A surgical instrument for use with a surgical portal apparatus is disclosed. The surgical instrument includes an elongate shaft and a dilating member disposed at the distal end of the elongate shaft. The elongate shaft has proximal and distal ends and defines a longitudinal axis. The dilating member has an outer surface that includes at least one atraumatic edge member. The at least one atraumatic edge member extends proximally from a tip of the dilating member. The dilating member has a first substantially triangular cross-section disposed transverse to the longitudinal axis.
