A user friendly, safe and efficient continuous flow irrigation endoscope having only a single housing sheath without an inner sheath. The exclusion of the inner sheath increases the effective lumen of the endoscope. A long hollow cylindrical tube, capable of performing a to and fro and rotary motion, is placed inside the housing sheath to function as an endoscopic instrument, but also to serve as a conduit for evacuating waste fluid and detached tissue pieces present inside a tissue cavity. A single inflow port located at the proximal end of the single housing sheath allows the irrigation fluid to enter the tissue cavity via the lumen of the said housing sheath. The invented endoscope system has a single inflow port, a single outflow port, without an inner sheath so that all waste fluid and tissue debris present inside cavity are evacuated via the same single outflow port. No type of feedback mechanism, such as mechanical or electrical feedback mechanism, is incorporated in the endoscope to facilitate the removal of detached tissue pieces or waste fluid.