A 13-year-old's kidney was failing. Then a stranger stepped in.

When Elias Manolis started experiencing extreme fatigue early last year, his parents were alarmed, but not surprised. The 13-year-old from Long Island, New York, had been born with ureterovesical junction obstruction, a rare congenital disease, where a blockage between the ureter and bladder causes urine to back up into the kidney. The condition can cause pain, infections and fevers. …