A method and apparatus for cleansing the interior surfaces of body cavities employs a balloon catheter adopted to be inserted into a cavity through its ostium with the balloon in collapsed condition. An input flow tube for a cleansing and/or medicating fluid passes through a central passage in the balloon. When the balloon is inflated to establish a narrow passage between the balloon and the cavity walls, a pressurized flow of the fluid is pumped out the distal end of the input flow tube through the passage, parallel to the cavity walls, where it scours the inner wall of the cavity, removing debris as it flows out of the ostium. The fluid flow is urged toward a turbulent condition by attachments to the outer wall of the balloon.