An endoscopic instrument, particularly a continuous flushing cysto-urethroscope, has an oval cross-sectioned outer shaft and an inner shaft having a contour formed by two semi-circular arcs with different diameters, the arcs having their openings facing each other and connected by two approximately straight...http://www.google.ca/patents/US5509892?utm_source=gb-gplus-sharePatent US5509892 - Endoscopic instrument
