Percutaneous access systems, including trocars, for accessing desired locations within a subject's body through the subject's skin or other tissues that are configured to minimize incision sizes are disclosed. Such a percutaneous access system includes a cannula and an obturator. The cannula includes a passageway with a tapered section and an expandable section at its distal end. The expandable section may include leaves that are configured to extend radially outward as an elongated instrument that has an outer diameter that exceeds a minimum relaxed inner diameter of the tapered section of the passageway is forced through the tapered section. Methods for using such a percutaneous access system, including medical procedures, are also disclosed.
