1. From the Department of Nephrology, Kidney Transplantation and Hypertension (L.O., M.L.), The Children’s Memorial Health Institute, Warsaw, Poland
2. Division of Nephrology, Department of Pediatrics, The Children’s Hospital of Eastern Ontario, Ottawa, Canada (J.F.)
3. Outpatient Clinic, “Esculap,” Gniewkowo, Poland (T.D., W.L.).
4. Department of Public Health (Z.K.), The Children`s Memorial Health Institute, Warsaw, Poland