(99m)Tc-DTPA dynamic SPECT and CT volumetry for measuring split renal function in live kidney donors.

Objectives: Split renal function (SRF) estimated from the posterior view of (99m)Tc-diethylenetriaminepentaacetic acid planar scintigraphy (DTPA/P) is not sufficiently accurate even after correction for kidney depth by computed tomography (CT). To obtain more accurate SRF using (99m)Tc-DTPA, dynamic SPECT method was carried out for the initial 5 min after bolus injection of (99m)Tc-DTPA (DTPA/SPECT). Also SRF was evaluated from the renal volume measured by CT. We compared the results with (99m)Tc-dimercaptosuccinic acid SPECT (DMSA/SPECT).

Methods: In 60 consecutive live kidney donors, 30 DTPA/P, 30 DTPA/SPECT, 60 (99m)Tc-DMSA/SPECT, and 60 CT studies were performed. In the DTPA/P studies, SRF was calculated from the posterior image recorded during 2-3-min postinjection with attenuation correction for kidney depth measured by CT. In the DTPA/SPECT studies, SPECT images were acquired continuously for 5 min with a dual-headed gamma camera. In (99m)Tc-DMSA scintigraphy, DMSA/SPECT images were acquired 3-h postinjection. The SRF on both SPECT studies was calculated from the total counts of each kidney. In the DTPA/SPECT study, SRF was evaluated on the three images summed for 1 min: 1-2 min (DTPA/SPECT1-2), 2-3 min (DTPA/SPECT2-3), and 1-3 min (DTPA/SPECT1-3). In the CT examination, to assess the global renal volume, the axial images in the excretory phase were chosen. Renal contours were identified on each image, and the areas (cm(2)) of these regions were summed and multiplied by the slice thickness (10 mm) to yield global renal volume (ml). Right renal function from DTPA/P, DTPA/SPECT, and CT were compared with that from DMSA/SPECT as a reference.

Results: Correlation coefficients of the right renal function between DMSA/SPECT and DTPA/P, DTPA/SPECT2-3, and CT were 0.663, 0.849 and 0.907, respectively (P < 0.0001). The differences between DMSA/SPECT and DTPA/P, DTPA/SPECT2-3 and CT were 2.42 +/- 3.878, 0.867 +/- 1.672, and -0.421 +/- 1.077% (mean +/- SD), respectively.

Conclusion: SRF derived from DTPA/SPECT showed a better correlation with DMSA/SPECT and significantly fewer errors (P < 0.05) than DTPA/P. A significant strong correlation was observed between SRF from DMSA/SPECT and CT, indicating the utility of CT renal volumetry for evaluating SRF.