A system for treating an aneurysm comprises at least a first double-walled filling structure having an outer wall and an inner wall and the filling structure is adapted to be filled with a hardenable fluid filling medium so that the outer wall conforms to the inside surface of the aneurysm and the inner surface forms a generally tubular lumen to provide blood flow. The first filling structure comprises a sealing feature which forms a fluid seal between the filling structure and the aneurysm or an adjacent endograft when the filling structure is filled with the hardenable fluid filling medium, thereby minimizing or preventing blood flow downstream of the seal.
