Procedures of bilateral intervention included: PCNL in 4.5%; retroperitoneoscopic ureterolithotomy in 18.2%; ureteroscopic lithotripsy in 40.9%; PCNL plus ureteroscopic lithotripsy in 13.6%; PCNL plus retroperitoneoscopic ureterolithotomy in 13.6% and retroperitoneoscopic ureterolithotomy plus ureteroscopic lithotripsy in 9.1%.