Objective: We investigated the sonographic measurements of the functioning kidney of children who were born with a single functioning kidney.
Materials and methods: In 56 children (0-6 years old) with one multicystic dysplastic kidney and one functioning kidney, the length of the functioning kidney was correlated with the child's age, weight, and body surface area.
Results: The mean length of the kidney was 51.0 mm in children 2 weeks old, 56.8 mm at 9 weeks, 62.8 mm at 23 weeks, 69.6 mm at 46 weeks, 71.7 mm at 63 weeks, 78.0 mm at 112 weeks, 79.6 mm at 172 weeks, 86.7 mm at 225 weeks, and 91.0 mm at 279 weeks. When these results were compared with existing sonographic standards for bilateral functioning kidneys, the single functioning kidneys were longer by a statistically significant amount.
Conclusion: Compensatory hypertrophy of single functioning kidneys occurs in utero. In children of the ages we investigated, the size of single functioning kidneys exceeded established standards for the size of bilateral functioning kidneys.