FAMILY STUDY OF RENAL AGENESIS

A family study of bilateral renal agenesis was undertaken based on 103 patients with bilateral renal agenesis, ascertained through stillbirth and neonatal death certificates, and confirmed by necropsy reports; 28 were ascertained through paediatric pathologists. The families of 108 of these were traced and visited. The birth frequency in the year in which ascertainment was likely to be most complete, 1974, was estimated to be 0.12 per 1000 total births, but it is recognised that this will be an underestimate. No significant variation was found by geographical region, parental birth place, socioeconomic class, maternal age, or birth order. There was, however, an excess of conceptions in the spring quarter (March, April, and May), similar to, but in this series more marked than, that seen in neural tube malformations. The proportion of sibs affected was 7 in 199 (3.5%); of these, 6 were bilaterally and 1 was unilaterally (with an enlarged contralateral cystic kidney) affected. This is rather too high to be explained by multifactorial inheritance unless the estimate of the birth frequency is much too low. The proportion of sibs affected was similar for index patients with 'single' bilateral renal agenesis, with only embryologically related malformations, and for index patients with associated malformations of unrelated bodily systems. Of the 199 sibs, 5 had neural tube malformations, but in 3 of these instances the index patient also had a neural tube malformation as well as renal agenesis. Where the index patient had ureteric remnants, 1 in 12 sibs were affected, but this high proportion may well just be a chance effect. Coincidence within families suggests that unilateral renal agenesis is genetically related to bilateral renal agenesis, and that cases of bilateral renal agenesis without ureters are not genetically different from those with ureteric remnants.