A device and method are provided for flushing during endoscopic surgery to solve the problem of debris in the operating cavity. Included is the ability of reversing the inflow and outflow channels of the endoscope to make possible the beneficial cleaning of the ports of the endoscope from debris and e.g. bone particles without a need for removal of the optical instrument during such flushing procedure and consequently avoiding loss of pressure in the body cavity and spillage. Increased flushing occurs by providing a pressure-holding valve in the proximal opening of the double-channel endoscope, where the optical instrument is inserted, making it possible to remove the optical instrument and then enable the full channel of the endoscope sheath to be used for efficient evacuation of debris without loss of pressure in the operating cavity or spillage on the floor.
