| abstract |
To provide a centesis instrument capable of preventing a collapse or a swell from occurring on an outer needle when punctured and having less centesis resistance. [MEANS FOR SOLVING PROBLEMS] This centesis instrument (1) comprises the hollow outer needle (2), an outer needle hub (3) formed at the base end part of the outer needle, a hollow inner needle (4) inserted in the outer needle (2) for use, and an inner needle hub (5) formed at the base end part of the inner needle. The inner needle (4) comprises, starting at its tip side, a sharp needlepoint (41), a small diameter part (42) with an approximately constant outer diameter, an intermediate part (43) formed of a tapered part having an outer diameter gradually increasing toward the base end, and a large diameter part (44) having inner and outer diameters larger than those of the small diameter part (42). In the assembled state of the centesis instrument (1), the needlepoint (41) is mostly projected from the tip opening (24) of the outer needle (2), and the base end of the small diameter part (42) and the tip of the large diameter part (4) are positioned on the inside of the outer needle (2). Also, the inner diameter of the outer needle (2) at a portion L1 covering the small diameter part (42) of the inner needle (4) is smaller than the outer diameter of the large diameter part (44) of the inner needle (4). |