The etiology of renal scars in infants with pyelonephritis and vesicoureteral reflux

We aimed to investigate, by means of dimercaptosuccinic acid (DMSA) scan, t he relations between vesicoureteral reflux (WR) and its degree, pyelonephri tis during infancy, and renal parenchymal findings. Seventy four infants wi th pyelonephritis, 44 girls and 30 boys (mean age at their first pyelonephr itic episode 4.12 months, median 3 months), were enrolled in the study. Voi ding cystourethrography (VCU) and ultrasonography (US) were performed withi n 6 weeks following the infection. DMSA was performed at least 4 months aft er the urinary tract infection (UTI). The renal parenchymal pathology was d efined as focal or multifocal defects or as a split renal uptake of less th an 45%. DMSA scintigraphy revealed that 19% (14/74) of the children had ren al damage. Renal parenchymal findings were observed only when WR was presen t, and its grade was above 3/5. No abnormality was found in 51 renal units without reflux, 9 with VUR grade 1/5, and 54 with grade 2/5. Renal patholog y was observed in 9/24 renal units with VUR grade 3, 3/8 with grade 4, and 2/2 with grade 5. No correlation was found between renal parenchymal defect s and clinical presentation of the pyelonephritis, type of the microorganis m, presence of bacteremia, or the number of recurrent infections. In adequa tely treated infants, renal damage is probably due to a reflux-associated, preexisting, congenital renal parenchymal pathology and not to the inflamma tory process. We suggest that DMSA scintigraphy should not be performed rou tinely in every infant with UTI and should be reserved primarily for childr en with WR grade 3 and above.