Apparatus comprising: a sleeve adapted to be slid over the exterior of an endoscope; an aft balloon secured to the sleeve; an inflation/deflation tube carried by the sleeve and in fluid communication with the interior of the aft balloon; a pair of hollow push tubes slidably mounted to the sleeve, the pair of hollow push tubes being connected to one another at their distal ends with a raised push tube bridge, the raised push tube bridge being configured to nest an endoscope therein; and a fore balloon secured to the distal ends of the pair of hollow push tubes, the interior of the fore balloon being in fluid communication with the interiors of the pair of hollow push tubes, wherein the fore balloon is capable of assuming a deflated condition and an inflated condition, and further wherein (i) when the fore balloon is in its deflated condition, an axial opening extends therethrough, the axial opening being sized to receive the endoscope therein, and (ii) when the fore balloon is in its inflated condition, the axial opening is closed down.