Over-tube, method of manufacturing over-tube, method of disposing over-tube, and method of treatment in abdominal cavity

An over-tube which is used in combination with an endoscope having an elongated insertion section, comprising:

• an over-tube main body having a distal portion on one end of an elongated tube and a proximal portion on the other end thereof and being capable of passing the insertion section of the endoscope, the over-tube main body being inserted from the distal portion thereof into a patient's body through a natural opening to access an abdominal cavity through a lumen wall from the distal portion thereof;
• and
• at least one internal cover which has a tubular shape and through which the insertion section of the endoscope is inserted in a detachably inserted state in an inner cavity of the over-tube main body, the internal cover having a distal portion which is disposed in a protruded state further on a front side from the distal portion of the over-tube main body and which covers an outer peripheral surface of the distal portion of the over-tube main body, and a proximal portion protruded on a hand side from the proximal portion of the over-tube main body, so that the internal cover is extractible from the proximal portion of the over-tube main body;
• wherein the over-tube main body includes a detachable portion to which the distal portion of the internal cover is detachably attached on an outer peripheral surface;
• and
• when detaching the internal cover with respect to the over-tube main body, a state which the distal portion of the internal cover is attached on the detachable portion of the over-tube main body is released, and the distal portion of the internal cover is extractable from the proximal portion of the over-tube main body through the distal portion and the inner cavity thereof.