People with failed or damaged kidneys may have difficulty eliminating waste and unwanted water from the blood. Dialysis is an artificial way of carrying out this process.
Dialysis substitutes the natural work of the kidneys, so it is also known as renal replacement therapy (RRT).
Healthy kidneys regulate the body’s levels of water and minerals and remove waste.
The kidneys also secrete certain products that are important in metabolism, but dialysis cannot do this.
A person who has lost 85 to 90 percent of their kidney function will be a likely candidate for dialysis. Around 14 percent of the population of the United States are thought to have chronic kidney disease (CKD).
What is dialysis?
Dialysis can carry out the function of the kidneys if the kidneys no longer work effectively.
A healthy person’s kidneys filter around 120 to 150 quarts of blood each day. If the kidneys are not working correctly, waste builds up in the blood. Eventually, this can lead to coma and death.
The cause might be a chronic, or long-term condition, or an acute problem, such as an injury or a short-term illness that affects the kidneys.
Dialysis prevents the waste products in the blood from reaching hazardous levels. It can also remove toxins or drugs from the blood in an emergency setting.
The kidneys are crucial for eliminating waste, and other functions.
In hemodialysis, the blood circulates outside the body. It goes through a machine with special filters.
The blood comes out of the patient through a flexible tube known as a catheter. The tube is inserted into the vein.
Like the kidneys, the filters remove the waste products from the blood. The filtered blood then returns to the patient through another catheter. The system works like an artificial kidney.
Those who are going to have hemodialysis need surgery to enlarge a blood vessel, usually in the arm. Enlarging the vein makes it possible to insert the catheters.
Hemodialysis is usually done three times a week, for 3 to 4 hours a day, depending on how well the kidneys work, and how much fluid weight they have gained between treatments.
Hemodialysis can be done in a special dialysis center in a hospital or at home.
People who have dialysis at home, or their caregiver, must know exactly what to do.
If a person does not feel confident doing dialysis at home, they should attend sessions at the hospital.
Home hemodialysis is suitable for people who:
have been in a stable condition while on dialysis
do not have other diseases that would make home hemodialysis unsafe
have suitable blood vessels for inserting the catheters
have a caregiver who is willing to help with hemodialysis
The home environment must also be suitable for taking hemodialysis equipment.
Symptoms, causes, and treatment of chronic kidney disease
Find out more about what it means to have chronic kidney disease.
While hemodialysis removes impurities by filtering the blood, peritoneal dialysis works through diffusion.
In peritoneal dialysis, a sterile dialysate solution, rich in minerals and glucose, is run through a tube into the peritoneal cavity, the abdominal body cavity that surrounds the intestine. It has a semi-permeable membrane, the peritoneal membrane.
Peritoneal dialysis uses the natural filtering ability of the peritoneum, the internal lining of the abdomen, to filter waste products from the blood.
The dialysate is left in the peritoneal cavity for some time, so that it can absorb waste products. Then it is drained out through a tube and discarded.
This exchange, or cycle, is normally repeated several times during the day, and it can be done overnight with an automated system.
The elimination of unwanted water, or ultrafiltration, occurs through osmosis. The dialysis solution has a high concentration of glucose, and this causes osmotic pressure. The pressure causes the fluid to move from the blood into the dialysate. As a result, more fluid is drained than is introduced.
Peritoneal dialysis is less efficient than hemodialysis. It takes longer periods, and it removes around the same amount of total waste product, salt, and water as hemodialysis.
However, peritoneal dialysis gives patients more freedom and independence, because it can be done at home instead of going to the clinic several times each week. It can also be done while traveling with a minimum of specialized equipment.