Dialysis is the artificial process of eliminating waste (diffusion) and unwanted water (ultrafiltration) from the blood. Our kidneys do this naturally. Some people, however, may have failed or damaged kidneys which cannot carry out the function properly - they may need dialysis.
Why is kidney dialysis necessary?
Approximately 1,500 liters of blood are filtered by a healthy person's kidneys each day. We could not live if waste products were not removed from our kidneys. People whose kidneys either do not work properly or not at all experience a buildup of waste in their blood. Without dialysis the amount of waste products in the blood would increase and eventually reach levels that would cause coma and death.
Dialysis is also used to rapidly remove toxins or drugs from the blood.
There are two main types of dialysis - hemodialysis and peritoneal dialysis
What type of dialysis a patient should have really does depend on each individual case. Studies have indicated clearly that for kidney disease patients who need to undergo dialysis, one type of treatment is not best for all.
Hemodialysis
The blood circulates outside the body of the patient - it goes through a machine that has special filters. The blood comes out of the patient through a catheter (a flexible tube) that is inserted into the vein. The filters do what the kidney's do; they filter out the waste products from the blood. The filtered blood then returns to the patient via another catheter. The patient is, in effect, connected to a kind of artificial kidney.
Patients need to be prepared for hemodialysis. A blood vessel, usually in the arm, needs to be enlarged. Surgery is required for this. The enlarged vein makes the insertion of the catheters possible.
Hemodialysis usually lasts about 3 to 4 hours each week. The duration of each session depends on how well the patient's kidneys work, and how much fluid weight the patient has gained between treatments.
The following people may have hemodialysis done at home:
- People who can and want to learn how to do it at home.
- People who are willing to carry on doing it at home.
- People whose condition has been stable while on dialysis.
- People who do not suffer from other diseases which would make home hemodialysis unsafe.
- People who have suitable blood vessels for the insertion of the catheters.
- People who have a caregiver, and that caregiver is willing to help with hemodialysis. People whose homes can be adapted for hemodialysis equipment.
Peritoneal dialysis
A sterile (dialysate) solution rich in minerals and glucose is run through a tube into the peritoneal cavity, the abdominal body cavity around the intestine, where the peritoneal membrane acts as a semi-permeable membrane.
The abdomen is the area between the chest and hips - it contains the stomach, small intestine, large intestine, liver, gallbladder, pancreas and spleen. Peritoneal dialysis uses the natural filtering ability of the peritoneum - the internal lining of the abdomen. In other words, peritoneal dialysis uses the lining of the abdomen as a filter of waste products from the blood.
The dialysate is left there 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 generally repeated several times during the day - with an automated system it is often done overnight. The elimination of unwanted water (ultrafiltration) occurs through osmosis - as the dialysis solution has a high concentration of glucose, it results in osmotic pressure which causes the fluid to move from the blood into the dialysate. Consequently, a larger quantity of fluid is drained than introduced.
Although peritoneal dialysis is not as efficient as hemodialysis, it is carried out for longer periods. The net effect in terms of total waste product and salt and water removal is about the same as hemodialysis.
Peritoneal dialysis is done at home by the patient; by a willing and motivated patient. It gives the patient a greater amount of freedom and independence because he/she does not have to come in to the clinic at multiple times each week. It can also be done while traveling with a minimum of specialized equipment. Peritoneal dialysis is said to'save lives and save money'.
Before having peritoneal dialysis, the patient needs to have a small surgical procedure to insert a catheter into the abdomen. This is kept closed off, except when fluid is being introduced or taken out of the abdomen.
There are two principal types of peritoneal dialysis:
- Continuous ambulatory peritoneal dialysis (CAPD) - this requires no machinery and can be done by the patient or a caregiver. The dialysate is left in the abdomen for up to eight hours. It is then replaced with a fresh solution straight away. This happens every day, about four to five times per day.
- Continuous cyclic peritoneal dialysis (CCPD) - a machine does the dialysis fluid exchanges. It is generally done during the night while the patient sleeps. This needs to be done every night. Each session lasts from ten to twelve hours. After spending the night attached to the machine, the majority of people keep fluid inside their abdomen during the day. Some patients may require another exchange during the day. A study found that a significant number of patients prefer "dialysis while you sleep" treatment. Nocturnal dialysis improves heart disease in patients with end-stage kidney failure.
Peritoneal is ideal for patients who may find hemodialysis too exhausting, such as elderly people, babies and children. As it can be done while the patient is traveling it is more convenient for those who have to go to school or to work.
Kidney failure symptoms
Kidney failure tends to happen gradually. Even if just one kidney works, or both work partially, normal kidney function is still possible. So, it can be a very long time before any symptoms are noticed by the patient. When symptoms do occur they tend to be different from person-to-person, making it harder for doctors to diagnose kidney failure quickly. The following symptoms may be present:
- Fatigue (tiredness)
- Frequent need to urinate, especially at night. Frequency grows with time
- Itchy skin
- Erectile dysfunction (men have difficulty getting and/or sustaining an erection)
- Nausea
- Shortness of breath
- Water retention (swollen feet, hands, ankles)
- Blood in urine
- Protein in urine
A sudden injury can cause kidney failure. When it does, symptoms tend to appear faster, and progress more rapidly as well.
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