The following secondary outcome measures were not significantly different between the 1W and the 4W series with regard to residual symptoms ( 10 vs 6 % ; P = 0.48 ) , rate of complications ( 4 vs 6 % ; P = 0.65 ) , need for synchronous robot-assisted pyelolithotomy ( 4 vs 8 % ; P = 0.47 ) , improvement in split renal function ( 1 vs 0 % ; P = 0.59 ) and duration of surgery ( 200 vs 192min ; P = 0.87 ) .