In the past, tract dilation was accomplished using either metallic telescoping dilators (the Alken system) or Teflon-coated graduated dilators (the Amplatz system). At present, however, most centers use balloon-dilating systems. These offer single-step dilation that causes less bleeding than previous systems because of the application of radial, rather than shear, force. In balloon dilation, a deflated balloon with a hollow core is passed over the previously deployed wire. The balloon contains radiopaque markers at its proximal and distal edges to ensure proper positioning. The balloon is then inflated under pressure. Once the balloon is turgid, a plastic sheath can be deployed over the balloon. The balloon is then deflated and removed, while leaving the sheath in position for continued renal access.