A medical instrument comprises a guide tube (10) that can be inserted into a bodily passage of a patient. An elastically flexible cannula may be displaced within an inner axial guide channel of the guide tube (10), the distal tip (52) of the cannula being able to emerge from a lateral opening at the periphery of the guide tube (10) at an angle to the axis of the guide tube (10). The guide tube (10) at its proximal end is accommodated in a handle piece (22) so as to be rotatable about the longitudinal axis of the guide tube.