How does hemodialysis work as an artificial kidney?

Hemodialysis functions as an artificial kidney by removing blood from a patient with faulty kidney function, purifying it, and returning it to the bloodstream. The process relies on two primary physicochemical principles:1

• Dialysis: Blood flows along one side of a porous membrane, while a sterile solution flows on the other. Small particles, such as urea and inorganic salts, diffuse through the membrane into the solution. Larger components like blood cells and proteins are too big to pass through. To prevent the loss of essential nutrients like sugars and amino acids, these are added to the sterile solution to balance their concentration.1
• Ultrafiltration: Because water does not naturally move out of the blood during dialysis, ultrafiltration is used to remove excess fluid. By maintaining the blood at a higher pressure than the sterile solution, water and dissolved materials are forced through the membrane.1

While this apparatus effectively manages waste, water balance, and acid-base levels, it cannot replicate the natural kidney's function of secreting hormones that regulate blood pressure.1