An flush syringe assembly comprising: a barrel including a cylindrical side wall having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end including a distal wall with an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber; a plunger including an elongate body portion extending outwardly from said open proximal end of said barrel, said elongate body portion having a proximal end, a distal end having a discontinuity, a resilient stopper slidably positioned in fluid-tight engagement with said inside surface of said barrel for drawing fluid into and driving fluid out of said chamber by movement of said stopper relative to said barrel, characterized in that said stopper including a distal end having a distal surface and a proximal end having a cavity therein defining an inside surface having a first discontinuity and a second discontinuity located distally from said first discontinuity, said distal end of said plunger connected to said stopper by a complementary detent structure defining a first detent position wherein said plunger discontinuity engages said first discontinuity and a second detent position wherein said plunger discontinuity engages said second discontinuity, said detent structure being configured so that a distally directed force applied to said plunger after fluid has been delivered from said chamber causes said plunger to move distally with respect to said stopper from said first detent position to said second detent position so that a distal tip on said distal end of said plunger contacts said inside surface of said stopper forcing part of said distal end of said stopper into said passageway to move fluid distally in said passageway after fluid has been delivered from said chamber and said stopper is in contact with said distal wall. a barrel including a cylindrical side wall having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end including a distal wall with an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber; a plunger including an elongate body portion extending outwardly from said open proximal end of said barrel, said elongate body portion having a proximal end, a distal end having a discontinuity, a resilient stopper slidably positioned in fluid-tight engagement with said inside surface of said barrel for drawing fluid into and driving fluid out of said chamber by movement of said stopper relative to said barrel, characterized in that said stopper including a distal end having a distal surface and a proximal end having a cavity therein defining an inside surface having a first discontinuity and a second discontinuity located distally from said first discontinuity, said distal end of said plunger connected to said stopper by a complementary detent structure defining a first detent position wherein said plunger discontinuity engages said first discontinuity and a second detent position wherein said plunger discontinuity engages said second discontinuity, said detent structure being configured so that a distally directed force applied to said plunger after fluid has been delivered from said chamber causes said plunger to move distally with respect to said stopper from said first detent position to said second detent position so that a distal tip on said distal end of said plunger contacts said inside surface of said stopper forcing part of said distal end of said stopper into said passageway to move fluid distally in said passageway after fluid has been delivered from said chamber and said stopper is in contact with said distal wall.