One of the most important functions of the natural kidney, in addition to the filtering of uremic toxins, is the removal of excess water from the body. When the kidneys fail, this function must be taken over by the artificial kidney, which is also known as a dialyzer. This procedure is termed “ultrafiltration” and squeezes plasma water from the patient through the dialyzer membrane using pressure.


Alwall dialyzer

In 1947, the Swede Nils Alwall published a scientific work describing a modified dialyzer developed between 1942 and 1947 that could better combine the necessary processes of dialysis and ultrafiltration than the traditional Kolff kidney. The cellophane membranes used in this dialyzer could withstand higher pressure because of their positioning between two protective metal grates. All of the membranes were in a tightly closed cylinder so that the necessary pressure did not have to come along with the blood but could rather be achieved using lower pressure in the dialysate.