Endoluminal treatment method and associated surgical assembly including tissue occlusion device

A system for endoscopic surgery within a body lumen of a patient comprising a body member having a distal portion expandable from a collapsed insertion configuration to an expanded configuration to provide an expanded chamber having an expanded region therewithin having an increased transverse dimension proximal of a distalmost end of the body member, the chamber having an opening to receive tissue into the chamber and the chamber expandable asymmetrically, an elongated working channel in the body member dimensioned to receive a working instrument therethrough such that a working head of the instrument is angled laterally into within the expanded region of the chamber and positionable within the chamber to access the tissue received within the chamber, the elongated working channel having a first opening into the chamber to enable the working head of the working instrument to access the chamber and a second channel dimensioned to receive a visualization device to visualize tissue within the chamber, the first channel positioned radially of the received visualization device in the second channel such that the working instrument received in the first channel is movable independently of the visualization device received in the second channel, the second channel having a second opening into the chamber separate from the first opening to access the chamber for visualization separate from insertion of the working instrument.