Patent ID: 8562601

Claim:
A medical instrument for an endoscope to be used in the endoscope by being inserted therein, comprising: a flexible elongated sheath having a first lumen and a second lumen; a conductive wire which is inserted into the first lumen and of which a portion of a distal side is exposed to the outside of the sheath as a treatment unit; and a balloon which is attached to the sheath, is expandable with a supply of fluid from the second lumen, and is in close contact with the outer circumference of the sheath and an outer diameter of the balloon is equal to or less than an outer diameter of the sheath that is proximal to said balloon in an initial state of the balloon, and the outer diameter of the balloon is substantially constant in an axial direction, wherein the balloon is configured such that an axial dimension thereof is larger than a radial dimension upon expansion and a distal end of the balloon upon expansion is located closer to a proximal side of the sheath than the treatment unit exposed from the sheath.