A system and method for determining the path length through a body lumen, for example to a specified location, is described. A location detection system may identify the location in space of an in-vivo device over time. A path-length detection unit may use data from the location detection system to determine a path traveled by an in-vivo device. A site of interest along that path may be identified. The distance of the site of interest from at least one end point of a body lumen may be determined.