A medical device for shutting off an anatomical channel is provided, including: a band section that can be placed around the body tissue surrounding said body channel and can be closed to form a ring enclosing a passage opening for the body tissue, and that includes a cavity which makes up one part of a receiving chamber of the arrangement, for receiving working fluid； and a pump unit for conveying said working fluid. The passage opening can be made smaller by introducing the working fluid into the cavity. The device includes an expansion body having an expansion chamber, wherein the expansion body is arranged in the receiving chamber for the working fluid or on the band section, on a side of said band section that faces the passage opening, and the expansion chamber can be made bigger by introducing an auxiliary fluid, which is separate from the working fluid, into the expansion chamber.
