Apparatus for driving fluid between first and second anatomical sites of a subject is provided, comprising (1) a first electrode, configured to be coupled to the first anatomical site of the subject (2) a second electrode, configured to be coupled to the second anatomical site of the subject and (3) a control unit, configured to (i) detect a pressure difference between the first and second anatomical sites, and (ii) in response to the detected pressure difference, drive fluid between the first and second anatomical sites by applying a treatment voltage between the first and second electrodes. Other embodiments are also described.
