The standard Dialysis is a technique based dialysis . In it, the purification process relies mainly on the physical phenomenon of diffusion which allows better to purify solutes low molecular weight ie urea and creatinine.

The hemofiltration in pre-post-dilution (HF) is a dialysis technique exclusively convective , now rarely used due to the introduction of mixed techniques. The method involves the use of high permeability filters and reinfusion to the patient of large amounts of liquid: 40 Lt. It is also indicated in hemodynamically unstable patients and requiring a high purification.

The hemodiafiltration (HDF) is a convective-diffusive dialysis method in which the diffusion allows the purification from low molecular weight substances , while the convection allows the purification from the medium-molecular weight substances. The reinfusion can be carried out pre-filter and post filter. Pre filter is possible reinfodere a greater amount of liquid and in the convection-diffusion ratio favors the first eliminating the macromolecules and doing arrive at the blood filter diluted.Post Filter is privileged convection because the blood reaches the undiluted filter. High permeability filters are needed. It is important to find the right gear convection diffusion. It is useful in patients requiring a high purification.

The on-line hemodiafiltration (HDF on-line) and the reinfusion takes place not through pockets, but directly from the water system of the dialysis center. The water after it has been deionized, is rendered sterile and apirogenada ultrafilters by two places on the back of the machine. It allows reinfusioni flows greater than all’HDF. The reinfusion can be pre- or post-filter, depending on the specific device characteristics and dialysis prescription.