DIFFERENTIAL RENAL-FUNCTION MEASURED BY TC-99(M)-DTPA AND TC-99(M)-DMSA IN A COMPLETE UNILATERAL RENAL OBSTRUCTION RAT MODEL

We performed a prospective study to determine whether Tc-99(m)-DTPA di fferential 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 recir culation or a block of tubular transport of DMSA which might explain t he discrepancy reported by Kelleher et al. [1]. In 15 male and 4 femal e Wistar rats (weight 300-350 g), Tc-99(m)-DMSA renal uptake was measu red 24 h before complete obstruction of the right ureter, which served as reference values. Twenty-four hours after obstruction, Tc-99(m)-DT PA (18.5 MBq) renography and Tc-99(m)-DMSA (111 MBq) non-depth-correct ed renal uptake measurements were performed in the 15 male rats; in th e 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 ob struction, whereas Tc-99(m)-DTPA DRF ranged from 16 to 30% (mu: 25%; s igma: 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 o bstructed 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 o f Kelleher et al. [1] may be due to intratubular pressure. In conclusi on, the present findings and those of Kelleher et al. suggest the diff erences in DRF following complete unilateral renal obstruction, as det ermined by DTPA and DMSA, are probably species-specific. Furthermore, recirculation and block of tubular transport are unlikely to contribut e significantly to differences in DRF as measured by the two radiophar maceuticals.