PURPOSE: Infants with history of antenatal hydronephrosis and neonatal vesicoureteral reflux may have detectable changes in renal scans before the advent of urinary tract infection. In cases of bilateral high-grade vesicoureteral reflux, differential renal function on renal scan may not reveal renal hypoplasia since comparison of relative function may be made between two abnormal kidneys. We tested the hypothesis that ultrasonography in the neonatal period may be accurate and complementary to renal scan in detecting renal hypoplasia at birth.
Twenty-six infants who presented in the antenatal period with history of hydronephrosis and were noted to have neonatal vesicoureteral reflux postnatally were studied retrospectively. They had all been treated by a prospective protocol that included renal ultrasound and renal scans in the first 6 weeks of life. All had been placed on prophylactic antibiotics and had no urinary tract infection. Multiple sonographic parameters were analyzed including kidney length, echogenicity, calyceal blunting, parenchymal thinning and focal scars. We correlated the renal morphology on ultrasound, the renal function on renal scan and the degree of reflux seen on VCUG.
VCUG showed reflux in 44 renal units, grade of reflux was: I (2), II (7), III (12), IV (8), and V (15). A variety of nucleides were used including DMSA in 15, DTPA in 6 and MAGIII in 5. Renal scans identified global hypoplasia without focal scars (differential function less than 40%) in 10 of 44 refluxing renal units grades I (1), III (2), IV (4), and V (3). The sonographic finding of decreased renal length (<50th percentile for age) was present in 14 refluxing units of 44 refluxing renal units, grade I (1), grade III (4 bilaterally in 1), grade IV (4 bilaterally in 1), and grade V (5 bilaterally in 2). The sonographic finding of decreased renal length (<50th percentile) correlated strongly with renal hypoplasia on renal scans in refluxing renal units (p value < .005, sensitivity 80% and specificity 82%, positive predictive value 57%, and negative predictive value 93%).
Postnatal ultrasonography is a reliable measure of gross renal parenchyma, and in the presence of vesicoureteral reflux correlates with renal scintilligraphy. In addition, for cases of bilateral neonatal vesicoureteral reflux, ultrasound and renal scan are complimentary, each being able to detect the abnormalities that might be missed by the other.