A non-sterile endoscopic sheath with two inflatable balloons designed to be mounted on a colonoscope to position and stabilize the endoscope within the large intestine of a patient. It is made of synthetic polymer materials and is in the form of a tubular shaft with a manually-controlled proximal handle used to inflate/deflate the two distal balloons, which upon inflation create an isolated diagnostic or therapeutic zone in the target region. This is a single-use device.