Purpose: Congenital solitary kidney affects 1 in 1000 persons, whereas bilateral renal agenesis affects 1 in 5000. Because congenital solitary kidney is increased in parents of infants with bilateral renal agenesis and fetuses with renal anomalies on ultrasound, offspring of patients with congenital solitary kidney may be at risk of both unilateral and bilateral renal anomalies. The goal was to establish empiric risk estimates for counseling individuals with congenital solitary kidney.
Methods: Through a computerized review of records, subjects with congenital solitary kidney (defined as presumably congenital absence or severely reduced function of one kidney) were identified and asked to complete a questionnaire regarding urogenital anomalies in relatives.
Results: Empiric risks of 7% for offspring, 4% for parents, and 2.5% for siblings are minimal because not all relatives underwent ultrasound studies. The incidence of bilateral renal agenesis in offspring of congenital solitary kidney probands is 0.8%, which is much greater than the population risk but less than that for families with previous bilateral renal agenesis. Concordance for type of anomaly in affected relatives is only 50%, suggesting that various anomalies included in congenital solitary kidney (agenesis, dysplasia, cystic dysplasia) may overlap. Horseshoe kidney has 80% concordance and may be a separate autosomal dominant condition.
Conclusion: Offspring and other relatives of individuals with congenital solitary kidney have significantly increased renal disease. Ultrasound is recommended for first-degree relatives, including fetuses at risk.