Unilateral renal agenesis diagnosed on early prenatal transvaginal scans

Background: Unilateral renal agenesis is a rare finding. There are no large-scale studies reporting this finding in early pregnancy. Objectives: To evaluate the incidence of unilateral renal agenesis (URA) and of associated anomalies diagnosed by early prenatal transvaginal sonography. Methods: We performed a retrospective chart review of all 59,382 transvaginal scans performed at 14-16 weeks gestation by a single operator at different clinics during the period 1994-2013. Results: The incidence of URA was 1:1212 (49/59382 cases). Associated anomalies were diagnosed in 22 cases (45%). Renal anomalies were diagnosed in 22.4%. Extra-renal anomalies (with exclusion of a single umbilical artery or nuchal edema as isolated findings) were diagnosed in 24.5%. Ambiguous genitalia were diagnosed in 8.2%. Conclusions: URA is a rare finding in early transvaginal sonography. Associated anomalies are common and should be sought.