Dialysis is a medical treatment that replaces some kidney functions by cleaning the blood and removing extra fluid when the kidneys can’t do so adequately. It works primarily through diffusion and ultrafiltration across a semipermeable barrier, using a specially prepared fluid called dialysate. Key ideas
- Why dialysis is needed
- When kidney function declines, waste products (like urea and creatinine) and excess fluids can build up in the blood, leading to symptoms and complications. Dialysis serves as a surrogate kidney, performing filtration and waste removal to maintain chemical balance. This is the core purpose across most dialysis approaches.
- The basic principle
- Blood flows on one side of a semipermeable membrane; dialysate flows on the other side. The dialysate contains water and dissolved substances at carefully chosen concentrations. Because of diffusion, small waste molecules move from higher to lower concentrations (blood to dialysate). Ultrafiltration moves excess fluid out of the blood across the membrane due to hydrostatic pressure differences.
- Main types of dialysis
- Hemodialysis: Blood is pumped out of the body to a machine with a dialyzer (artificial kidney) where it passes through hollow fibers or a membrane. Dialysate flows in the opposite direction to maximize solute exchange. The cleaned blood returns to the body. Sessions typically last about 3–5 hours and occur several times per week.
* Peritoneal dialysis: The peritoneum (the lining of the abdomen) acts as the natural membrane. Dialysate is infused into the abdomen and, after a dwell time, drained, removing wastes and fluid from the blood through peritoneal membrane exchange.
- What is dialysate?
- Dialysate is a specially formulated fluid that helps draw wastes and extra fluid from the blood while maintaining electrolyte balance. Its composition is tailored to mimic normal blood levels for minerals like potassium and calcium, with bicarbonate or a similar buffer to help correct metabolic acidosis.
- Typical experiences and considerations
- Hemodialysis requires vascular access (such as a fistula, graft, or catheter) to reach the bloodstream. Treatments are often done in hospitals, dialysis centers, or at home with proper training. Diet and fluid restrictions are commonly part of ongoing management.
* Peritoneal dialysis provides more home-based flexibility but requires a clean technique to prevent infection and ongoing attention to the peritoneal cavity.
- Outcomes and goals
- Dialysis does not cure kidney disease but replaces enough kidney function to keep people alive and in better health, enabling removal of wastes, balancing minerals, and controlling fluid status. Ongoing medical care guides the choice between hemodialysis and peritoneal dialysis and tailoring of treatment to each individual.
If you’d like, I can tailor this to a specific situation (e.g., differences between in-center and home dialysis, how a typical session goes step by step, or how to prepare for a first dialysis appointment).
