Medical device insertion method

A medical device insertion method for inserting an overtube and an endoscope into the large intestine, the overtube comprising a reinforced region in at least one part in a longitudinal axis direction, the reinforced region including a wire disposed in at least one part of an outer circumference of the overtube and disposed along the longitudinal axis direction, the method comprising:

• inserting the endoscope into the overtube until a distal end of the endoscope is positioned to protrude from a distal end of the overtube;
• grasping a part of the endoscope protruding from the distal end of the overtube and inserting the endoscope into the large intestine until the distal end of the endoscope is positioned between the splenic flexure and the sigmoid colon of the large intestine;
• and
• subsequent to the grasping, inserting the overtube together with the endoscope into the large intestine until the distal end of the endoscope is placed beyond the splenic flexure while grasping the overtube from an outer radial direction so as to deform the overtube in an inner radial direction until an inner surface of the overtube is pressed against an outer circumferential surface of the endoscope.