Renal Agenesis Surveillance -- United States

Based on data from the Birth Defects Monitoring Program (BDMP)*, since 1970, the reported prevalence of kidney defects coded under the International Classification of Diseases (ICD) code 753.0 has increased threefold in the United States (Figure 1). To determine whether this reflected a true increase or resulted from a change in detection or reporting practices, CDC evaluated information about cases from 590 (88%) of 674 hospitals reporting to the BDMP at least one newborn with a kidney defect coded as 753.0 from 1970 through 1983. During 1970-1978, this code was classified only as renal agenesis--the congenital absence of one (unilateral) or both (bilateral) kidneys--and during 1979-1983, as renal agenesis and dysgenesis (abnormal kidney formation). This evaluation showed that the increase in reported cases of renal agenesis actually reflected changes in reporting of other renal anomalies. These findings have implications for surveillance of birth defects and suggest that differences may exist between actual clinical diagnoses and the coding of these medical conditions.

Newborns with bilateral renal agenesis have low-set, floppy ears, a broad, flat nose, and underdeveloped lungs. These newborns often die of respiratory failure within a few hours of birth. Lungs of infants with at least one functional kidney usually develop normally; thus, unilateral renal agenesis is often not detected during the perinatal period.

The cases in this evaluation included 1404 newborns with an ICD code of 753.0. Participating hospitals provided copies of the discharge summary, pathology reports, and x-ray reports. For 966 (69%) of the infants, hospital reports supported the diagnosis of renal agenesis or renal dysgenesis. Of these, 468 (48%) had bilateral renal agenesis, 105 (11%) had one agenic and one dysgenic kidney, 229 (24%) had bilateral renal dysgenesis, 136 (14%) had unilateral renal agenesis, and 28 (3%) had unilateral renal dysgenesis.

For the 14-year period 1970-1983, clinical reports of anomalies coded to 753.0 showed the following trends: 1) the annual frequency of bilateral renal agenesis varied considerably but appeared to increase slowly; 2) the prevalence at birth of one agenic and one dysgenic kidney remained constant; 3) the annual frequency of unilateral renal agenesis varied, although the number of infants with this diagnosis was small, and most cases were found incidentally during autopsy; and 4) the incidence of bilateral renal dysgenesis increased 10-fold from 0.03 per 10,000 births in 1970 to 0.33 per 10,000 births in 1983.

These findings suggest that the reported increase in kidney anomalies coded as 753.0 was not due primarily to increased incidence in renal agenesis but to increases in other renal anomalies, including renal dysgenesis. Because renal dysgenesis was not specifically listed under ICD code 753.0 before 1980, it may have been coded under cystic kidney disease (ICD 753.1). Consequently, to determine whether coding practice alone might account for the increase in renal dysgenesis, statistical data for cystic kidney disease were also examined. This examination revealed that before 1980, the reported prevalence of cystic kidney disease (753.1) was decreasing, while the reported prevalence of renal agenesis (753.0) increased. In addition, during 1980-1983, prevalence rates for both cystic kidney disease (753.1) and renal agenesis and dysgenesis (753.0) increased. Data from the BDMP surveillance system also suggest that since 1980, the prevalence of congenital ureteral obstruction, a condition often associated with polycystic kidneys, has increased. Hence, the apparent increase in renal dysgenesis appears to be independent of changes in ICD revisions and coding practices.

Although data on birth defects from the MDHIS are available only since 1982, prevalence rates of renal agenesis reported through this system from 1982 through 1987 have increased slightly (Figure 2). For this same time period, average annual prevalence of reported cases of renal agenesis per 10,000 births was similar for both BDMP components: CPHA (1.9) and MDHIS (1.6). Stillbirths in the CPHA data partly account for the slightly higher rate reported by this system. Reported by: Birth Defects and Genetic Diseases Br, Div of Birth Defects and Developmental Disabilities, Center for Environmental Health and Injury Control, CDC.

Editorial Note

Editorial Note: The BDMP provides medical information on about 1.3 million newborns per year, or 35% of U.S. births. Hospital discharge abstracts on these newborns are coded by hospital medical records personnel and submitted regularly to CPHA or MDHIS for processing. The major difference between the two systems is that stillbirths are included in the CPHA data but not in the MDHIS data.

CDC analyzes 161 birth defect categories to identify unusual trends and geographic differences within the CPHA and MDHIS data (1). Defects are usually reported 3-6 months after an affected infant's birth, and the data are reviewed four times a year. Although these data sources are not population-based and are not a random sample of U.S. births, they nevertheless represent the largest single set of uniformly collected and coded discharge data on birth defects among newborns in the United States.

The number of cases of renal agenesis confirmed by clinical data appears to be relatively constant. However, the prevalence of a variety of other renal anomalies, including renal dysgenesis, although still rare, appears to be increasing. Renal anomalies, however, often occur along with other anomalies of the genital tract. Since renal dysgenesis may be a sentinel event, then an increase in this birth defect suggests that other, less severe genitourinary anomalies also may be increasing.

The BDMP will continue to monitor reports of renal agenesis and dysgenesis as well as other birth defects to detect changes in the prevalence of anomalies by geographic area. This monitoring will aid in identifying and eliminating causes of congenital malformations.

Reference

1. CDC. Congenital malformations surveillance, January 1982-December 1985. Atlanta: US Department of Health and Human Services, Public Health Service, March 1988. *The BDMP, initiated by CDC in 1974, is a surveillance system for monitoring birth defects in newborns. The system comprises two data bases: the Commission on Professional and Hospital Activities (CPHA), which contains data since 1970, and the McDonnell Douglas Health Information System (MDHIS), which has data available since 1982.

Disclaimer   All MMWR HTML documents published before January 1993 are electronic conversions from ASCII text into HTML. This conversion may have resulted in character translation or format errors in the HTML version. Users should not rely on this HTML document, but are referred to the original MMWR paper copy for the official text, figures, and tables. An original paper copy of this issue can be obtained from the Superintendent of Documents, U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800. Contact GPO for current prices.

Page converted: 08/05/98

HOME  |  ABOUT MMWR  |  MMWR SEARCH  |  DOWNLOADS  |  RSS |  CONTACT POLICY  |  DISCLAIMER  |  ACCESSIBILITY

Morbidity and Mortality Weekly Report Centers for Disease Control and Prevention 1600 Clifton Rd, MailStop E-90, Atlanta, GA 30333, U.S.A Department of Health and Human Services

This page last reviewed 5/2/01