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how does dialysis work

Dialysis is a treatment that takes over some of the kidneys’ job by removing extra fluid and waste products from the blood when the kidneys can no longer do this effectively. It keeps the body’s internal environment more stable and can be used short term (acute kidney injury) or long term (chronic kidney failure), and sometimes as a bridge to kidney transplant.

What dialysis does

  • Removes waste products (like urea and creatinine) that build up when kidneys fail.
  • Removes extra water and helps keep salts (electrolytes) in balance.
  • Helps control blood pressure and reduce symptoms such as swelling, nausea, and fatigue.

Two main types

  • Hemodialysis : Blood is taken out of the body, cleaned by a machine, and returned to the body.
  • Peritoneal dialysis : The lining of the abdomen (peritoneum) is used as a natural filter with special dialysis fluid in the belly.

How hemodialysis works

  • Access to the bloodstream is created, usually by surgically joining an artery and a vein in the arm (arteriovenous fistula) or using a graft or catheter.
  • During treatment, blood flows through tubing into a machine containing a dialyzer (“artificial kidney”), where it passes through tiny hollow fibers separated from a cleansing fluid (dialysate) by a semi‑permeable membrane.
  • Waste products and excess water move from the blood into the dialysate, which is discarded; the cleaned blood is returned to the body.

Typical schedule: about 3 sessions per week, each roughly 3–5 hours, often done in a dialysis center but sometimes at home with training.

How peritoneal dialysis works

  • A soft tube (catheter) is placed into the abdomen a couple of weeks before starting treatment.
  • Special dialysis fluid (dialysate) is run through the catheter into the abdominal cavity, where the peritoneal membrane acts as the filter between blood vessels and the fluid.
  • Over a few hours, waste products and extra water move from the blood into the fluid; then the fluid is drained out and replaced with fresh fluid (“an exchange”).

Two common formats:

  • Manual exchanges during the day (continuous ambulatory peritoneal dialysis, CAPD).
  • Automated peritoneal dialysis (APD) using a cycler machine, often done overnight while sleeping.

When and why dialysis is needed

  • Usually started in advanced chronic kidney disease (often called stage 5 or end‑stage kidney disease) when symptoms are significant or lab results show dangerous buildup of toxins or fluid.
  • Can be used temporarily in severe, sudden kidney failure (for example in critical illness) until kidney function recovers or a longer‑term plan is made.

Living with dialysis

  • Many people on dialysis can work, travel (with planning), and maintain family and social roles.
  • Treatment choices (hemodialysis in‑center vs at home, or peritoneal dialysis) depend on medical factors, lifestyle, home situation, and personal preference, and are best decided with a kidney specialist (nephrologist).

Important : This is general information and not medical advice. Decisions about starting or changing dialysis should always be made with a healthcare professional who knows the specific medical situation.