Renal agenesis and dysgenesis: are they increasing?

Data from the Birth Defects Monitoring Program (BDMP) of the Centers for Disease Control (CDC) suggest that the birth prevalence of renal agenesis and dysgenesis combined is increasing. Medical records were reviewed for 1,404 of 1,669 (84%) infants in the BDMP with renal agenesis or dysgenesis noted on the newborn discharge summary to assess whether the observed trend reflects a true increase in one or both conditions or if it reflects changes in diagnostic, coding, or surveillance practices over time. For 1970-1982, the average rate per 100,000 live births and stillbirths was 3.5 for autopsy-confirmed bilateral renal agenesis and 1.7 for autopsy-confirmed bilateral renal dysgenesis. The birth prevalence of autopsy-confirmed bilateral renal agenesis fluctuated within this time period, peaking in 1975, while the rate of autopsy-confirmed bilateral renal dysgenesis increased steadily by 0.2 cases/100,000 births per year (P less than 0.001) with small peaks in 1976 and 1979. Unilateral renal agenesis or dysgenesis accounted for 17% of the confirmed cases, but most were detected by autopsy among infants who died shortly after birth rather than by diagnostic procedures such as ultrasound. Diagnostic information in the medical record suggested that the increase in the birth prevalence of renal agenesis and dysgenesis combined in the BDMF is due primary to the increasing prevalence of renal dysgenesis. Since medical records did not include sufficient information on risk factors, detailed analytic studies are needed to identify maternal risk factors that might account for the apparent increase in renal dysgenesis over time.