Renal parenchymal damage in intermediate and high grade infantile vesicoureteral reflux

The association of vesicoureteral reflux, urinary tract infection and renal scarring is well recognized. We evaluated the incidence of renal parenchymal scarring in a large series of infants with primary high grade vesicoureteral reflux.

The medical records of 549 consecutive infants with primary high grade vesicoureteral reflux between 1985 and 2006 were reviewed. A total of 473 infants (86.1%) presented with febrile urinary tract infections, 63 (11.5%) were screened for sibling vesicoureteral reflux and 13 (2.4%) were investigated because of prenatally diagnosed hydronephrosis. Age at diagnosis was defined as patient age at the first voiding cystourethrogram. Renal parenchymal scarring was evaluated by dimercapto-succinic acid scan and classified into 3 groups, including mild--focal defects with between 40% and 45% relative uptake of renal radionuclide, moderate--relative uptake between 20% and 40%, and severe--a shrunken kidney with relative uptake less than 20%.

Of the 549 infants 292 (53%) were boys and 257 (47%) were girls with a median age of 6 months (range 2 to 12). Reflux was unilateral in 160 and bilateral in 389 (938 ureters). Reflux grade was II to V in 19, 372, 458 and 89 ureters, respectively. All patients with grade II reflux had high grade reflux on the contralateral side. Renal parenchymal scarring was present in 122 of the 458 infants (27%) evaluated with dimercapto-succinic scan. The incidence of renal parenchymal scarring was only 9% in infants without a history of urinary tract infection and 29% in those who presented with a urinary tract infection (p <0.01). Moderate to severe renal parenchymal scarring was present in 55 infants, of whom 73% were male and 27% were female.

The data show that moderate to severe renal scarring is associated with grade IV and V reflux, and male sex. The incidence of renal scarring is significantly lower in infants in whom high grade vesicoureteral reflux is detected by screening before the development of urinary tract infection. Early detection may prevent urinary tract infection related renal parenchymal scarring.