Establishment of normal reference range of total and separate glomerular filtration rate in living potential kidney donors by Gates’ method after renal depth measured using SPECT/CT

Background: The underestimation of renal depth by Tønnesen formula in Gates’ method has been confirmed by most scholars, which leads to the underestimation of total glomerular filtration rate measured by Gates’ method (gTGFR) and separate glomerular filtration rate measured by Gates’ method (gSGFR). This study is to establish the normal reference range of renal depth-calibrated gTGFR and gSGFR in Chinese healthy adults, and to analyse the influencing factors.

Methods: Renal depth was measured by CT scan before 99mTc-Diethylene triamine pentacetic acid renal dynamic imaging was performed by SPECT/CT in 329 living kidney donors. The distance from the skin of the back to the anterior or posterior surfaces of each kidney at the level of renal hilum, and the average of these two values was calculated to obtain the renal depth of each kidney (see Figure 1). The renal depth-calibrated gTGFR and gSGFR was calculated by Gates’ method using renal depth measured by CT instead of calculated by the Tønnesen formula. A general linear model based on age, gender, body height, body weight and body mass index (BMI) was used to analyze the influence factors of gSGFR and gTGFR.

Results: 1,The average gSGFR and gTGFR of 23~64 years old were 49.6 ± 10.2 and 99.1 ± 18.7 ml/min/1.73 m², respectively. The gSGFR (L), gSGFR (R) and gTGFR were 26.9~69.3, 27.7~68.9, 57.5~135.3 ml/min/1.73 m² at 41~50 years old, and 31.0~61.5, 29.5~63.3, 64.6~120.7 ml/min/1.73 m² at 51-60 years old, respectively (see Table 1, 2). 2,the 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 the age increased by one year, the gSGFR (L), gSGFR (R) and gTGFR decreased by 0.17, 0.28, 0.44 ml/min/1.73 m², while for every 1 cm increased in body height, the gSGFR (L), gSGFR (R) and gTGFR decreased by 0.37, 0.36 and 0.74 ml/min/1.73 m², respectively.

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

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