Evaluation of renal functional reserve in primary vesicoureteric reflux: A cross-sectional study

The role of renal functional reserve (RFR) in children with vesicoureteric reflux (VUR) is understudied. The objective of this study was to determine RFR [assessed by Diethylenetriaminepentaacetic acid (DTPA) scan] in patients aged 2-18 years with primary VUR.

This cross-sectional study evaluated RFR in 50 children with primary VUR. Baseline and stimulated (after 1 g/kg protein meal) GFR were measured using technetium-99m (Tc-99m) DTPA plasma clearance (Russell's two-sample method). RFR was calculated as the proportional GFR increase, with >10% defined as positive RFR and compared across grades of VUR and scars. RFR was also assessed by timed urinary creatinine clearance.

The median age at RFR estimation was 4.3 [IQR:2.9, 8.1] years, while median age-at-diagnosis was 7 [2, 24] months. The median duration of illness was 3.6 [2.3, 6.2] years. Initial presentations included urinary tract infections (UTI) in 31 (62%) children and antenatal hydronephrosis in 18 (36%), with 90% (n = 45) having a history of prior pyelonephritis. Patients were categorized by VUR severity: unilateral low-grade (n = 7; 14%), unilateral high-grade (n = 14; 28%), bilateral high-grade (n = 26; 52%), and bilateral low-grade (n = 3; 6%). The median DTPA RFR was 13.67 [5.84, 28.27]%, with 60% (n = 30) demonstrating a positive RFR. RFR compared among children with low-grade vs high-grade VUR, demonstrated no statistically significant difference (p = 0.28). DTPA-RFR correlated weakly with timed creatinine clearance RFR (r = 0.20), which consistently overestimated RFR. The median-annual-decline rate was higher in group with absent RFR (-4.2 vs improvement of 18.25 mL/min/1.73 m²/year), with a median difference of 22.45 mL/min/1.73 m²/year (bootstrap 95% CI 4.58, 60.74), p = 0.011.

In conclusion, preserved RFR was noted in nearly two-thirds of children with VUR, with no significant difference with disease severity. The study demonstrates that RFR can be measured using different methodologies in children with VUR and provides valuable feasibility data.