Methods and systems for performing submucosal medical procedures

A method of forming a submucosal tunnel comprising the steps of:

• elevating a mucosal layer at a target site by injecting a fluid into a submucosal layer beneath the mucosal layer using a needle assembly to form an elevated bleb;
• inserting a submucosal tunneling instrument through a natural orifice into the digestive tract of a mammal, said submucosal tunneling instrument comprising an elongate tubular member having proximal and distal ends and a lumen extending therethrough and an expandable member having proximal and distal ends wherein the proximal end of said expandable member is attached to the distal end of said tubular member and the distal end of said expandable member is everted and positioned within the lumen of said tubular member;
• inserting said submucosal tunneling instrument into the elevated bleb beneath said mucosal layer;
• and
• operating said submucosal tunneling instrument to create an elongate tunnel in the submucosal layer, said operating includes expanding said expandable member substantially greater in length than in diameter to form a narrow space in the submucosal layer.