Epidemiologic characteristics of kidney malformations

Infants with kidney agenesis or dysgenesis, infants with cystic kidneys, an d infants with horse-shoe kidneys were studied, based on data from three la rge and population-based congenital malformation registers: a total of 2666 infants among 5.83 million births. There is a strong variability between p rograms of the rates of registered unilateral kidney malformations and thes e are strongly over-represented in dead infants or infants with other malfo rmations. There is a male excess but this varies in strength between differ ent types of kidney malformations and between bilateral and unilateral form s. An increased twinning rate was found. The different types of kidney malf ormation differed with respect to kind of associated non-urological malform ations in multi-malformed infants. We conclude that for monitoring purposes one should restrict analysis to bilateral forms but that unilateral forms can be of interest in epidemiological analyses.