Abstract: Various catheter systems using a patient's own bodily fluids to increase local fluid velocity and therefore localized lower pressure via the Venturi effect. Exemplary systems utilize a pump to suction and eject blood to/from an attached catheter. One catheter comprises a valve moveable such that the area of the opening at the distal end for fluid passage is larger during suction than during ejection. Another catheter comprises openings in the sidewall and a balloon at the distal end to temporarily occlude the vessel during suction. Another catheter comprises a narrow distal opening and multiple openings with valves in the catheter sidewall. When catheters are deployed near a lymphatic opening into the circulation, such as at the thoracic duct, the ejection of blood from the catheter may cause a localized pressure reduction aiding in the reintroduction of lymph into the circulation.