A cannula assembly includes a cannula adapted for insertion within tissue and having a longitudinal passage extending along a longitudinal axis of the cannula for passage of a surgical instrument. An expandable member is mounted to the cannula and longitudinally spaced from a distal end of the cannula. The expandable member is adapted to expand, upon introduction of fluids therein, in a radially outward direction relative to the longitudinal axis whereby the expandable member engages the tissue to facilitate anchoring of the cannula relative to the tissue, and also to expand in a radially inward direction relative to the longitudinal axis and within the longitudinal passage to engage the surgical instrument positioned within the longitudinal passage to facilitate formation of a seal about the surgical instrument.