What does "ultrafiltration" refer to in hemodialysis?

Ultrafiltration in hemodialysis refers specifically to the process of removing excess fluid from the blood. This is achieved by creating a pressure gradient across a semi-permeable membrane in the dialysis machine, allowing water and small solutes to move out of the blood and into the dialysate while retaining larger molecules like proteins and blood cells. This mechanism is crucial for patients with kidney failure, who may retain excess fluids due to their kidneys' inability to remove them effectively. By utilizing ultrafiltration, the dialysis process helps to maintain proper fluid balance in the body, which is essential for overall health and well-being in these patients.