A tissue ablation device comprising a balloon catheter, or other expandable element, wherein said expandable element is comprised of a semipermeable membrane. The balloon membrane is expanded by an osmotically active solution to contact a vascular endothelium, or other desired tissue, whereupon the resultant osmotic gradient affects a water flux from the vascular endothelium, or other desired tissue, across the semipermeable membrane and towards the osmotically active solution.
