Accessory renal arteries in prenatal hydronephrosis as a pathophysiologic contributor or incidental vascular finding: a prospective observational study.

BACKGROUND: Accessory renal arteries (ARAs) are recognized as an extrinsic cause of hydronephrosis in children; however, their relationship with prenatally detected hydronephrosis remains unclear. This prospective study aimed to evaluate the prevalence and Doppler characteristics of ARAs in fetuses with antenatal hydronephrosis and to compare renal morphologic and vascular parameters with those of a control group. METHODS: This prospective observational study included 123 singleton pregnancies between 18 and 36 weeks' gestation. Fetuses were classified into a hydronephrosis group (n = 67) and a control group with normal renal anatomy (n = 56). Renal morphologic measurements and standardized renal vascular Doppler examinations were performed in all cases. The presence of ARAs was assessed using color and spectral Doppler imaging. RESULTS: ARAs were more frequently detected in the hydronephrosis group than in controls (10.4% vs. 3.6%), although the difference was not statistically significant (p = 0.180). No significant differences were found in renal pelvic anteroposterior diameters (right: p = 0.42; left: p = 0.39), renal volumes (right: p = 0.67; left: p = 0.71), or main renal artery pulsatility indices (right: p = 0.332; left: p = 0.258), between fetuses with and without ARAs in either the hydronephrosis or control groups. CONCLUSIONS: ARAs were more frequently observed in fetuses with hydronephrosis than in controls; however, this difference did not reach statistical significance. Furthermore, no significant differences were observed in renal morphology or main renal artery hemodynamic parameters according to ARA status during fetal life. These findings suggest that ARAs may represent a variant of renal vascular anatomy rather than a pathological burden in the prenatal setting.