Summary
Highlights
Dialysis is a medical therapy that removes waste products from the blood when a patient's kidneys can no longer perform this function adequately. There are two primary types: hemodialysis and peritoneal dialysis.
In hemodialysis, blood is filtered outside the body using a dialysis machine. Blood is pumped from the patient, cleansed by the machine, and then returned. A minor surgery is performed to create a vascular access (fistula or graft) for regular treatments, or a catheter for emergency access.
Inside the machine, blood flows through tiny tubes surrounded by a dialysis solution called dialysate. The tube walls act as semipermeable membranes, allowing small molecules like water, nitrogenous wastes, and electrolytes to pass through via osmosis and diffusion from higher to lower concentrations. The dialysate is constantly replaced to remove these wastes.
The dialysis fluid can contain substances added for the patient, such as bicarbonate to adjust blood pH, erythropoietin for low production by failing kidneys, and other medications. An anticoagulant like heparin is typically added to prevent blood clotting due to contact with foreign surfaces. A nephrologist prescribes the specific dialysate composition.
Hemodialysis treatments are usually 4 hours long, 3 times a week, performed in a dialysis center. Potential complications include blood infection, thrombosis, and internal bleeding caused by the anticoagulant.
In peritoneal dialysis, dialysis fluid is introduced into the patient’s abdominal cavity via a catheter. The peritoneum, the lining of the abdomen, acts as the natural filtering membrane. The fluid remains in the body for several hours, allowing waste exchange with blood in underlying vessels before being discarded. This therapy can also be performed automatically at night.
Peritoneal dialysis is less effective per session than hemodialysis, but over longer periods, the results are comparable. It offers more flexibility, is better tolerated by patients, and is less expensive. However, it is more frequently complicated by abdominal infections.