A sheath assembly for different fields of endoscopic surgery involving suction, irrigation and material removal comprising a tubular sheath including a sheath cannula having an inner open end for introducing into body region requiring surgery and a suction unit with controllable suction provision operatively connected to the outer other open end of the tubular sheath comprising a reservoir. The reservoir includes a reservoir inlet connected in line with the outer other open end of the tubular sheath, a reservoir outlet connected to a suction machine and perpendicularly disposed with respect to the reservoir inlet, a releasably attachable sealing assembly to allow passage of operating endoscope through the reservoir and make assembly of the reservoir and the operating endoscope water and air tight for functioning of the suction unit; and a suction control opening disposed in operative cooperation with said reservoir outlet to provide alternative suction zone in the sheath assembly.