An embodiment of an apparatus for locating a surface of a body lumen is disclosed. The apparatus includes a locator assembly that has a distal end region configured to extend into an opening of the body lumen and to selectably engage at least a portion of the body lumen adjacent to the opening. The distal end region includes at least one surface engaging element that is configured to engage the surface of the body lumen. The apparatus includes a measuring device that is in electrical communication with the surface engaging element. The measuring device is configured to determine changes in measurable characteristics of the surface engaging element. Methods and apparatus for locating a surface of a body lumen are also disclosed.
