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What is Dialysis? /Explain Dialysis

The kidneys of the human body are responsible for filtering waste products from the bloodstream. They are located on either side in the back of the abdominal cavity. Dialysis is a process that substitutes many of the normal functions of the kidneys. It can allow individuals to live productive and useful lives, even though their kidneys no longer work adequately. 

An important job of the kidney is to regulate the body's fluid balance. It does this by adjusting the amount of urine that is excreted daily. On hot days, the body sweats and as a result, less water needs to be excreted through the kidneys. On cold days, the body sweats less, so the urine output needs to be greater to maintain the proper balance within the body. It is the kidney's job to regulate fluid balance by adjusting urine output.

Another important function of the kidney is to remove waste products from the body throughout the day. As the body functions, cells use energy. The operation of the cells produces waste products that should be removed from the body. When these waste products are not removed they build up and an elevation of waste products can result in a condition called "azotemia." 

Dialysis definition: Dialysis is a process of removing excess fluid and waste products from the body. It is necessary when the kidneys are not able to adequately filter blood. It allows patients with kidney problems and kidney failure a chance to live productive lives. 

Principle of Dialysis

The basic principles of dialysis go around the diffusion of solutes and ultrafiltration of fluid across a semipermeable membrane. Diffusion is a property of particles in water; they tend to move from an area of high concentration to an area of low concentration. A semipermeable membrane is a thin layer of material that contains pores of various sizes. Fluid and smaller solutes through the membrane, but the membrane blocks the passage of larger substances such as red blood cells and large proteins. This replicates the biological filtering process that occurs in the kidneys when the blood enters the kidneys and the larger substances are separated from the smaller ones in the glomerulus.

Types of Dialysis

There are 3 primary types and 2 secondary types of dialysis. The primary types of dialysis are:

  1. Haemodialysis

In this type of dialysis procedure an external machine and a special type of filter is used to remove excess water and waste products from the blood.

During haemodialysis, blood passes from the patient's body to the dialysis machine through sterile tubing and into a filter that is called a dialysis membrane. The patient has a specialised vascular tube placed between an artery and a vein in the arm or leg which is called a Gortex graft. 

Sometimes, a direct connection is made between an artery and a vein in the arm, this procedure is termed as a Cimino fistula. Needles are placed in the graft or fistula, and blood passes to the dialysis machine, through the filter, and back to the patient.

The patient's blood is pumped through the blood compartment of a dialyser, exposing it to a partially permeable membrane. The dialyser is composed of thousands of tiny hollow synthetic fibres. They make up a wall that acts as the semipermeable membrane. 

During the process, blood flows through the fibres and the dialysis solution flows around the outside of the fibres.  As a result, water and wastes move between these two solutions. The purified blood is then returned via the circuit back to the body. Ultrafiltration occurs by increasing the hydrostatic pressure across the dialyser membrane. It is usually done by applying negative pressure to the dialysate compartment of the dialyser. This pressure gradient causes the water and the dissolved solutes to move from the bloodstream to the dialysate and allows the removal of several litres of excess fluid during a typical 4-hour treatment.

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  1. Peritoneal Dialysis

In the peritoneal dialysis process, a sterile solution containing glucose (also referred to as a  dialysate) is run through a tube into the peritoneal cavity, the abdominal body cavity around the intestine. In this place, the peritoneal membrane acts as a partially permeable membrane.

This dialysis is repeated 4 to 5 times per day, however, this type of dialysis is less efficient than haemodialysis, but because it is carried out for a longer time the net effect in terms of removal of waste products and salt and water are similar to haemodialysis. Peritoneal dialysis can be carried out at home by the patient without help. This means that the patients do not have to visit a dialysis clinic multiple times per week.

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  1. Haemofiltration

Hemofiltration is a similar treatment to haemodialysis, but the principle behind this process is different. The blood is pumped through a dialyser, but no dialysate is used. A pressure gradient is applied that results in excess water moving across the very permeable membrane rapidly. Due to this many dissolved substances, including ones with large molecular weights also move and are cleared. Salts and water lost from the blood due to this process are replaced with a substitution fluid that is infused into the system during the treatment.

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The Two Types of Secondary Dialysis Are

  1. Haemodiafiltration

It combines the dialysis mechanism of haemodialysis and hemofiltration and is used to remove toxins from the blood when the kidneys are not working normally. Haemodiafiltration is also used to treat acute kidney injury.

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  1. Intestinal Dialysis

In this process of dialysis, the diet is supplemented with soluble fibres such as acacia fibre, which is digested by bacteria in the colon. This bacterial growth increases the amount of nitrogen that is eliminated in faecal waste. An alternative approach utilises the ingestion of 1 to 1.5 litres of non-absorbable solutions of polyethylene glycol or mannitol every fourth hour

Advantages of Dialysis

Some of the advantages of dialysis, specifically peritoneal dialysis include:

  • The procedure can be carried out at home

  • It is an easy method and does not need any special equipment or the help of a professional.

  • The equipment is less bulky and easy to travel with.

FAQ (Frequently Asked Questions)

1. What is Meant by Dialysis?

Dialysis Meaning: Dialysis is the process of removing excess fluid and waste products from the body.

2. What is Dialysis and How is it Useful?

Dialysis has been used as a process to remove excess fluid and waste products from the body since the 1940s. Healthy kidneys prevent extra water, waste, and other impurities from accumulating in the body. They also help control blood pressure and regulate the levels of chemical elements in the blood including sodium and potassium levels. 

When they can’t perform these functions due to injury or disease, dialysis can help keep the body running as normally as possible. Without dialysis, waste products will accumulate in the blood, poison the body and damage other organs.

3. What is Artificial Kidney Dialysis?

A special filter called an artificial kidney is used during haemodialysis. It is also referred to as a dialyser which cleans the blood. To get blood into the dialyser, the medical practitioner needs to make an access, or entrance, into your blood vessels. This is done with minor surgery, usually on the arm. Then haemodialysis is carried out (also known as the artificial kidney dialysis process)

4. Explain the Process of Dialysis.

Please refer to the types of dialysis section.