Neonatal renal ultrasound – a 5‐year review in an obstetric hospital

Abstract

Aim: To review a consecutive series of neonatal renal scans presenting to the imaging department in an obstetric hospital, record the abnormalities seen and assess the accuracy of the antenatal diagnosis with subsequent outcome.Material and methods: In the 5 years (1996–2000), there were 788 neonates referred for renal ultrasound scans. Many of the infants had a micturating cystourethrogram (MCU) at the time of presentation. The commonest indication in 92% of neonates was fetal pyelectasis reported on the antenatal scan. The hospital records of these infants were reviewed with further details obtained from clinicians and surgeons and subsequent investigations.Results: The results were classified according to the findings. There were a total of 788 neonates who had a renal scan. There were 592 (75%) in whom the scan was considered normal and of these 49 had an MCU and 17 had associated vesico‐ureteric reflux (VUR) grades 1–4. There were 125 (16%) infants with persisting mild‐moderate pyelectasis/hydronephrosis and of these 61 resolved or were lost to follow up and 64 persisted at follow up scans variably timed 3–15 months later. Most of these had an MCU and 26 had associated VUR grade 1–5, not always on the side of the pyelectasis. Miscellaneous abnormalities were seen in 71 (9%) neonates, multicysticdysplastic kidney 25, pelviureteric junction obstruction (PUJ) 7, solitary kidney 6, crossed renal ectopia 5, uncomplicated duplex kidney 5, ureterocoele 5, two with posterior urethral valves and one with vesico‐ureteric junction obstruction (VUJ). There were four infants with significant VUR, three with thinned renal parenchyma and one with a small kidney. There were three with autosomal recessive polycystic kidney disease (Potter's type II), one with small dysplastic kidneys.Conclusion: In this review, there were 113 neonates (14%) found to have significant renal anomaly or VUR. Many of the miscellaneous fetal renal abnormalities have a characteristic and identifying appearance on the antenatal ultrasound. The majority of neonatal renal scans are referred because of mild/moderate fetal pyelectasis and many of these resolve over a variable time. Persisting moderate pyelocaliectasis is not a sensitive sign of VUR, nor in differentiating early PUJ obstruction from the normal variant that subsequently resolves. Follow up ultrasound may confirm resolution or increasing hydronephrosis. Nuclear medicine studies will compare function and drainage of the systems in patients with PUJ obstruction.