Backfiltration (BKF) in single needle dialysis

Backfiltration (Bkf) is a potentially very dangerous phenomenon in haemodialysis, when chemical or biological contamination is present in the dialysate. It occurs when the dialysate pressure within the filter exceeds the pressure in the blood compartment, i.e. when Pbo < Pdi + pi o (where Pbo = the hydrostatic blood pressure at the filter outlet, Pdi = hydrostatic dialysate pressure at the filter inlet, pi o = oncotic pressure at filter outlet).