A method for occluding a body vessel in a patient to block or reduce blood flow therethrough includes puncturing a blood vessel wall at a proximal vessel entry site with a hollow needle and extending the needle through the proximal entry site into the vessel lumen. The needle is extended through the vessel lumen and extended through the vessel wall at a distal vessel exit site into the extravascular space surrounding the distal vessel exit site. An expandable biocompatible material, such as expandable extracellular matrix (ECM) material, is then ejected though the distal end of the needle into the extravascular space. Then, while continuing to eject the expandable biocompatible plug material, the distal end of the needle is retracted back through the distal vessel exit site into the vessel lumen, such that the plug material continuously extends between the extravascular space surrounding the distal vessel exit site into the vessel lumen. When the plug material is delivered into the lumen of the vessel, the plug material expands, anchoring the plug material to the vessel wall, whereby the plug material forms an occluding plug in the vessel lumen blocking or reducing blood flow therethrough.
