This is an enhancement and/or modification of the ultrasound-guided foam sclerotherapy of the main vein. Prior to the injection of the obliterating foam a small metal umbrella is placed through a catheter access at the calf into the diseased vein, in front of the junction with the deep vein system. This prevents the foam from entering circulation and intensifies the effect of the obliterating liquid. The stent remains in the vein, folds up like a small umbrella in the course of the scarred contraction of the treated vessel and this way it reduces the risk of recanalization, i.e. the re-opening of the vessel. For the aftercare of v-block-supported treatment the same measures apply as to foam sclerotherapy alone.