I went through mine fully anticoagulated with no problems and 2 polyps removed. That wasn't the plan, but that's the way it went. The plan was to go look and if something was found, to take me off and then do the procedure again. If yours wants you to stop, do not do so without being bridged with either heparin or lovenox.
Usually it's stop 3 to 5 days before the procedure, but being bridged the entire time until 12 hours before the procedure, then resume bridge and take your first dose of Coumadin 12 hours after the procedure and continue the bridge until your INR is in range.