Abstract: Disposable gynecologic instrument for dilation of body cavities by fluid injection, the construction according to the invention, include the instrument body (1) to which it has from the bottom tightly fixed a handle (2) with the reservoir (3) whilst is on the frontal part of the instrument body (1) projected is the trigger (4) positioned slidingly and designed for pressing with two fingers, which is by screw (41) connected to the main piston (42) movable within the cylinder, around which is placed a bigger spring (43) and where the outlet of cylinder is connected to one branch of the three-way pipeline (44), the other two of which are connected, one on the upper irreversible valve (12), and the other to the lower irreversible valve (22); and where is also on the front side of the instrument body (1) by screw thread and sealingly attached the main pipe (5), formed with longitudinal ribs (51) positioned crosswise and a series of aslope placed ribs (52) of circular perimeter, which increase the stiffness of the