The present invention is a measuring device for determining the insertion distance of an endoscope in a body lumen during an endoscopy. The measuring device generally may include a bracket member for attaching the measuring device to an endoscope, a spooling device for spooling thread wrapped around a thread disk attached to the spooling device, and a thread tension knob. Prior to an endoscopy, the biocompatible thread may be attached to the lumen interior, such as the small intestine wall. As the endoscope is removed from the lumen, the thread unwinds from the thread disk as the spooling device rotates during the spooling process. A counting device counts the rotations of the spooling device. The number of rotations may subsequently be translated to linear distance so that a location within the lumen may later be correlated to images taken during the endoscopy.
