This invention relates generally to an endoscope accessory. This device uses an overtube with an inflatable positioning ring that can be inflated after placement of the overtube just proximal to the tip of the endoscope or echoendoscope. A catheter with an occlusion balloon at its free endportion is carried by the overtube and extends beyond the tip of the endoscope, distal to the part of the body cavity that needs to be examined. Inflation of this balloon together with positioning ring creates a closed space within the body cavity that can be filled with air or water for improving the quality of the examination with regular endoscope of echoendoscope, respectively, while reducing the examination complications.