An arrangement in connection with the handling of patient fluids, comprising a suction canister open at one end, a cover for closing the suction canister, a suction bag fastened to the cover, and an underpressure apparatus for applying underpressure to a space between the suction canister and the suction bag. The arrangement further comprises fastening means for keeping the suction bag narrowed in such a manner that the width and length of the suction bag are at least along part of the suction bag smaller than when the suction bag is opened, and the fastening means are arranged to release the suction bag to be opened into the suction canister under the action of the underpressure when the cover is closed.
