A self-retracting body, which may have a bore, may be inserted into a biological passage. A dilating balloon may be used to expand the body toward an inner wall of the passage. The body may include an anchor that may engage the wall. The anchor may include a tip that is within the body before the body expands and extends away from the body during expansion. The body may include an opening that may receive a portion of the wall. The portion may be fixed to the body. The body may retract toward a central portion of the passage after the anchor engages the wall. The wall may be drawn toward the central passage and the diameter of the passage may be reduced. In some embodiments, a liner may be provided for the passage. In some embodiments, a baffle may be provided for the passage.