A device and method for treating bodily diseases and/or conditions, for example, varicose veins, tumors and aneutisms including for example insertion of a blocking device toward a target destination using a catheter and delivery of sclerosing or other agents to the vessel while maintaining minimal, for example zero pressure in the treatment area, The blocking device may prevent treatment materials, embolisms, debris etc., from entering the upstream section of vessel. The blocking device may include, for example, a cap or other concave shape and may be expandable or extendible towards the vessel walls.