Renal Dialysis

Healthy kidneys regulate the body's internal environment of water and salts and excrete the end products of the body's metabolic activities and excess water (as urine). They also produce and release into the bloodstream hormones that regulate vital functions including blood pressure, red blood cell production, and calcium and phosphorus metabolism.

Impaired kidney function may affect any or all of these processes and may be due to problems in the kidney, a disease in other organs, or caused by the normal, age-related processes. It may be acute or chronic and either minor or life-threatening. All of these distinctions are important determinants of prognosis and appropriate treatment. When a person's loss of kidney function is so severe as to be incompatible with life, the person is said to be in renal failure--renal meaning pertaining to the kidneys.

Acute renal failure -- is the sudden, potentially reversible loss of kidney failure. It may be caused by any of several diseases, by drugs that are toxic to the kidneys, surgery, trauma, reduction or cessation of blood flow (i.e., ischemia) to the kidneys, or by obstruction of urine flow. Many persons in acute renal failure regain natural function of the kidney after temporary support by dialysis. Others die from the underlying disorder that caused the kidney to fail or the problem may lead to chronic renal failure.

Chronic renal failure -- is irreversible, often progressive loss of kidney function. It can be caused by any of a large number of known and unknown factors, including immunological, congenital, or infectious diseases, or trauma to the kidneys. By far the most common cause among elderly dialysis patients in Medicare's ESRD (End-stage renal disease) program is hypertension (with heart and renal diseases). Other less common causes in elderly people are glomerulonephritis, diabetic nephropathy, polycystic kidney disease, and pyelonephritis.

As defined by Medicare regulations, ESRD is the "stage in chronic renal impairment that appears irreversible and permanent, and requires a regular course of dialysis or kidney transplantation to maintain life." ESRD, with an accompanying syndrome called uremia (i.e., the symptomatic phase of renal failure), affects almost every system of the body, including the cardiovascular, respiratory, endocrine, central and peripheral nervous systems, the gastrointestinal tract, blood cells, skin, and bones. The symptoms often are so general that a diagnosis of kidney disease may not be clear. The scientific understanding of kidney disorders is limited.

Disordered kidney function may be detected by simple laboratory tests such as urinalysis, measurement of blood chemistries (urea, creatinine, electrolytes, calcium, and phosphorus), and by determining the kidney's ability to clear standard substances from the blood.

Treatment

ESRD can be managed by renal dialysis or reversed by a successful kidney transplant from a living or cadaveric donor. In special cases, other newer technologies such as hemoperfusion, hemofiltration, hemodiafiltration, and plasmapheresis may be used.

Kidney transplantation -- is the preferred treatment for some persons. A successful kidney transplant can restore an individual to good health and a nearly normal lifestyle. The best results are obtained when the organ donor is a living, related donor, although good success is also achieved with cadaver kidneys. Unfortunately, while transplantation is an attractive solution in principle, there are many difficulties in its implementation, especially the severe shortage of appropriately matched donor kidneys. In addition, life-long immunosuppressive therapy, necessary to prevent rejection of the donor organ, has many deleterious effects.

Because of these and other problems, kidney transplantation is not at present a realistic option for most ESRD patients. Due to additional problems that are age-related such as those with multiple illnesses, vascular diseases (e.g., arteriosclerosis), and decreases in immune function kidney transplants are seldom performed in older people. So, renal dialysis is the only widely used ESRD treatment for the elderly.

Renal dialysis -- is an artificial method of maintaining the chemical balance of the blood when the kidneys have failed. The term dialysis refers to the process in which the components of the blood are separated using a semipermeable membrane. The blood is cleansed of impurities, either by cycling the blood through a machine, containing a membrane, and back into the patient via catheters (hemodialysis), or by cycling dialyzing fluid into and out of the abdomen using the patient's peritoneal membrane as a filter (peritoneal dialysis).

The effectiveness of dialysis depends on both its duration and efficiency. Two main types of dialysis are available:

hemodialysis, and

peritoneal dialysis (including several variants).

Hemodialysis -- is a process involving pumping the blood out of a individual's body into a dialyzer where impurities are removed, then returning the blood to the individual's body. Dialyzers consist of three parts: a compartment for the blood, a compartment for the dialysate, and a semipermeable membrane separating the two. For most ESRD patients using hemodialysis, treatments are carried out three times weekly for a duration of 3 to 5 hours each time.

Peritoneal dialysis -- is a process that uses the individual's peritoneum (the semipermeable membrane surrounding the abdominal organs and lining of the abdominal cavity) to perform dialysis inside the patient's body. Sterile, warmed dialysis fluid is infused via a catheter into the patient's peritoneal cavity, allowed to remain there the prescribed length of time, then drained out along with the dissolved waste products, discarded, and replaced with fresh fluid.

Depending on the locale and timing of the procedure, chronic peritoneal dialysis may be intermittent (IPD); continuous cycling (CCPD); or continuous ambulatory (CAPD). CAPD, is a portable self-dialysis technique that affords individuals relative freedom and control over their own care, because it requires no machine and, often, no assistance. In this procedure, dialysis fluid of approximately 2 liters from a sealed bag is first emptied into the peritoneal cavity through a catheter. The empty bag is stowed in a pouch higher than the abdomen while the patient walks around, and finally the bag is hung below the abdomen to drain out the used fluid. The old bag is then changed for a new one.

The effectiveness of the dialysis depends on both its duration and efficiency. Survival rates among chronic dialysis patients are related to: age at the time of starting treatments, cause of renal disease, and presence of preexisting disease at the time of starting dialysis. In some cases, a point may be reached where dialysis appears to be of no further medical benefit, where an individual does not wish to continue, or when a surrogate decision is needed. This point may come in a matter of weeks of after many years of dialysis treatment.

Last update 7/21/96

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