattern of results as Tc-99(m)-DMSA in a multipapillary kidney model [1], and to exclude recirculation or a block of tubular transport of DMSA which might explain the discrepancy reported by Kelleher et al. [1]. In 15 male and 4 female Wistar rats (weight 300-350 g), Tc-99(m)-DMSA renal uptake was measured 24 h before complete obstruction of the right ureter, which served as reference values. Twenty-four hours after obstruction, Tc-99(m)-DTPA (18.5 MBq) renography and Tc-99(m)-DMSA (111 MBq) non-depth-corrected renal uptake measurements were performed in the 15 male rats; in the 4 female rats, 740 MBq of Tc-99(m)-DMSA were injected and absolute, non-depth-corrected renal uptake measured at 24, 48 and 72 h. Tc-99(m)-DMSA DRF of the right kidney ranged from 48 to 55% (mu: 51%; sigma: 2%) before obstruction and from 14 to 35% (mu: 24%; sigma: 6%) after obstruction, whereas Tc-99(m)-DTPA DRF ranged from 16 to 30% (mu: 25%; sigma: 4%). No significant differences were found between DRF measured by Tc-99(m)-DMSA and Tc-99(m)-DTPA (P = 0.18), or between DRF of the obstructed kidney as measured by Tc-99(m)-DMSA at 24, 48 and 72 h (P > 0.2). Hypothetically, the discrepancy between our findings and those of Kelleher et al. [1] may be due to intratubular pressure. In conclusion, the present findings and those of Kelleher et al. suggest the differences in DRF following complete unilateral renal obstruction, as determined by DTPA and DMSA, are probably species-specific. Furthermore, recirculation and block of tubular transport are unlikely to contribute significantly to differences in DRF as measured by the two radiopharmaceuticals.