4.6.4 Dialysis

Introduction

When the kidneys fail, they can no longer filter waste products and excess water from the blood. Without treatment, waste products build up and can be fatal. Dialysis is a life-saving treatment that performs the filtering function of the kidneys artificially. This topic explains what dialysis is and the two main types: haemodialysis and peritoneal dialysis.

Definition

Dialysis is a process for removing waste and excess water from the blood. It is used when the kidneys are no longer able to perform this function.

To remove the nitrogenous wastes, the blood of the patient is treated through dialysis.

Main Idea

There are two types of dialysis:

• Haemodialysis
• Peritoneal dialysis

Core Concept

Types of Dialysis

Detailed Explanation

1. Haemodialysis

What it is: In this process, blood is filtered through a machine called a dialyzer (artificial kidney).

What happens:

• First, a catheter is inserted into the vein, usually in the arm.
• The blood flows into the tube and then into the machine called a dialyzer.
• Inside the machine, the blood is pumped over the surface of a dialysis membrane (semi-permeable membrane).
• This separates the patient's blood from the dialysis fluid.
• Urea diffuses out of the blood, across the dialysis membrane, and into the dialysis fluid.
• The dialysis fluid already has sugar and salts in it.
• So, sugars and salts from the blood will not diffuse across into the fluid.
• Urea and other wastes pass into the dialysis fluid.
• The patient's cleaner blood passes back into the other vein of the arm through a second catheter.
• Fresh dialysis fluid enters the machine from one end.
• The used dialysis fluid with waste leaves the machine from the other end.

Simple explanation: Haemodialysis is like an external artificial kidney. Blood is taken out of the body, cleaned in a machine, and returned to the body.

Why this is important:

• It removes waste products (urea, creatinine) from the blood.
• It removes excess water.
• It maintains electrolyte balance.

Where it is done: Hospital or dialysis centre.

How often: Usually 3 times a week, each session lasting 3–5 hours.

2. Peritoneal Dialysis

What it is: In this process, the dialysis fluid is pumped into the peritoneal cavity, which is the space around the gut.

What happens:

• The peritoneum, which lines the peritoneal cavity, functions as the dialysis membrane.
• Dialysis fluid is added to the abdominal cavity through a tube (catheter).
• It is left for several hours before removal.
• Exchange takes place between the dialysis fluid and the tissue fluid in the abdomen.
• Waste products and excess water move from the blood into the dialysis fluid.
• The used dialysis fluid is then drained out.

Simple explanation: Peritoneal dialysis uses the lining of your own abdomen (peritoneum) as a natural filter. Dialysis fluid is put into the abdomen, left there to absorb waste, and then drained out.

Where it is done: Can be performed at home.

How often: Must be done regularly, 3 or 4 times a day.

Advantages:

• Can be done at home.
• More flexible schedule.
• No need for needles.

Disadvantages:

• Risk of infection (peritonitis).
• Requires a catheter in the abdomen.

Comparison of Haemodialysis and Peritoneal Dialysis

Intermediate Level

Dialysis is a process for removing waste and excess water from the blood.

Key points:

• Haemodialysis uses an artificial membrane.
• Peritoneal dialysis uses the peritoneum as a natural membrane.
• Both remove urea and other wastes.
• Both remove excess water.
• Both maintain electrolyte balance.

Important Points

• - Dialysis is a process for removing waste and excess water from the blood.
• - To remove the nitrogenous wastes, the blood of the patient is treated through dialysis.
• - There are two types of dialysis: haemodialysis and peritoneal dialysis.
• - In haemodialysis, a catheter is inserted into the vein, usually in the arm.
• - The blood flows into the tube and then into the machine called a dialyzer.
• - Inside the machine, the blood is pumped over the surface of a dialysis membrane.
• - This separates the patient's blood from the dialysis fluid.
• - Urea diffuses out of the blood, across the dialysis membrane, and into the dialysis fluid.
• - The dialysis fluid already has sugar and salts in it.
• - So, sugars and salts from the blood will not diffuse across into the fluid.
• - Urea and other wastes pass into the dialysis fluid.
• - The patient's cleaner blood passes back into the other vein of the arm through a second catheter.
• - Fresh dialysis fluid enters the machine from one end.
• - The used dialysis fluid with waste leaves the machine from the other end.
• - In peritoneal dialysis, the dialysis fluid is pumped into the peritoneal cavity.
• - The peritoneum, which lines the peritoneal cavity, functions as the dialysis membrane.
• - Dialysis fluid is added to the abdominal cavity through a tube.
• - It is left for several hours before removal.
• - Exchange takes place between the dialysis fluid and the tissue fluid in the abdomen.
• - This type of dialysis can be performed at home.
• - It must be done regularly, 3 or 4 times a day.

Remember

• - Dialysis = process for removing waste and excess water from blood
• - Types = haemodialysis and peritoneal dialysis
• - Haemodialysis = blood pumped through dialyzer
• - Dialysis membrane = semi-permeable membrane
• - Peritoneal dialysis = dialysis fluid in peritoneal cavity
• - Peritoneum = natural dialysis membrane
• - Haemodialysis = hospital, 3 times a week
• - Peritoneal dialysis = home, 3–4 times a day
• - Dialysis = life-saving treatment for kidney failure

Common Mistakes

• 1. Confusing haemodialysis and peritoneal dialysis.
• - Haemodialysis = artificial membrane (dialyzer).
• - Peritoneal dialysis = natural membrane (peritoneum).
• 2. Thinking dialysis cures kidney failure.
• - Dialysis is a treatment, not a cure. It performs the filtering function but does not heal the kidneys.
• 3. Forgetting that peritoneal dialysis can be done at home.
• - Peritoneal dialysis can be performed at home. Haemodialysis is usually done in a hospital or dialysis centre.
• 4. Mixing up the frequency of dialysis.
• - Haemodialysis = 3 times a week.
• - Peritoneal dialysis = 3–4 times a day.
• 5. Believing dialysis is only for older people.
• - Dialysis can be needed at any age.
• 6. Thinking dialysis is painful.
• - Haemodialysis involves needle insertion. Peritoneal dialysis does not require needles.
• 7. Forgetting the role of the dialysis fluid.
• - The dialysis fluid contains sugar and salts to prevent their loss from the blood.

Quick Revision

60-Second Revision

• Dialysis = process for removing waste and excess water from blood
• Types = haemodialysis and peritoneal dialysis
• Haemodialysis = blood pumped through dialyzer; hospital; 3 times a week
• Peritoneal dialysis = dialysis fluid in peritoneal cavity; peritoneum acts as membrane; home; 3–4 times a day
• Dialysis membrane = semi-permeable
• Dialysis fluid = contains sugar and salts
• Dialysis = life-saving treatment for kidney failure
• Warning: Dialysis does not cure kidney failure; it only performs the filtering function.