Abstract: A vena cava thrombus filter includes a catheter for insertion in a vein including a tube of flexible plastic and a guiding and holding wire supported and axially displaceable in the tube. The distal end of the wire has a filter element formed of wires which are elastically expandable inside a vein, wherein, in a forwardly pushed position outside of the catheter insertion end, the wires can expand to form a basket through which liquid can flow. The catheter has at the handling end of the guiding and holding wire a handle, and a fitting closable to irrigation fluid provided with a bayonet lock for fastening the handle relative to the fitting. The fitting has a metallic guide sleeve, wherein the flexible tube of the catheter is pulled over the metallic guide sleeve. A flexible rubber or plastic sleeve is arranged over the metallic guide sleeve and the flexible tube pulled over the metallic guide sleeve.