A blood filtration device (10) comprising a generally cylindrical housing (12) having an interior wall. An interior member (14) is mounted interior of the housing and comprises an outer surface having a porous membrane (62) disposed thereon. The housing and interior member are relatively rotatable and define an annular gap (16) therebetween. The blood filtration device also comprises an inlet for directing fluid into the annular gap, a first outlet (46) for exiting filtrate passing through the membrane, and a second outlet for directing from the annular gap the remaining retentate. The porous membrane comprises a first layer and a second layer.
