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INTRODUCTION
In the United Kingdom, the diagnosis of fetal uropathy is based on the screening second-trimester sonographic assessment, performed between 18 and 22 weeks of gestation. Recently some fetal medicine units have added a screening third-trimester scan, intended initially to assess fetal growth towards the end of pregnancy. This has also provided a thorough review of fetal anatomy at this gestation and resulted in the diagnosis of many new uropathies. We report on the impact of this screening third-trimester scan in giving us a new population of patients to evaluate and treat postnatally and review the resulting diagnoses made.
METHODS
Between 1st April 2012 and 1st December 2014, 8,554 consecutive pregnancies were screened with both a second and third-trimester antenatal scan. All patients diagnosed with a fetal uropathy in either of these scans were identified from the fetal medicine database. Prenatal findings and post-natal follow-up and evaluation were reviewed from the medical records and imaging files of the mother and baby. The incidence of uropathies found at both scans was evaluated and follow-up information was collated for those diagnosed exclusively during the third trimester.
RESULTS
67 fetuses were found to have renal and urologic anomalies on their second-trimester scan, an incidence of 0.8% of all pregnancies. In 14 of these cases (21%) the dilatation was transient and resolved in subsequent antenatal scans.
34 fetuses with a normal second-trimester scan were diagnosed with a urological abnormality from the screening third-trimester scan only. Follow-up information was available in 31 of these babies of which 15 were male and 16 were female. Postnatal evaluation by paediatric urologists revealed 14 cases of hydronephrosis (3 bilateral), 5 patients were found to have vesico-ureteric reflux (3 bilateral), 1 posterior-urethral valves, 1 unilateral megaureter, 1 duplex kidney, 1 megaureter, 1 pelvi-ureteric junction stenosis, and 2 unilateral renal agenesis. 5 patients either resolved their sonographic appearances or had normal postnatal ultrasound scans (16%). Postnatally, 14 received antibiotic prophylaxis as their only intervention, whilst 6 required surgery. This included Deflux© injections, posterior urethral valve ablation, circumcision, and pyeloplasty. The incidence of new third-trimester uropathy was 0.4% in our series giving an overall incidence of uropathy of 1.2%.
DISCUSSION
Increasing urine flow in late gestation may explain the large numbers of uropathies found for the first time by the screening third trimester scan. Hydronephrosis is transient in similar numbers to those diagnosed earlier and likewise, there are similar rates of surgical intervention postnatally. Adoption of the third-trimester scan as routine screening has increased the prenatal population for evaluation by 50%. There is the potential for over-investigation and over-treatment of some patients that might remain well undetected. However, it is concerning that some important diagnoses requiring operative intervention are missed by earlier scans. Undoubtedly many patients found by the screening third-trimester scan would otherwise present clinically later in life and will have been saved the morbidity of an acute episode.