The present invention relates to systems and methods for filtration and/or dilution of fluids, in particular for the dialysis of blood. The systems comprise a filter device (10) having a fluid chamber (18) and comprising a first lid (20) having arranged thereon a first fluid port (22). The filter device (10) further comprises a second lid (30) having arranged thereon at least a second fluid port (32). The filter device (10) further comprises a plurality of hollow fibers (40) arranged within the housing (12), wherein each of the plurality of hollow fibers (40) comprises a semi-permeable membrane and defines a fluid channel extending longitudinally through an interior of the respective hollow fiber (40). Also, the filter device (10) comprises a fourth fluid port (50) and a fifth fluid port (52) both provided at the fluid chamber (18).
