Background: Urinary Tract Infection (UTI) is one of the major etiological factors of permanent kidney impairment, resulting in renal scarring and severe and pernicious side effects, such as arterial hypertension and renal failure. The purpose of this study was to clarify the impression of renal parenchyma involvement by first UTI (on the basis of acute DMSA scan) and vesicoureteral reflux (VUR-on the basis of VCUG/ RNC) on the renal scar formation (on the basis of late DMSA scan).

Methods: Children diagnosed with their first UTI at the Children's Hospital Medical Center, Tehran, Iran, were evaluated. For each patient, we recorded age, sex, results of VCUG/RNCs and acute DMSA scan, as well as those of a late DMSA scan performed 4-6 months later. The results of acute and late DMSA scans were compared along with the results of VCUG/RNCs.

Results: This study included a total of 103 children, of whom 16 (15.5%) were boys and 87 (84.5%) were girls. The mean age was 27.2±27.7 months. The frequency of renal scars in kidneys with mild (28.6%, 8.7%) and moderate (33.3%, 18.2%) pyelonephritis with or without VUR was not significantly different, while the frequency of renal scars in kidneys with severe pyelonephritis (84.6%, 23.1%) in the presence of VUR was significantly higher than non-refluxing kidneys with severe pyelonephritis (p=0.005). Furthermore, the frequency of renal scars in refluxing kidneys increased significantly with the severity of pyelonephritis (normal 8.3%, mild 28.6%, moderate 33.3%, and severe 84.6%; p=0.001). This pattern was not significant in non-refluxing kidneys (0%, 10.3%, 18.2%, and 23.1%, respectively; p=0.062).

Conclusion: The present study indicates that the incidence of renal scarring increases with pyelonephritis severity in patients with VUR. Furthermore, we can estimate the risk of renal scar formation from the results of acute DMSA scan and VCUG/RNC.