Hemodialysis system having a flow path with a controlled compliant volume

A method for performing enhanced convective clearance with reduced risk of blood clotting, comprising:

• attaching the vasculature of a subject to a system for kidney replacement therapy having an extracorporeal circuit having a first end that draws blood from the subject and a second end that returns blood to the subject, wherein the extracorporeal circuit is in fluid communication with a controlled compliance dialysis circuit through a dialysis membrane housed in a dialyzer;
• conveying blood from the subject through the extracorporeal circuit and the dialyzer and returning the blood to the subject;
• conveying a dialysate through the dialysis circuit such that the dialysate moves from a sorbent cartridge, to the dialyzer and back to the sorbent cartridge, where at least one waste species diffuses from the blood to the dialysate through the dialysis membrane and the sorbent cartridge substantially removes at least one impurity or waste species from the dialysate;
• and
• operating a control pump that adds fluid from a control reservoir to the dialysis circuit in an influx direction via a conduit or removes fluid from the dialysis circuit to the control reservoir in an efflux direction via the conduit, and intermittently switching the control pump between the efflux direction to move fluid across the dialysis membrane from the extracorporeal circuit to the dialysis circuit and the influx direction to move fluid across the dialysis membrane from the dialysis circuit to the extracorporeal circuit.
• wherein the intermittent switching of the pump accomplishes the convective clearance of at least one waste species.

A system for performing kidney replacement treatment, comprising:

• a hemofiltration system having a controlled compliance filtration circuit, a hemofilter with a hemofiltration membrane, a blood inlet end for receiving blood, a blood outlet end for allowing blood out of the hemofilter, and an ultrafiltration outlet for allowing an ultrafiltrate out of the hemofilter;
• an extracorporeal circuit having a conduit for receiving blood from a subject and a conduit for returning blood to the subject, and a blood pump for conveying blood from the subject, to the hemofilter and back to the subject;
• a hemofiltration circuit having a sorbent cartridge for removing at least one impurity or waste species from the ultrafiltrate to generate a replacement fluid, wherein the ultrafiltrate enters an inlet end of the sorbent cartridge and a replacement fluid exits an outlet end of the sorbent cartridge, the hemofiltration circuit having one or more conduits and a filtrate pump for conveying the ultrafiltrate from the hemofilter to the sorbent cartridge and for infusing the replacement solution into the extracorporeal circuit;
• and
• one or more controllers for controlling a rate of the blood pump and a rate of the filtrate pump.