Independent risk factors for renal damage in a series of primary vesicoureteral reflux: a multivariate analysis.

Aim: The aim of this study was to investigate risk factors associated with different extents of renal parenchyma involvement in a paediatric series of primary vesicoureteral reflux (VUR).
Methods: A total of 549 patients with VUR were analyzed. The variable of interest was renal scar, assessed by technetium-99m dimercaptosuccinic acid scan, and classified into three subtypes: focal scar, multiple cortical scarring and diffuse scars with a contracted renal unit. The multinomial regression model was applied to identify independent variables associated with each subtype of renal damage.
Results: After adjustment, four variables remained independently associated with a contracted renal unit: reflux grades III-V (odds ratio (OR)=9.7; 95% confidence interval (CI) = 4.1-21.0), age at diagnosis (OR=3; 95% CI=1.6-5.1), unilateral reflux (OR=2.1; 95% CI=1.2-3.8), and male sex (OR=2; 95% CI=1.1-3.8). Two variables were associated with multiple scars: reflux grades III-V (OR=13.8; 95% CI=7.4-26.0) and age at diagnosis (OR=1.9; 95% CI=1.2-3.0). Two variables were associated with a focal scar: reflux grades III-V (OR=7.9, 95% CI CI=3.8-16.4) and male sex as a protective factor (OR=0.5; 95% CI=0.25-1.0).
Conclusion: Our findings suggest that the development of a contracted renal unit is probably due to congenital malformation, more commonly observed in male infants with high-grade reflux.