Routine Renal Scintigraphy with Sequential Injections of Technetium-99m-DTPA and Technetium-99m-MAG3

Objective: To evaluate the use of sequential injections of 99mTc-diethylene-triaminepentaacetic acid (DTPA) and 99mTc-mercaptoacetyltriglycine (MAG3) for routine renal scintigraphy. Method: Seventy-two sequential renograms were performed on 49 patients. After administration of 1 mCi of 99mTc-DTPA, data were collected for 7 min and 10 mCi of 99mTc-MAG3 were then injected. In 28 patients, furosemide was injected before 99mTc-MAG3. The time to reach peak activity, fractional renal function and retained cortical activity were calculated from the renogram curves. The total duration of the study was 30 min. The studies were analyzed by two independent observers. The GFR and ERPF were calculated using the RUPV method. Results: There were six discrepant results for time to peak activity determination due to improper selection of the initial time (time = 0) or the peak activity. The discrepancies were corrected by setting the time = 0 to the first appearance of activity in the abdominal aorta above the kidneys and by selecting the last point in flat renogram curves or in curves with no distinguishable peak activity. The use of a diuretic prior to the administration of 99mTc-MAG3 resulted in further improvement of the interobserver agreement. Conclusion: The sequential renogram is simple to perform, and provides excellent scintigraphic images and accurate functional evaluation of the kidneys using conventional gamma camera techniques.