Twenty-seven patients ( 37 % ; 95 % CI , 25.9 % -48.1 % ) in the sham treatment group vs 32 ( 23 % ; 95 % CI , 15.8 % -29.6 % ) in the sphincterotomy group experienced successful treatment ( adjusted risk difference , -15.6 % ; 95 % CI , -28.0 % to -3.3 % ; P = .01 ) .