An assembly of parts for an endourological procedure, comprising an elongate tubular sheath (1) and an elongate introducer (2), the tubular sheath being removably mounted on the introducer. The introducer comprises at least one security channel (61) being openable to shift a guidewire from a position inside the security channel to a position outside and next to the tubular sheath using a controllable ejecting means adapted to externalise the guidewire upon activation. The ejecting means can be an expandable or inflatable member (20). Disclosed are also access sheaths for an endourological procedure.
