A dialysis machine is just a nephron you can unplug
The kidney does not "clean" blood — it does membrane exchange, solute by solute, across a million tiny filters. When kidney function drops, a dialysis machine replicates the same process using the same physics. Drag the slider to throttle kidney function and watch the machine take over the exchange.
Filter Exchange
100% Nephron / 0% Machine
Blood flows through both circuits — solutes cross membranes where concentration differs
Healthy kidney filtering — machine idle
Kidney Function
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Waste Removed
100%
Hours/Week
0h
Haemodialysis routes blood out of the body through a machine containing thousands of hollow fibres bathed in dialysate fluid. Blood flows inside the fibres, dialysate flows outside in the opposite direction. Waste molecules like urea and creatinine diffuse from blood to dialysate across the semi-permeable fibre walls, following their concentration gradient. The machine also applies negative pressure to pull excess water from the blood — ultrafiltration that mimics what a nephron does when it adjusts water balance. Each session runs three to four hours, three times per week, and patients must restrict potassium and phosphate in their diet because the machine cannot regulate these as precisely as a living kidney. The technology manages kidney failure but does not cure it — the moment dialysis stops, waste begins accumulating again.
Know This
Dialysis is membrane exchange using the same concentration gradient physics as a nephron, but it requires 12 hours per week to do what healthy kidneys do continuously, which is why it manages but never replaces kidney function.