A surgical tool for use in expanding a tubular structure having an inner surface defining a passage through the tubular structure for receiving surgical instruments includes a first leg having a first end engageable with the inner surface of the tubular structure. A second leg has a second end engageable with the inner surface of the tubular structure. The first and second ends are movable away from each other to apply a radially outwardly directed force to the inner surface of the tubular structure and cause expansion of the tubular structure to increase a cross-sectional area of the passage along a portion of the passage.