(ultrafiltration) Filtration through filters with minute pores; occurs naturally, as in the filtration of plasma at the capillary membrane, and is performed in the laboratory, especially to separate a substance in colloidal solution from its dispersion medium.

(ultrafiltration) The filtration of a colloidal substance through a semipermeable medium that allows only the passage of small molecules.

(ultrafiltration) The separation of particles from a suspension by passage through a filter with very fine pores. In ultrafiltration the separation is accomplished by convective transport; in DIALYSIS separation relies instead upon differential diffusion. Ultrafiltration occurs naturally and is a laboratory procedure. Artificial ultrafiltration of the blood is referred to as HEMOFILTRATION or HEMODIAFILTRATION (if combined with HEMODIALYSIS).