Principles of renal replacement therapy: what dialysis and transplantation replace

At a glance

• The kidney excretes water-soluble waste, regulates volume, electrolytes and acid-base, and makes or activates hormones. Dialysis replaces only the first two groups, and only partly. A transplant replaces all of them.
• Dialysis moves solutes by diffusion (small molecules), convection (middle molecules) and adsorption, and removes water by ultrafiltration.
• Haemodialysis adequacy is measured as Kt/V urea or the urea reduction ratio. Peritoneal dialysis depends on the patient's own membrane transport.