Understanding dialysis and how a dialyzer works
Dialysis is a medical procedure which is conducted when a person has chronic kidney failure. Hemodialysis and peritoneal dialysis procedures replicate some of the essential functions of the kidneys. These include the removal of waste products like various toxins, surplus salt and other impure liquids from the body.
One of the key components of a dialysis procedure is a dialyzer. It is an artificial filter which consists of fine fibers. The fibers are hollow and have microscopic pores on its walls. These pores are called semi-permeable dialysis membrane. The toxins are removed via a dialysis-fluid flow through the filter from outside. The blood goes through the hollow space in the fibers and as the membranes are semi-permeable, urea and other fragments flow through.
The metabolic toxins can flow through the dialyzer membranes into the dialysis fluid via diffusion. Blood and the dialysis liquid consisting of various molecule concentrations are kept separate by the membranes. When this happens, the molecules move through the membrane to a lower density. But, large particles such as protein and blood cells remain in the blood as they can’t pass through the membrane.
Peritoneal dialysis is used to take out the excess water. During this process, sugar is added to the dialysis liquid. Since sugar molecules cannot flow through the peritoneum membrane, body water goes through the membrane and into the dialysis fluid. This process balances the difference in concentration and is called osmosis.
However, in hemodialysis, an artificial membrane is used. Here, if the pressure on the outside of the hollow fiber is lower than the inside, then the water content goes out from the blood, passing through the hollow fiber. This function is known as ultrafiltration.
Another procedure used during hemodialysis is convection. Convection is one of the vital processes in hemodiafiltration which is an effective form of hemodialysis. In this process, the water contents are made to pass through the dialyzer membrane via hydrostatic pressure. Due to the pressure, water along with other toxins and waste particles are dragged out through the membrane.