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

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(before) = 0.967 versus r(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.