The disclosed subject matter describes systems and methods of delivering a therapeutic agent, such as a sclerosing agent, to the walls of a blood vessel to perform sclerotherapy. In an exemplary embodiment a catheter includes a balloon having an inner and outer surface defining a wall, and an interior volume with an unexpanded and expanded configuration and a plurality of fibers extending from the outer surface of the balloon wall. In another exemplary embodiment, a balloon catheter comprises a catheter having a balloon with an unexpanded and an expanded configuration, and a retractable sheath disposed on the exterior surface of the balloon, wherein the sheath has an inner surface and an outer surface, and further wherein a plurality of fibers outwardly extend from the outer surface of the sheath.