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Dialysis, more correctly known as renal (kidney) dialysis is the process of artificially performing the functions of the kidneys to filter out toxic waste substances and balance the water and electrolyte levels in the blood and other body fluids. Renal dialysis is only considered when end-stage kidney failure reaches a point where the kidneys are unable to perform this function.
Usually one kidney can manage with a low level of functioning and a healthy kidney can compensate for even a total failure of the other kidney. In severe cases where both kidneys fail, dialysis is necessary. Sometimes in acute kidney failure, dialysis is needed in the short term until the underlying disease is treated and at least partial kidney function is restored.
When is dialysis needed?
Indications for Dialysis
The kidneys play several important roles in the body either directly or indirectly. By controlling the composition of the urine and the amount of urine passed out it can alter the water and electrolyte levels. This can impact on the blood volume and blood pressure. It also filters out toxic waste products be it the byproducts of metabolism or that of drug and alcohol consumption. When the kidneys are diseased to the extent that it cannot function effectively enough to maintain life supporting functions, then renal replacement therapy is needed as soon as possible. The two types of renal replacement therapies are renal dialysis or kidney transplantation. The latter is not a simple undertaking for various reasons although it is the preferred option. Renal dialysis is then the only option.
Dialysis needs to be commenced once the kidney function decreases to 10% to 15% of its normal levels. It should ideally be started before this but any further deterioration beyond these levels will lead to death. Kidney function may be compromised with acute or chronic kidney failure. Acute renal failure which may arise with a heart attack will only require temporary dialysis (short term). Chronic renal failure occurs with long term hypertension (high blood pressure), diabetes mellitus, flmerulonephritis or polycystic kidney disease. It eventually leads to end-stage renal disease (ESRD) which is irreversible. If a transplant cannot be conducted, dialysis has to be continued indefinitely.
The most effective way of monitoring declining kidney function is by assessing the levels of the serum creatinine and the blood urea nitrogen (BUN). Dialysis is usually commenced once the creatinine clearance, meaning the difference between the levels of creatinine in the blood and urine, drops to 10cc to 12cc per minute. Certain clinical features may also be an indicator to commence with dialysis irrespective of the creatinine clearance readings. These symptoms include :
- Excessive fluid retention
- Ankle swelling
- Difficulty breathing
- Very high blood pressure
- Nausea
- Vomiting
- Poor mental status
What are the different types of dialysis?
Methods for Dialysis
There are two methods of dialysis – hemodialysis and peritoneal dialysis. These methods may differ in the type of filtration method but both essentially take over the functioning of the incompetent kidneys.
- Hemodialysis is where toxins, wastes, electrolytes and excess water are mechanically from the blood with a dialysis machine utilizing a type of filter called the dialyzer.
- Peritoneal dialysis is where toxins, wastes, electrolytes and excess water are filtered from the blood through the inner abdominal lining known as the peritoneal membrane.
There are benefits and risks of each method and the doctor will have to decide along with the patient as to the most suitable option for the individual.
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