Background: Direct radionuclide cystography (DRC) has the advantage of high sensitivity and low gonadal radiation exposure for the detection of vesicoureteral reflux (VUR), while renal cortical scintigraphy (RCS) is
a highly sensitive and specific method for detecting renal cortical abnormality. The purpose of this study is to determine the incidence and the relationship of VUR with APN (acute pyelonephritis) in children with first urinary tract infection (UTI) using DRC and RCS. Methods: Six hundred and three children with first UTI referred for both DRC and RCS were retrospectively studied. VUR was graded according to the DRC and
anatomic classification as mild, moderate or severe reflux. The severity of APN was defined as mild-moderate esions (less than 50% of kidney involvement) and severe lesions (equal to or greater than 50% of kidney involvement) by RCS. Chi-square test was used to determine the significance of differences of incidence and relationship between VUR and APN. Results: DRC revealed VUR in 128 of the 603 (21.2%)
children, while RCS revealed APN in 264 of the 603 (43.8%) children. APN was more likely to occur in children with documented VUR (68% vs. 37.3%,
P < 0.0001) and refluxing kidneys (80% vs. 20%,P < 0.0001), and most of the unilateral VUR (95%) had ipsilateral APN. Severe VUR was strongly associated with the presence of APN, while severe APN was also significantly associated with the presence of VUR. Conclusion: The incidence of VUR after first UTI in Taiwan is in between the white and black children. APN is strongly associated with the presence of VUR and its. Our data confirm that VUR, especially severe reflux, when present, continues to be a significant risk factor in the etiology and severity of childhood pyelonephritis, but that the presence of VUR by itself
does not necessarily imply an APN.