Screening for fetal urological abnormalities: how effective?

Objective To analyse urological cases registered with the Northern Congenit al Abnormality Survey (NorCAS) and thus assess antenatal diagnostic sensiti vity, measure regional interhospital variation and determine whether antena tal ultrasonography has contributed to the prevention of urinary tract dise ase in childhood. Methods All notification documents forwarded to NorCAS from its inception i n 1984 until 31 December 1996 were inspected and those relating to urologic al abnormalities were abstracted, Information about postnatal progress was often missing. Twenty-three hospitals delivering maternity services were id entified and randomly allocated a code letter a-w. Data were analysed in tw o periods, 1984-90 and 1991-96, To quantify hospital performance an 'expect ed number for each hospital was calculated from the overall incidence per 1 000 births and the number of births in each hospital, Results There was a clear improvement in antenatal diagnostic sensitivity f or the major urological abnormalities in the second period, but there was c onsiderable variation among hospitals in the number of cases notified: this applied particularly to antenatal renal dilatation. Two hospitals notified significantly more cases in this category than all the others. The differe nce in notification rates among hospitals was caused by diagnoses such as v esico-ureteric reflux (VUR), pelvi-ureteric junction obstruction and megaur eter, which often produce antenatal renal dilatation, Hospitals which notif ied more of these cases performed more micturating cystograms and identifie d more children with VUR. Measurements of the fetal renal pelvis were regul arly made by only seven hospitals; one of these had difficulties with postn atal follow-up. There was evidence that moderate degrees of antenatal renal dilatation (4-10 mm) were associated with VUR, 8.5% of the children in who m VUR was diagnosed had fetal renal dilatation of this order. Conclusion Antenatal renal dilatation and its significance are either not b eing recognized or not appreciated in some hospitals. The high incidence of VUR in cases with moderate antenatal renal dilatation indicates that child ren with this condition may be escaping diagnosis.