Objective: 99mTc-p-aminohippuric acid (PAH) is a new radiopharmaceutical rapidly secreted by the kidneys in a manner consistent with tubular secretion. A comparative study of renal scintigraphy and clearance with 99mTc-PAH, diethylene triamine pentaacetic acid (DTPA) and mercaptoacetyltriglycine (MAG,) was performed.
Methods: 99mTc-PAH was prepared from a lyophilized kit by addition of sodium pertechnetate in the presence of DTPA. Ten healthy individuals were injected with 110 MBq of 99mTc-PAH. A dynamic study was repeated with 99mTc-DTPA and 99mTc-MAG3 several days later, after a 1-day interval. Clearance measurements were performed in five individuals.
Results: The mean values of time-to-peak activity (Tmax) and the time from peak to 50% of peak activity (T(1/2)) for 99mTc-PAH (3.6 +/- 0.9 and 6.9 +/- 2.7 min, respectively) and 99mTc-MAG3 (3.5 +/- 0.8 and 6.8 +/- 2.1 min, respectively) were significantly lower in comparison with those of s99mTc-DTPA (4.9 1.7 and 11.7 +/- 1.9 min, respectively). The mean value of 99mTc-PAH clearance (186.9 +/- 12.2 ml/min) was significantly lower in comparison with MAG3 clearance (303.9 +/- 19.5 ml/min) and significantly higher than DTPA clearance (85.0 +/- 24.1 ml/min).
Conclusion: Our preliminary results indicate the potential usefulness of 99mTc-PAH for routine renal scintigraphy. Owing to its fast kinetics, excretion properties and high-quality images, it could be a suitable substitute for 99mTc-DTPA. 99mTC-PAH clearance values, however, were significantly lower than those of MAG3, and could not be used for the estimation of renal plasma flow.