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Do babies with isolated single umbilical artery require routine postnatal renal ultrasonography?

Presented at the Neonatal Society 2007 Summer Meeting (programme).

Jog S, Watson H, Deshpande S

Royal Shrewsbury hospital, Shrewsbury SY3 8XQ, UK

Background: Presence of a single umbilical artery (SUA) is recognised as a soft marker for adverse perinatal outcome (1). An increased incidence of renal anomalies has been reported even in association with isolated SUA, and many recent studies recommend routine postnatal renal ultrasonography in such infants (2). Whether such renal imaging of otherwise well infants with isolated SUA offers any advantage in the era of now routine antenatal fetal sonography is not known.

Aims: To determine the prevalence of significant renal anomalies in infants with isolated SUA.

Methods: Babies born at the Royal Shrewsbury Hospital between 1 January 2000 and 31 December 2006 with SUA detected either on antenatal ultrasound scans or postnatal examination of the cord and/or placenta were offered routine renal ultrasonography. Babies with known chromosomal abnormalities or associated major malformations were excluded from the study. Postnatal ultrasonography was performed at 4-8 weeks of age by a team of experienced paediatric sonographers. This retrospective study was approved by the local research ethics committee, and undertaken in accordance with the UK ethical guidelines.

Results: During the study period, there were 33,067 live births, and 137 (4.1/1000) infants were found to have SUA. Eight infants had major congenital malformations (complex cardiac disease 3, cloacal anomaly 2, cystic adenomatoid malformation 1, anorectal malformation 1, chromosomal 1). Gestational age and birth weight were significantly lower among infants with isolated SUA compared to those without (mean [SD] gestation 38.4 [2.8] vs 39.2 [2.1], p=0.0024; birth weight, g 3081 [793] vs 3367 [629], p<0.0001). Infants with isolated SUA were also significantly more likely to be preterm and small for gestational age (birth weight <2 SD below mean) than those without (prematurity 15.5% vs 7.4%, p<0.0001; SGA 5.4% vs 1.9%, p<0.0001). One hundred and twenty-two (95%) of infants with isolated SUA underwent renal ultrasonography at a median (IQR) age of 49 (31-66) days. The scan was entirely normal in 117 (96%); transient abnormalities were detected in 3 infants transient unilateral renal pyelectasia (2) and simple cyst (1). Two (1.6%) infants had major anomalies single kidney and a hypoplastic kidney. The infant with single kidney did not undergo routine anomaly scan. 4/8 infants with SUA and associated malformations had concurrent renal anomalies (grade 3 vesicoureteric reflux, hydronephrosis, single kidney, and unilateral pyelectasia). The prevalence of significant renal anomalies (multicystic dysplastic kidneys, posterior urethral valves, vesicoureteric reflux >grade 2 and pyelectasia >10 mm) was similar among infants with isolated SUA and the control cohort (2 [1.6%, 95% CI 0.20-5.5] infants with isolated SUA vs 88 [0.4%, 95% CI 0.29-0.45]; p=0.074).

Conclusion: Presence of an isolated SUA is associated with an increased risk of prematurity and fetal growth restriction. In this largest series of isolated SUA, there was no excess of significant renal malformations among infants with isolated SUA. Postnatal renal ultrasonography is not routinely warranted in such infants, and should be reserved for those with other anomalies or in whom antenatal scans have shown renal abnormalities.

1. Gornall AS, Kurinczuk JJ, Konje JC. Antenatal detection of a single umbilical artery: does it matter? Prenat Diagn 2003;23:117-23. 2. Srinivasan R, Arora RS. Do well infants born with an isolated single umbilical artery need investigation? Arch Dis Child 2005;90:100-1.

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