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When do patients require dialysis?
Patients usually require dialysis when the waste products in their body become so high that they start to become sick from them. The level of the waste products usually builds up slowly. Doctors measure several blood chemical levels to help decide when dialysis is necessary. The two major blood chemical levels that are measured are the "creatinine level" and the "blood urea nitrogen" (BUN) level. As these two levels rise, they are indicators of the decreasing ability of the kidneys to cleanse the body of waste products.
Doctors use a urine test, the "creatinine clearance," to measure the level of kidney function. The patient saves urine in a special container for one full day. The waste products in the urine and in the blood are estimated by measuring the creatinine. By comparing the blood and urine level of this substance, the doctor has an accurate idea of how well the kidneys are working. This result is called the creatinine clearance. Usually, when the creatinine clearance falls to 10-12 cc/minute, the patient needs dialysis.
The doctor also uses other indicators of the patient's status to decide about the need for dialysis. If the patient is experiencing a major inability to rid the body of excess water, or is complaining of problems with the heart, lungs, or stomach, or difficulties with taste or sensation in their legs, dialysis may be indicated even though the creatinine clearance has not fallen to the 10-12 cc/minute level.
What types of dialysis are there?
There are two main types of dialysis: "hemodialysis" and "peritoneal dialysis." Hemodialysis uses a special type of filter to remove excess waste products and water from the bblood. Peritoneal dialysis uses a fluid that is placed into the patient's abdominal cavity through a special plastic tube to remove excess waste products and fluid from the body.
During hemodialysis, blood passes from the patient's body through a filter in the dialysis machine, called a "dialysis membrane." For this procedure, the patient has a specialized plastic tube placed between an artery and a vein in the arm or leg (called a "gortex graft"). Sometimes, a direct connection is made between an artery and a vein in the arm. This procedure is called a "Cimino fistula." Needles are then placed in the graft or fistula, and blood passes to the dialysis machine, through the filter, and back to the patient. If the patient requires dialysis before a graft or a fistula is placed, a large diameter catheter is placed directly into a large vein in the neck or leg in order to perform dialysis. In the dialysis machine, a solution on the other side of the filter receives the waste products from the patient.
Peritoneal dialysis uses the patients own body tissues inside of the belly (abdominal cavity) to act as the filter. The abdominal cavity is lined with a special membrane, the peritoneal membrane. A plastic tube called a " peritoneal dialysis catheter" is placed through the abdominal wall into the abdominal cavity. A special fluid is then flushed into the abdominal cavity and washes around the intestines. The peritoneal membrane acts as a filter between this fluid and the blood stream. By using different types of solutions, waste products and excess water can be removed from the body through this process.