1. Dialysis - The Artificial Kidney What is it? Dialysis is a form of treatment that replicates many of the kidney’s functions. It is often used to treat advanced chronic kidney disease, where the kidneys have lost most or all of their function. This is known as kidney failure or end stage renal disease. Every day the kidneys filter your blood, removing waste products such as urea, collected as part of normal bodily functions, along with any excess fluid. The waste products and excess fluid become urine, which is stored in the bladder until you go to the toilet. How long is a person on dialysis? Many people will remain on dialysis on a long-term basis (possibly for the rest of their lives) but for a significant minority the goal will be a kidney transplant. It takes around 8 hours for each dialysis treatment to be complete. You have to remain attached to the dialysis machine for many hours, several times a week! Diets also have to be managed to try and keep your blood chemistry as stable as possible. A person who is a suitable candidate for a kidney donation only has to be on dialysis until a donated kidney becomes available. This can range from a few months for people who have a relative willing to provide a living donation, to around three years for people waiting for a deceased kidney donation to become available. For people who are not suitable for a kidney transplant because of another serious health condition, such as cancer or severe heart disease, will need to be on dialysis for the rest of their lives. Often this is a safer option than a transplant. How do dialysis machines work? A needle linked to a dialysis tube is inserted into a blood vessel. Blood from the body is then passed through a machine containing a partially permeable membrane. On the other side of the membrane is the dialysis fluid. The concentration of the substances allows unwanted ones to move out of the blood and useful ones to stay in!

2. So, you want excess urea and mineral ions to be removed but you don’t want to lose useful mineral ions and glucose. This is controlled by the dialysis fluid. All relies on substances moving along concentration gradients. No active transport! Dialysis is a relatively common type of treatment. Each year, in England, around 5,500 people experience kidney failure and there are currently around 41,000 people receiving treatment for kidney failure. Good vs Bad Can receive dialysis at home instead of having to go to hospital, they are however quite large. It acts as an artificial kidney! And can therefore mean then difference between life and death. You must control your diet and use dialysis a few times a week for a few hours at a time. Dialysis fluid has the same concentration of glucose and mineral ions as normal blood plasma...so NO net movement of these substances from the blood (you don’t want to lose the stuff you need). Salt and urea concentration is low in dialysis fluid...so excess can move ALONG a concentration from blood to fluid. The process of dialysis: