A comparison of outcomes of urinary tract abnormalities detected by the routine second and a routine third trimester ultrasound scan.

OBJECTIVES

Urological abnormalities are commonly detected on antenatal ultrasound scanning, representing 1% of all fetal abnormalities and traditionally detected by the routine second trimester (T2) scan. The implementation of a routine third trimester (T3) scan for the diagnosis of small-for-gestational age fetuses has concurrently diagnosed a spectrum of new antenatal abnormalities. The purpose of this study was to compare the incidence and patient outcomes of urological abnormalities diagnosed at the T2 vs. those at the T3 scan.

STUDY DESIGN

A retrospective search of our institutional database of 8,554 patients who underwent T2 and T3 scans in a tertiary-level Fetal Medicine Unit. We found results for all routine scans with commentary about renal or urinary tract abnormalities in singleton pregnancies. We collected maternal demographics, antenatal diagnoses and the results of any follow-up scans. Neonatal demographics and definitive diagnosis at birth were collected and subsequent management by paediatric urologists. SPSS software was used for statistical significance testing between the groups. Sensitivity and Specificity analysis was also carried out for both scans.

RESULTS

76 urinary tract abnormalities were detected in the T2 cohort compared to 26 at the T3 scan. The incidence of true renal abnormalities diagnosed by the T2 scan was 0.55 %, and 0.21 % vs. T3 scan. Postnatally, there were 47 confirmed abnormalities in the T2 group compared to 18 in the T3 group (p > 0.05). Common findings included hydronephrosis, duplex kidney, renal agenesis, multicystic kidneys, and pelvic kidney. There were no significant differences in numbers needing antibiotics (n = 32, n = 13, p = 1.00), urinary tract infections (n = 5, n = 1, p = 1.00) and surgical procedures (n = 17, n = 4, p = 0.379) in the T2 and T3 group respectively.

CONCLUSION

We found no significant difference in the types, severity, and outcome of renal abnormalities between the two groups. This highlights the importance of the T2 scan but brings into discussion the utility of the T3 scan at identifying a number of additional urinary tract anomalies that would otherwise be missed on T2 scanning that ultimately required surgical management.