Systems and methods for extracorporeal processing of blood or other body fluid for the treatment of conditions, such as sepsis, autoimmune disease, or toxemia related to kidney failure, liver failure, or drug overdose are provided. In an extracorporeal treatment system, a fraction of a body fluid is passed into a treatment fluid, at least a portion of which is then passed through a sorbent suspension reactor for treatment by a sorbent suspension. The treatment fluid circuit can be maintained at a fixed volume, which enables accurate fluid balance between the patient and the extracorporeal circuit. Some or all of the treatment fluid, optionally also containing nutrients and/or therapeutic agents, is returned to the patient. In a peritoneal dialysis system, dialysate is passed into a patient's peritoneal cavity, recovered from the cavity, passed through a sorbent suspension reactor in accordance with the invention, and returned to the cavity.