A centrifugal pump with an outer casing which has one or more discharge branches, with an inner casing which is installed in the outer casing and rotatably surrounds a pump shaft, and an impeller which is mounted on the shaft at the inlet of the outer casing has one or more fluid flow guiding inserts, one for each discharge branch, in an annular chamber between the inner and outer casings. The inserts are offset relative to the respective discharge branches in the direction of rotation of the shaft and have front faces provided on spur-shaped front portions immediately behind the exit end of the impeller. The inserts further have guide surfaces including first sections adjacent the inner casing, second sections adjacent the outer casing, and third sections which direct a portion of the fluid medium directly from the exit end of the impeller to the corresponding discharge branches. The guide surfaces establish for the fluid medium a path which resembles that defined by the thread on a shank forming part of a screw and having a diameter which increases in a direction from the exit end of the impeller toward the discharge branches of the other casing.