An apparatus for drainage of a body fluid in a human or mammal patient, comprising: - a drainage device, - an energy source adapted to supply energy to said drainage device, and - at least one connecting tube connected to said drainage device, the drainage device and the tube forming a drainage arrangement, wherein the drainage device is adapted to be implanted inside the body of the patient, and wherein said tube interconnects one part of the body with another part of the body and said drainage device is adapted to suck body fluid from the one part of the body via the connecting tube to the other part of the body, characterized in that the drainage device includes an expanding reservoir comprising: - a bellow having an inlet with an inlet valve adapted to prevent fluid from exiting via the inlet when the bellow is compressed, and an outlet with an outlet valve adapted to prevent fluid from entering via the outlet when the bellow is expanded, - a member adapted expand and compress the bellow, and - a motor adapted to drive the member to expand the bellow to suck fluid and to compress the bellow and move fluid out, wherein said drainage device is adapted to continuously repeat expansion and compression of the bellow, whereby body fluid is removed from the treatment area to the delivery area. - a drainage device, - an energy source adapted to supply energy to said drainage device, and - at least one connecting tube connected to said drainage device, the drainage device and the tube forming a drainage arrangement, wherein the drainage device is adapted to be implanted inside the body of the patient, and wherein said tube interconnects one part of the body with another part of the body and said drainage device is adapted to suck body fluid from the one part of the body via the connecting tube to the other part of the body, characterized in that the drainage device includes an expanding reservoir comprising: - a bellow having an inlet with an inlet valve adapted to prevent fluid from exiting via the inlet when the bellow is compressed, and an outlet with an outlet valve adapted to prevent fluid from entering via the outlet when the bellow is expanded, - a member adapted expand and compress the bellow, and - a motor adapted to drive the member to expand the bellow to suck fluid and to compress the bellow and move fluid out, wherein said drainage device is adapted to continuously repeat expansion and compression of the bellow, whereby body fluid is removed from the treatment area to the delivery area. wherein the drainage device is adapted to be implanted inside the body of the patient, and wherein said tube interconnects one part of the body with another part of the body and said drainage device is adapted to suck body fluid from the one part of the body via the connecting tube to the other part of the body, characterized in that the drainage device includes an expanding reservoir comprising: - a bellow having an inlet with an inlet valve adapted to prevent fluid from exiting via the inlet when the bellow is compressed, and an outlet with an outlet valve adapted to prevent fluid from entering via the outlet when the bellow is expanded, - a member adapted expand and compress the bellow, and - a motor adapted to drive the member to expand the bellow to suck fluid and to compress the bellow and move fluid out, wherein said drainage device is adapted to continuously repeat expansion and compression of the bellow, whereby body fluid is removed from the treatment area to the delivery area. - a bellow having an inlet with an inlet valve adapted to prevent fluid from exiting via the inlet when the bellow is compressed, and an outlet with an outlet valve adapted to prevent fluid from entering via the outlet when the bellow is expanded, - a member adapted expand and compress the bellow, and - a motor adapted to drive the member to expand the bellow to suck fluid and to compress the bellow and move fluid out, wherein said drainage device is adapted to continuously repeat expansion and compression of the bellow, whereby body fluid is removed from the treatment area to the delivery area.