Establishment of normal reference ranges for total and separate glomerular filtration rates in living kidney donors by Gates' method after renal depth measured using single-photon emission computed tomography/computed tomography.

Background: The underestimation of renal depth by Tønnesen formula in Gates' method, which has been confirmed by many scholars, leads to the underestimation of both separate glomerular filtration rate (gSGFR) and total glomerular filtration rate (gTGFR). This study aimed to establish the normal reference ranges of renal depth-calibrated gTGFR and gSGFR in Chinese healthy adults, and to analyze the influencing factors.

Methods: Renal depth was measured by CT scan followed by technetium 99m-diethylene triamine pentaacetic acid (Tc-DTPA) renal dynamic imaging by single-photon emission computed tomography/computed tomography (SPECT/CT) in 329 living kidney donors. The renal depth-calibrated gTGFR and gSGFR were calculated by Gates' method with renal depth measured by CT instead of being calculated by the Tønnesen formula. A general linear model based on age, gender, body height, body weight, and BMI was used to analyze factors influencing gSGFR (L), gSGFR (R) and gTGFR.

Results: The average gSGFR (L), gSGFR (R), and gTGFR for patients aged 23-64 years old were 49.3±10.1, 49.9±10.4, and 99.1±18.7 mL/min/1.73 m, respectively. The gSGFR (L), gSGFR (R) and gTGFR for patients aged 41-50 years old were 26.9-69.3, 27.7-68.8, and 57.5-135.3 mL/min/1.73 m, respectively, and those for patients aged 51-60 years old were 31.0-61.5, 29.5-63.3, and 64.6-120.7 mL/min/1.73 m, respectively. gSGFR (L), gSGFR (R) and gTGFR had statistical significance with body height and age (P<0.05); however, there was no significant difference with gender, body weight, and BMI (P>0.05). For each 1 year increase in age, the gSGFR (L), gSGFR (R), and gTGFR decreased by 0.17, 0.28, and 0.44 mL/min/1.73 m, respectively, while for every 1 cm increase in body height, the gSGFR (L), gSGFR (R), and gTGFR decreased by 0.37, 0.36, and 0.74 mL/min/1.73 m, respectively.

Conclusions: Normal reference ranges for renal depth-calibrated gSGFR (L), gSGFR (R), and gTGFR were established in healthy Chinese adults aged 23-64 years, and gSGFR (L), gSGFR (R), and gTGFR decreased with age and body height.