Medical systems and methods for making and using medical systems are disclosed. An example may include a catheter, a sensor, and a pump configured to remove contrast from a vascular system. The catheter may have a lumen through which the pump may suction contrast. The sensor may be positioned distal of and upstream of a distal end of the aspiration lumen and the pump may initiate suction through the lumen in response to a value sensed by the sensor reaching and/or going beyond a threshold value. The catheter may include an expandable member configured to expand in response to a value sensed by the sensor reaching and/or going beyond a threshold value. The sensor may be supported by a distal extension of the catheter or an elongate member configured to extend through and/or along the catheter to position the sensor distal of the distal end of the aspiration lumen.
