What is Dialysis & How Does it Work?

What is Dialysis?

In many physiological conditions, patients may face failed or damaged kidneys. Individuals with dysfunctional kidneys may have trouble in eliminating body waste and unwanted fluids or water from the blood. Dialysis is a medical process that helps to carry out this important function of kidneys. As such, dialysis is a substitute for the natural function of the kidneys. The process is also known as renal replacement therapy (RRT). The primary function of healthy kidneys is to control the body’s levels of water and minerals at the perfect levels and remove waste. The kidneys also form certain important fluids that are vital in metabolism; dialysis doesn’t have any contribution in this particular functionality.

What is Dialysis & How Does it Work?

How Does Dialysis Work?

There are mainly two types of dialysis that could be done to remove the toxins from the body: Hemodialysis and Peritoneal dialysis. The third type includes hemofiltration which is somewhat similar to hemodialysis. The process in which each type of dialysis work is described below:

  • Hemodialysis: It is the most practiced dialysis process all around the world. Here, an artificial kidney, called hemodialyzer is used to remove waste and electrolytes from the blood. For filtering and purifying the blood in the body, a vascular access is created surgically to pass a maximum quantity of blood into the hemodialyzer. In a long-term dialysis treatment two types of vascular access are developed called Arteriovenous (AV) fistula. In this vascular access, a connection is made among an artery, a vein, and an AV graft. The AV graft is actually a looped tube. In some situations, a catheter may be introduced into the large vein in the neck. The treatment process requires 3-5 hours in one session at least 3 days in a week. The length of the dialysis depends on the quantity of the toxic substance in the body and body size.
  • Peritoneal Dialysis and Its Work Process: In this dialysis process, a catheter is implanted into the abdominal area. For drawing out the waste substances, a special fluid called dialysate is flown into the abdomen. It then draws out the waste substances from the bloodstream through the catheter. Depending on the physical condition of the patient, doctors undertake different types of peritoneal dialysis process. Among them, the following two types are the most popular ones:
    • Continuous Ambulatory Peritoneal Dialysis (CAPD): In the continuous ambulatory peritoneal dialysis process, the abdomen is filled and drained several times a day. In one cycle, the dialysate is left in the abdomen for 8 hours and then drained out. Another quantity of fresh dialysate is again filled in the abdomen immediately. This process is continued for 2-3 times every day.
    • Continuous Cycler-assisted Peritoneal Dialysis (CCPD): In the continuous cycler-assisted peritoneal dialysis process, a special machine is used to cycle the dialysate fluid in and out of the abdomen. This process is normally performed at night when the patient sleeps.

What are the Components Required for Dialysis?

As discussed before, below are the essential components of dialysis:

  • Dialysis Fluid: In all types of dialysis process, the dialysis fluid helps to remove the waste products from the blood. Besides, it comprises of a range of ingredients that help to correct imbalances in the body fluid that may occur due to kidney failure.
  • Semipermeable Membrane: In dialysis, a semipermeable membrane is required that splits up the blood from the fluid used for dialysis. This semipermeable membrane permits some specific substances to pass through, but not all fluids. It helps to clean waste substances, electrolytes, water, and other substances to be removed from the blood into the dialysis fluid through diffusion. The diffusion process solely depends on the permeability of the membrane, and the molecular structure of the substances in the process, nature of the dialysis fluid, and the supply of blood.
  • Blood Supply: Efficiency of the dialysis treatment vastly depends on the blood supply to the membrane.
  • Fluid Removal: A different process of fluid removal is undertaken in hemodialysis and peritoneal dialysis. In the process of hemodialysis, the dialysis machine creates pressure to pull fluid from the blood through the semipermeable membrane. In peritoneal dialysis process glucose is used as one of the ingredients in the dialysis fluid. It helps in removing excess fluid from the blood keeping a balance of different fluid ingredients in the body as a whole.


Dialysis is immensely helpful to stay fit when the kidneys fail to perform normally. However, it can’t be a replacement for the kidneys. Patients who take dialysis on a regular basis need to follow a strict drinking and eating habit along with the medications as prescribed by the doctors. If there is no other illness detected, a patient taking dialysis can lead a normal life and travel anywhere but the dialysis treatment is to be continued as per the schedule.

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Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:March 8, 2019

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