Is it ensure, insure, or assure?
endoscopy en·dos·co·py (ěn-dŏs'kə-pē)
Examination of the interior of a canal or hollow organ by means of an endoscope.
A medical instrument used for visual examination of the interior of a body cavity or a hollow organ such as the colon, bladder, or stomach. It is a rigid or flexible tube fitted with lenses, a fiber-optic light source, and often a probe, forceps, suction device, or other apparatus for examination or retrieval of tissue.
endoscopy noun (ěn-dŏs'kə-pē)