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Overview of fetal hydronephrosis

Laurence S Baskin, MD, FAAP
Section Editors
Tej K Mattoo, MD, DCH, FRCP
Louise Wilkins-Haug, MD, PhD
Duncan Wilcox, MD
Deputy Editor
Melanie S Kim, MD


Fetal hydronephrosis (dilation of the renal pelvis with or without dilation of the renal calyces) is a common finding on antenatal ultrasound [1,2]. In most cases, renal pelvic dilation is a transient physiologic state, however, congenital anomalies of the kidney and urinary tract (CAKUT) can present with fetal hydronephrosis due to urinary tract obstruction and vesicoureteral reflux (VUR). These conditions may be associated with impaired renal development and/or cause renal injury.

Nevertheless, the majority of cases of fetal hydronephrosis are not clinically significant, and therefore excessive concern may lead to unnecessary testing of the newborn infant and anxiety for parents and health care providers. The goal of prenatal management is to detect those cases of fetal hydronephrosis that may adversely affect the health of the infant and require antenatal and postnatal evaluation, timely referral to a pediatric urologist if required, and possible intervention to minimize adverse outcomes, while limiting testing in those cases that are due to a benign, transient condition.

The definition, etiology, and management of fetal hydronephrosis are reviewed here. Postnatal evaluation of fetal hydronephrosis and specific urologic conditions that may present as fetal hydronephrosis are discussed separately. (See "Postnatal management of fetal hydronephrosis" and "Congenital ureteropelvic junction obstruction" and "Primary megaureter in infants and children" and "Ectopic ureter" and "Clinical presentation and diagnosis of posterior urethral valves", section on 'Prenatal' and "Clinical presentation, diagnosis, and course of primary vesicoureteral reflux".)


Several systems have been developed to diagnose and grade the severity of fetal hydronephrosis [3]. There is no consensus on the most appropriate grading criteria for the diagnosis of fetal hydronephrosis [4]. In general, the likelihood of having a significant renal anomaly correlates with the severity of hydronephrosis.

Scoring systems differ based upon the fetal ultrasound criteria used and include:

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Literature review current through: Nov 2017. | This topic last updated: Apr 25, 2017.
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