Apparatus for forming and enlarging a percutaneous penetration are disclosed. The apparatus includes an elongate dilation member including a radially expandable member having a first cross-sectional area; and an elongate expansion member including a tubular element having a second cross-sectional area which is larger than the first cross-sectional area. The apparatus further includes an advancing apparatus having a first arm with a first engaging feature for engaging the handle of the dilation member; a second arm with a second engaging feature for engaging the handle of the expansion member; and an operation member; the first arm and the second arm being connected so that operation of the operation member approximates the first engaging feature and the second engaging feature together.