Spiral exchange cannula for the occluded drainage catheter.

A technique for exchange of occluded drainage catheters or placement of two guide wires into a target using a spiral exchange cannula is described. A spiral exchange cannula with a preloaded sheath and threads at the distal end is "screwed" into the drainage catheter, and the sheath is advanced over the catheter. This method prevents dislodgment of the drainage catheter and also permits easy catheter exchange when the lumen of the drainage catheter is occluded.