One aspect of the invention provides a trocar including: a central cylinder defining a central channel and having a distal end adapted and configured for insertion within a subject； one or more gas outlets located within the central cylinder proximate to the distal end of the trocar； and one or more liquid outlets located within the central cylinder on a proximal side of the one or more gas outlets. The one or more liquid outlets are adapted and configured to dispense a liquid when an endoscope is withdrawn from a fully extended position within the central channel of the trocar to a position proximate to the one or more liquid outlets. Distal advancement of the endoscope to a position adjacent to the one or more gas outlets removes liquid from a distal end of the endoscope.
