THE kidneys’ primary function is to filter blood to get rid of waste products, toxins and excess water and electrolytes from the body, whilst reabsorbing useful chemicals. Many medicines are also excreted by the kidneys. The kidneys help in the regulation of the blood pressure and also produce hormones that help regulate the production of red blood cells and the growth and maintenance of bones.
The kidneys enable a person to consume various food, medicines, fluids and substances without toxic by-products reaching levels harmful to the body.
The functions of both kidneys can be performed sufficiently by one kidney.
Vital process: In haemodialysis, blood is transferred into a machine that removes waste products and excess fluids. The filtered blood is then passed back into the body.
Kidney (renal) failure occurs when they are unable to perform its functions, leading to accumulation of toxic substances in the body and consequent harm to health.
Renal failure can be acute or chronic. The former occurs rapidly and the latter, gradually over many years, during which the kidneys are destroyed slowly.
When the kidneys fail, their function has to be replaced by dialysis or kidney transplantation. The latter is the preferred treatment but is not done often enough because there are insufficient donors and some patients are not suitable candidates for transplantation. As such, the survival of many patients is dependent on dialysis.
According to the 16th report of the Malaysian Transplant and Dialysis Registry 2008, the number of new dialysis patients increased from 1,559 in 1999 to 3,874 in 2007, i.e. 69 and 143 per million population respectively. The number of patients undergoing dialysis increased from 5,542 (244 per million population) in 1999 to 17,015 (626 per million) in 2007 and almost 19,000 in 2008.
Funding for new dialysis treatment was provided by the Government in about 54% of new cases, non-governmental organisations in about 10% and self funding in about 25%.
Diabetic patients accounted for about 55% of new dialysis patients. There are two types of dialysis i.e. haemodialysis and peritoneal dialysis.
Haemodialysis
The body’s waste products are removed by inserting a needle into a connection between an artery and a vein (arterio-venous shunt), which is done through a minor surgical procedure. The needle, which is attached by a tube to a dialysis machine, permits the transfer of blood into the machine, which removes waste products and excess fluids. The filtered blood is then passed back into the body.
The dialysis machine has two sections, one for the patient’s blood, and another for a fluid called a dialysate, separated by a thin membrane. The membrane permits waste products and excess fluids to pass through whilst retaining blood cells and proteins in the blood.
Haemodialysis is usually done thrice a week, with each session lasting four to five hours. The appropriate amount of dialysis helps to maintain the patient’s health. Regular laboratory investigations are necessary to ensure the adequacy of the dialysis. There are reports of better survival with short daily dialysis when compared with the conventional regime. However, this requires more resources than are available.
Haemodialysis is carried out in hospitals, dialysis centres, and even at home, if one can afford it.
Peritoneal dialysis
The peritoneum is a thin membrane lining the abdominal cavity with its organs like the liver, gall bladder, gut, female reproductive tract, etc. There are numerous tiny blood vessels in the peritoneum, making it suitable for filtering blood.
A small incision is made in the abdomen, and a catheter, which is a small flexible tube, is inserted into the peritoneal cavity, which is the space lined by the peritoneum. The dialysate is then allowed to flow into and out of the abdominal cavity for a specified period of time, during which the abdomen may feel fuller than usual.
With the movement of blood through the blood vessels of the peritoneum, waste products and excess fluid move out of the blood and into the dialysate, which is removed from the abdominal cavity at the end of the dialysis.
There are two main schedules of peritoneal dialysis, i.e. continuous ambulatory peritoneal dialysis (CAPD) and continuous cycling peritoneal dialysis (CCPD).
CAPD involves filling the abdominal cavity with dialysate, leaving it in the abdominal cavity, and later draining away the dialysate through the effect of gravity. Three or four exchanges are needed during the day and one during sleep. One is free to carry out daily activities during the time the dialysate is in the abdominal cavity.
CCPD involves a device called a cycler, which automatically fills the abdominal cavity with dialysate three to five times at night, allowing the dialysate to remain in the abdominal cavity and then draining it away into a sterile bag which is emptied in the morning.
Although attached to the cycler for 10 to 12 hours at night, the patient is not connected to the device during the day, thereby allowing greater flexibility with activities during the day.
The choice of CAPD or CCPD is influenced by the patient’s medical condition, lifestyle and personal preferences. Some people use a combination of both methods to customise their dialysis programme.
Peritoneal dialysis is different from haemodialysis. The former can be done at work or home. It is more suitable for patients who cannot tolerate the changes in the fluid balance in haemodialysis. In addition, the need for medicines and diet restriction may be less as compared to haemodialysis.
Not everyone with renal failure is a suitable candidate for peritoneal dialysis. One requires manual dexterity or a reliable caregiver and the ability to care for oneself at home. It is unsuitable for patients who have extensive surgical scars in the abdomen or who suffer from inflammatory bowel disease.
In deciding on the mode of dialysis, the factors that have to be considered include the general health status of the patient, the functional state of the kidneys, the situation at home, personal preferences and financing.
Side-effects
There are side-effects with both haemodialysis and peritoneal dialysis. This is due to the manner in which the dialysis is carried out and the fact that dialysis cannot totally compensate for the loss of kidney function.
The side-effects of haemodialysis include:
> Low blood pressure is common and is due to the decrease in the body’s fluid content during the dialysis process.
> Muscle cramps, usually in the legs, may occur in some patients during the dialysis process. It has been attributed to the muscles’ reaction to fluid loss that occurs during dialysis.
> Itchy skin is experienced by many patients. It is thought to be due to an increase of potassium in the body.
The side-effects of peritoneal dialysis include:
> Infections – The most common infection is peritonitis, which is an infection of the lining of the abdominal cavity. This arises when the equipment used is not sterilised properly. The site of insertion of the catheter is another site of infection. All infections have to be treated.
If untreated or inadequately treated, peritonitis can be life-threatening. Infections can be prevented by strict adherence to the instructions given by the doctor and/or nurse.
> Hernia – This is a weakness in the muscle through which an internal part of the body pushes through. It arises because the presence of the dialysate inside the abdominal cavity for several hours places a strain on the abdominal muscles.
> Weight gain is due to the absorption of the sugar present in the dialysate, resulting in an increase in calorie intake by the body.
Conclusions
The success of dialysis depends on the patient’s age, the causes of the kidney failure, and whether there are other medical conditions like diabetes and/or heart disease.
Teamwork and co-operation with the attending doctors and nurses are essential to optimise the benefits of dialysis.
It is important to remember that dialysis is not a cure for chronic renal failure. It can only compensate for the loss of kidney function to a certain extent. Once a patient with chronic renal failure is on dialysis, he or she has to continue on it throughout life unless he or she gets a kidney transplant.
Dr Milton Lum is a member of the board of Medical Defence Malaysia. This article is not intended to replace, dictate or define evaluation by a qualified doctor. The views expressed do not represent that of any organisation the writer is associated with.
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