An apparatus and method for replenishing urease in a sorbent cartridge for use in sorbent dialysis. The system is configured to allow insertion of a urease pouch injection of a urease solution or addition of a urease cartridge into a dialysis cabinet containing a dialysis flow loop. The urease can be dissolved and the resulting urease solution added to the sorbent cartridge in the flow loop to replenish the urease within the sorbent cartridge. The sorbent cartridge can also comprise other rechargeable sorbent materials for removing toxins other than urea from spent dialysate.
