A cartridge is provided for dialysis or other blood processing therapy. In the cartridge, fibers may be substantially uniformly distributed near a midplane, but near an end, in the inter fiber space, there may be void flow channels, which may cause fluid flow in the inter fiber space to transition within a short region to uniform flow with minimal stagnation zones. Void flow channels may be be radially oriented, introducing fluid from the outer circumference, or axially oriented, introducing fluid along the axial direction through passageways through the potting material. The fluid flow in the inter fiber space may be perpendicular to the fibers, or radial with respect to a cartridge longitudinal axis. The cartridge may have blood flow in the inter fiber space, and flow of dialysate or ultrafiltrate in the lumens of the fibers, or the opposite situation.

Disclosed herein are aspects and embodiments of filtration membrane modules including porous membranes and methods and structures associated with potting ends of the porous membranes in the membrane modules. In one example, there is provided a method of forming a filtration module. The method comprises securing a portion of a porous membrane in a pre-pot, positioning at least a portion of the pre-pot in a potting mold, introducing a pot forming substance into the potting mold, the pot forming substance surrounding at least a portion of the pre-pot and at least a portion of the porous membrane, curing the second pot forming substance to form a membrane pot, and separating the membrane pot from the potting mold.

A hollow fiber membrane module 10 has a hollow fiber membrane bundle 11 and a housing case 15. The housing case 15 has first molding members 17 and a second molding member 18. At each first molding member, a tubular portion 19 and a nozzle portion 20 are integrally molded. The second molding member 18 has a tubular shape coaxially continuous from the tubular portion 19. Values obtained by dividing, by the wall thickness of the second molding member, the wall thicknesses of the housing case 15 at positions separated in the axial direction from a connecting position toward the first molding member 17 side by distances of 3 times and 5 times the wall thickness of the second molding member 18 are 1.0 to 1.3 and 1.0 to 1.5, respectively.