A hemodialyzer with expanded solute removal profile is intended for use as part of an artificial kidney system for the treatment of patients with renal failure by performing such therapies as hemodialysis, hemofiltration, and hemodiafiltration. A hemodialyzer with expanded solute removal profile includes modifications to the semipermeable membrane that allows for increased removal of uremic retention solutes compared with standard high-flux hemodialyzers of the high permeability hemodialysis system classification (21 CFR §876.5860), including solutes at the upper end of the “middle” molecular weight range (0.5 kDa to 60 kDa).