US Patent 9345856 Medical catheter with reduced backflow

A medical catheter (1) comprising an inner catheter tube (2) and an outer catheter tube (3), wherein the inner catheter tube (2) has at least one outlet port (6) for a medical liquid at its distal end and the outer catheter tube comprises two parts of differing rigidities, namely a flexible part (5) and a rigid part (4), wherein the flexible (5) part is located at the distal end of the outer catheter tube (3) and the distal end of the flexible part (5) is connected to the inner catheter tube (2), and wherein the medical catheter also comprises a drive means (7) for generating a relative movement between the inner catheter tube (2) and the rigid part (4) of the outer catheter tube (3).