The disclosure relates to devices and methods for the treatment of edema using a purge-free system. The invention provides devices and methods useful for treating edema by means of an indwelling catheter that is placed in a blood vessel of a patient and used to pump blood to cause a decrease in pressure at an outlet of a lymphatic duct. The catheter pumps blood by means of an impeller but is purge-free in that the catheter does not include a system for purging or flushing catheter components with a purge fluid. The purge-free catheter avoids blood-related mechanical complications such as clotting or thrombosis by means of an impermeable sleeve or shroud that protects moving parts of the impeller drive system.
