Endoscopes include a shaft having a diameter extending about a longitudinal axis to a distal housing. An image sensor is carried by the distal housing, and a channel extends through the shaft and distal housing. A distal portion of the channel is adjustable or curved to accommodate introduction of a tool while maintaining a reduced shaft diameter. In some embodiments, a diagonal dimension of the image sensor when combined with a channel diameter is greater than a shaft diameter. In some embodiments, the distal housing is flexible to accommodate passage of a straight tool through a curved distal portion of a working channel. In some embodiments, a curved distal portion of a working channel may be reoriented to deflect a flexible tool.
