A system includes a dialyzer having a blood side and a dialysate side, a first extracorporeal circuit including one or more first fluid connectors structurally configured to connect the blood side of the dialyzer to the vascular system of a kidney patient, and a second extracorporeal circuit including one or more second fluid connectors structurally configured to connect the dialysate side of the dialyzer to the vascular system of a healthy animal. The present teachings may thus include a system where hemodialysis is performed using a healthy animal (e.g., a person with normal kidney function) to help remove harmful solutes from, and provide helpful solutes to, a kidney patient. In this manner, the healthy animal is “virtually donating” its kidney function to the kidney patient.