Influence of Early Bladder Imaging in Experimental Rabbits on the Quantitative Determination of Glomerular Filtration Rate by the Gates Method

Abstract

Objective. To investigate the influence of early bladder imaging (EBI) in experimental rabbits on the quantitative calculation of glomerular filtration rate (GFR) by the Gates method. Methods. We retrospectively analyzed the data of dynamic renal scintigraphy (DRS) in experimental rabbits. We calculated renal uptake during minutes 1-2 and 2-3 by correcting bladder radioactivity and computed the split GFR by renal uptake. Then, the EBI and GFR between 1-2 min and 2-3 min were compared, respectively. Results. The EBI proportion (57.3%) at 2-3 min of DRS was higher than that (8.5%) at 1-2 min ( $P<0.05$ ). The correlations between the 1-2 min and 2-3 min uptake rates of unobstructed kidneys after correction ( $r=0.952‐0.979$ ) were higher than those before correction ( $r=0.859‐0.936$ ). However, the correlation between the two in obstructed kidneys was not improved ( $r_{\text{before}}=0.967$ versus $r_{\text{after}}=0.968$ ). For unobstructed kidneys, the difference in GFR based on 2-3 min uptake between before and after correction was significant ( $P<0.05$ ), but not in obstructed kidneys ( $P>0.05$ ). For GFR based on 1-2 min uptake, the difference between before and after correction was not significant in obstructed or unobstructed kidneys ( $P>0.05$ ). Before correction, the GFR of unobstructed kidneys of 10.5% of the rabbits in the protein load test was lower than that in the baseline status, but not so after correction. Conclusion. The 2-3 min EBI on DRS has a significant influence on the GFR calculated by the Gates method in experimental rabbits. Controlling water intake or calculating the GFR by 1-2 min renal uptake helps to avoid the influence of EBI on GFR.