The clinical significance of severe unilateral antenatal hydronephrosis

Abstract

Background and objective Antenatal hydronephrosis (ANH) is one of the most common birth abnormalities and is defined as foetal renal pelvis dilatation > 4 mm before 33 weeks and 7 mm before 40 weeks gestation. Foetal pelvis AP diameter exceeding 14 mm is classified as severe hydronephrosis. It remains unclear at what degree of hydronephrosis should further investigations be initiated after birth. The objective of this study was to review the postnatal outcome of severe unilateral antenatal hydronephrosis with /or without hydroureter. Method Retrospective identification of pregnant mothers referred to the foetal medicine department between Jan 2003- June 2008, linkage of their babies through the Congenital Anomaly Register and Information Service database, analysis of the children's investigations and treatments at the University Hospital in Wales. Result Of the 61 pregnancies referred antenatally, 40 case notes were retrospectively reviewed to assess postnatal outcome. 21 cases were excluded (no baby notes /deaths /born outside Wales). Benefit of antenatal surgery performed on 4 cases with pelvic aspirations and pigtail catheter insertion proved unfruitful as three resulted in single functioning kidney and one had persisting hydronephrosis. Significant discrepancy in antenatal and postnatal scan results was noted (22/40) leading to a different postnatal diagnosis. Urogenital obstruction (12/40), vesico ureteric reflux (7/40), ureterocele (5/40) and duplex kidneys (4/40) were common. Surgical interventions was performed in 21/40 cases and included puncture or excision of ureteroceles, ureteric reimplantation, heminephrectomy and treatment of obstruction. Urinary tract infections (15/40) were often recurrent despite oral prophylactic antibiotic. Overall, 13/40 cases had a single functioning kidney. High association with other congenital anomalies such as imperforate anus, cardiac problems, Turner Syndrome, VACTERL association, cerebral and lumbo- sacral abnormalities were seen. Conclusion Unilateral severe antenatal hydronephrosis of more than 14 mm with or without hydroureter is associated with congenital anomalies and significant pathology leading to surgery, UTI or non-functioning kidney. Foetal interventions did not improve outcome. Diagnosis may be inaccurate with discrepancy in antenatal and postnatal scan results. These cases warrant careful postnatal examination and further investigations. This information could be used in prenatal counselling and to plan postnatal management with an aim to minimise complications.