What process is used to remove excess fluid from the blood during dialysis?

The process used to remove excess fluid from the blood during dialysis is ultrafiltration. In dialysis, particularly in a hemodialysis setting, ultrafiltration plays a crucial role in eliminating excess water and solutes from the blood. This is achieved by creating a pressure gradient across the dialysis membrane, which allows fluid to be removed from the blood without the need for the solutes themselves to follow.

Ultrafiltration is specifically used to regulate fluid balance and prevent complications associated with fluid overload in patients with renal failure. While diffusion and osmosis also occur during dialysis, they are primarily responsible for the movement of solutes rather than water.

Diffusion is the process where solutes move from an area of higher concentration to an area of lower concentration through the dialysis membrane, while osmosis involves the movement of water across a semipermeable membrane in response to solute concentration differences. However, when it comes to the targeted removal of excess fluid, ultrafiltration is the primary mechanism at work.