An instrument for accessing and visualizing hollow organs is provided. The instrument includes a mouthpiece having a perforated mask and a sleeve having a generally cylindrical or ovoid shape extending from the perforated mask substantially perpendicularly thereto and defining a channel. The instrument further includes sucking means having a suction chamber or closed volume that is restrained to the mask on the side where the sleeve is formed. The suction chamber has a plurality of through openings adapted to allow fluid communication with a surrounding environment, an intake opening communicating with the suction chamber formed on the mask, wherein the through openings are formed on the skirt of a dome-shaped member which delimits the suction chamber.