Endoscopic system, over-tube, and cap

A cap being mounted on a distal end of an over-tube that includes a tubular member having a treatment tool channel into which a treatment tool can be inserted and an endoscope channel into which an endoscope can be inserted, the cap comprising:

• a treatment tool exit hole disposed at a position that is held in fluid communication with the treatment tool channel;
• an endoscope exit hole disposed at a position that is held in fluid communication with the endoscope channel;
• and
• a protrusion configured to protrude radially inwardly from an inner circumferential surface of the endoscope exit hole and configured to indicate a circumferential position of the treatment tool exit hole with respect to the endoscope exit hole.

An endoscopic system comprising:

• an elongated over-tube having at least one treatment tool channel and an endoscope channel spaced apart from one another and being longitudinally formed therein, respectively;
• at least one treatment tool configured to be inserted into the treatment tool channel;
• and
• an endoscope configured to be inserted into the endoscope channel wherein the endoscope channel includes a protrusion formed in a vicinity of a distal end of the endoscope channel in a longitudinal direction and being configured to indicate a position in a circumferential direction of the treatment tool channel with respect to the endoscope channel.