A device for treating a vascular aneurysm of a human or mammal patient, comprising an implantable member adapted to hold fluid, the implantable member being adapted to be placed against an outside of a blood vessel having the aneurysm, exercise a pressure on the aneurysm to prevent or reduce an expansion of the aneurysm, follow an outer contour of the aneurysm, and provide a pressure that is equal or less than the diastolic blood pressure of the human or mammal patient.