An endoscope with a rigid inserted portion intended for surgical treatment of the lower part of the bowel during transanal endoscopic microsurgery (TEM) or transanal endoscopic operations (TEO). It is inserted into the body through the anus; an obturator may be inserted into its lumen to assist the insertion. Anatomical images are transmitted to the user by the device through the inserted optical viewing telescope. It also has facilities to introduce gas to distend the field of view while allowing the insertion of dedicated endotherapy/surgical instruments via gastight ports. This is a reusable device.