The relationship between glomerular filtration rate and per unit renal volume in infants with congenital hydronephrosis measured by static renal imaging and Ultrasonography
Authors: Zhao Deshan , Guo Ke 
Published: April 2023

Abstract
Objective：To observe the relationship between GFR and unit volume in single kidney in infants with congenital hydronephrosis measured by 99mTc-DMSA static renal imaging and renal ultrasonography.
Methods：According to the classification of hydronephrosis, 38 infants with congenital hydronephrosis within 12 months were divided into six groups: normal left and right kidney groups, mild hydronephrosis left and right kidney groups, and severe hydronephrosis left and right kidney groups. Within one week, all patients received ultrasonic examination, diuretic dynamic renal imaging and static renal imaging respectively, and lateral imagings of both kidneys was performed after static renal imaging. The length,width and thickness of kidneys measured by ultrasound and static renal imaging were substituted into the improvement formula of pediatric renal volume:length×width×thickness×0.674, respectively, to obtain the renal volumes in groups,and the renal function in per unit volume (GFR/unit volume, ml/cm3) was calculated. Paired t test was used for data, and p<0.05 was considered significant statistically. Pearson correlation analysis was performed for kidney volume measured by ultrasonography and corresponding GFR of single kidney in six groups, and respective regression equations were obtained.
Results：The length,width and volume of left and right kidneys in normal groups and mild hydronephrosis groups measured by static renal imaging were slightly larger than those from ultrasound, while the renal function in per unit volume were smaller than those measured by ultrasound. On the contrary, the length,width and volume of left and right kidneys in severe hydronephrosis groups were slightly smaller than those from ultrasound, while the renal function in per unit volume were larger than those measured by ultrasound, and the results among all groups had statistical differences (p<0.05). The smallest renal function in per unit volume in kidney with normal function was 1.62ml/cm3（left kidney）in static renal imaging, but the largest renal function in per unit volume in kidney with normal function was 2.20ml/cm3（right kidney）in ultrasonography,and the renal function in per unit volume was significantly higher in right kidney than in left kidney.There were a highly positive correlation between GFR and renal volume in normal left kidney group and mild hydronephrosis left and right kidney groups (normal left kidney group: r=0.865, mild hydronephrosis left kidney group:r=0.872,mild hydronephrosis right kidney group:r=0.822).There were a moderate positive correlation between GFR and renal volume in normal right kidney group and severe hydronephrosis left and right kidney groups (normal right kidney group: r=0.783, severe hydronephrosis left kidney group:r=0.542,severe hydronephrosis right kidney group:r=0.798). There were a linear relationship between GFR and renal volume measured by ultrasonography in groups,and linear regression equations in groups were obtained.
Conclusion：The GFR in per unit volume of kidney with normal function was about 1.62-2.20ml/cm3, which was significantly higher in right kidney than in left kidney,and that in kidneys with hydronephrosis also decreased with the gradual aggravated hydronephrosis.