Allo-Hemodialysis: A Narrative Review of a Novel Approach to Resource-Sparing Kidney Replacement Therapy

Conventional hemodialysis (HD) is one of the most resource-intensive therapies in medicine and remains inaccessible to a large share of the world’s population with kidney failure. Allo-hemodialysis (alloHD) is a novel hemodialysis concept in which the blood of a healthy volunteer (“buddy”) replaces manufactured dialysate, flowing counter-currently to the patient’s blood across a conventional dialyzer membrane. Uremic solutes and excess fluid move from the patient into the buddy’s circulation and are cleared by the buddy’s own kidneys, while bicarbonate and water-soluble vitamins diffuse back to the patient. By eliminating water treatment, dialysate production, and much of a conventional machine’s electromechanical complexity, alloHD has the potential to lower the cost, complexity, and environmental footprint of kidney replacement therapy. This review synthesizes the evidence for alloHD, spanning two-compartment urea and acid–base kinetic modeling, ex vivo bench testing of a low-cost prototype, and in vivo porcine studies of acute kidney injury, while describing a modeling extension to severe neonatal jaundice. We summarize buddy safety considerations as well as review ethical issues and caregiver/health-care professional acceptance data. Finally, we position alloHD within the broader movement toward more sustainable and personalized dialysis, and outline the translational steps required before first-in-human study.