An endoscope includes a shaft having proximal and distal ends and a longitudinal axis therebetween. A handle is coupled to the proximal end of the shaft, and an image sensor is carried on the distal end of the shaft. A channel extends through at least a distal shaft portion and has a channel diameter, and a section of the channel is re-configurable between a constricted shape and a non-constricted shape to accommodate tools introduced therethrough. The combined diagonal dimension and channel diameter is usually greater than the outer shaft diameter. The image sensor may be connected to a connector on the housing by a first slack flex circuit and a lights source on the shaft may be connected to a connector on the housing by a second slack flex circuit.