A device for creating a fistula between blood vessels operates in conjunction with a guidewire to locate and position itself so that it straddles both vessels and is able to draw them together. A fixing agent is released either from within the device or from an external needle, or both, into the procedural site. The fixing agent functions to hold the relative position of the two vessels, to seal the surrounding tissue so that any leaks that do occur don't spread into the tissue to create a hematoma, and to limit expansion of the fistula. After the vessels are in close proximity to each other and the fixing agent is applied, the device of the invention employs a cutting mechanism which opens a portal between the two vessels.