Fetal pyelectasis: comparison of postnatal renal pathology with unilateral and bilateral pyelectasis

The aim of this study was to determine the prenatal fetal pyelectasis which requires postnatal evaluation. This was a retrospective analysis involving 65 infants with complete urological follow-up; 59 had shown prenatal evidence of pyelectasis using previously published standards. Males were more common in both the normal (75 per cent) and the abnormal (77 per cent) postnatal outcome groups. Unilateral prenatal lesions were less common than bilateral, but had significant postnatal pathology in 47 and 26 per cent, respectively (n.s.). Persistent dilatation was likely to be associated with postnatal pathology. A 6 mm threshold of dilatation predicted the 19 infants with significant postnatal pathology. The majority of fetuses with pyelectasis in the study had normal outcomes, with males often showing 'transitory pyelectasis'. A repeat prenatal scan at 30-40 weeks' gestation is recommended for all fetuses where 6 mm or more of renal pelvic dilatation is detected prior to 28 weeks. Postnatal follow-up is required for persistent pyelectasis.