Dilator

A dilator comprising:

• a hollow-shaped shaft comprising (i) a tapered section with an outer diameter of a distal end being smaller than an outer diameter of a proximal end, (ii) a distal end section including a proximal end being located at the distal end of the tapered section and extending toward a distal end side of the tapered section in an axial direction, and (iii) a body section including a distal end being located at the proximal end of the tapered section and extending toward a proximal end side of the tapered section in the axial direction;
• and
• a spirally-arranged protruding portion comprising (i) spirally-arranged protruding sections provided on outer peripheral surfaces of each of the tapered section, the distal end section, and the body section, and (ii) gaps between adjacent spirally-arranged protruding sections along the axial direction of the shaft,
• wherein a location being at a terminal distal end side of the spirally-arranged protruding portion and including a distal end of the spirally-arranged protruding portion is a first location and a location being at a proximal end side of the spirally-arranged protruding portion and at the proximal end side relative to the first location and including a proximal end of the spirally-arranged protruding portion is a second location,
• at least one of (i) a height of the spirally-arranged protruding portion at the first location gradually decreases toward the distal end side of the spirally-arranged protruding portion, and (ii) a height of the spirally-arranged protruding portion at the second location gradually decreases toward the proximal end side of the spirally-arranged protruding portion,
• the body section includes a straight part with a constant outer diameter, the straight part having a distal end located at the proximal end of the tapered section and extending toward a proximal end side of the body section in the axial direction,
• the spirally-arranged protruding portion extends continuously from the tapered section through to the straight part and a shape of an outer peripheral surface at at least one of the first location and the second location in the spirally-arranged protruding portion is a concave shape.

A dilator comprising:

• a hollow-shaped shaft formed of a coil body formed by winding a wire around an axis of the shaft, and comprising (i) a tapered section with an outer diameter of a distal end being smaller than an outer diameter of a proximal end, (ii) a distal end section including a proximal end being located at the distal end of the tapered section and extending toward a distal end side of the tapered section in an axial direction, and (iii) a body section including a distal end being located at the proximal end of the tapered section and extending toward a proximal end side of the tapered section in the axial direction;
• and
• a spirally-arranged protruding portion comprising (i) spirally-arranged protruding sections provided on outer peripheral surfaces of each of the tapered section, the distal end section, and the body section, and (ii) gaps between adjacent spirally-arranged protruding sections along the axial direction of the shaft,
• wherein a location being at a distal end side of the spirally-arranged protruding portion and including a distal end of the spirally-arranged protruding portion is a first location and a location being at a proximal end side of the spirally-arranged protruding portion and at the proximal end side relative to the first location and including a proximal end of the spirally-arranged protruding portion is a second location,
• the spirally-arranged protruding portion directly contacts the coil body, and
• at least one of (i) a height of the spirally-arranged protruding portion at the first location gradually decreases toward the distal end side of the spirally-arranged protruding portion, and (ii) a height of the spirally-arranged protruding portion at the second location gradually decreases toward the proximal end side of the spirally-arranged protruding portion.