Peritoneal dialysis is one of the two processes used to remove waste products that build up in the blood when the kidneys are not able to do so on their own.
Though known since the 1940s, peritoneal dialysis became a standard treatment used in removing waste products from the body in 1976. An estimated 260,000 people in United States suffer from chronic renal (kidney) failure, and 50,000 die each year from conditions secondary to this disease. The human and financial cost of kidney disease is incalculable, but very expensive. Eighty percent of the financial cost of kidney disease treatment is now provided by the federal government.
On average, approximately one-fifth of the total blood supply of the human body—1.3 qt (1.2 l) of blood—passes through the kidneys every minute. Twelve times every hour, the entire amount of blood present in the body circulates through the kidneys. Through an osmotic process called glomerular filtration, selective fluids and dissolved chemicals are filtered out, but necessary nutrients such as proteins are retained. The filtered-out solution enters a part of the kidney called Bowman's capsule, then passes through a system of tubes that reabsorb nearly all (99%) of the fluid. The remaining 1% that contains the waste products is sent down through two slender tubes, called ureters, to the bladder. From the bladder, the urine created in the kidneys, on average, 1.6 qt (l.5 l), is excreted.
When the kidneys become unable to carry this workload regulation of fluid balance in the body—the kidney's most important function—becomes ineffective or ceases completely. This is called renal failure. Renal failure can be either acute or chronic. Acute renal failure occurs when there is a sudden reduction in kidney function that results in nitrogenous wastes accumulating in the blood. The chief causes are:
- severe blood loss resulting in an insufficient blood supply
- insuffient fluid present in the body due to dehydration
- blockage of blood vessels due to injury
- decline in the heart's pumping ability, such as in heart failure
- low blood pressure leading to shock
- liver failure
- allergic reactions to potentially toxic chemicals
- blocked arteries or veins within the kidneys
- crystals, proteins, or other substances in the kidneys
Chronic renal failure is long term and permanent. The chief causes are:
- high blood pressure
- obstruction of the urinary tract
- abnormalities of the kidneys, such as polycystic kidney disease
- diabetes mellitus
- autoimmune disorders such as lupus erythematosus
The purpose of peritoneal dialysis is to remove the wastes, such as urea and creatinine, that build up in the blood when the kidneys are unable function properly. Peritoneal dialysis attempts to keep fluid and electrolytes (vital chemicals within the body) in proper proportions. Frequently for people with acute renal failure, dialysis may be a temporary measure, used until the kidneys regain their normal function. But though chronic renal failure does not always show symptoms in its earliest
stages, depending upon its severity, it is a progressively more serious condition that will eventually result in death unless a kidney transplant is performed.
The decision to begin dialysis is often based upon the presence of any or all of the following medical conditions resulting from impaired kidney function:
- Uremic encephalopathy: abnormal functioning of the brain.
- Pericarditis: inflammation of the sac surrounding the heart.
- High acidity of the blood that is unresponsive to other medical treatments.
- Heart failure.
- Hyperkalemia: high blood concentrations of potassium that can cause irregular heart beat and even cardiac arrest.
Diet is of special importance for people undergoing dialysis. Their appetites are often poor due to their illness, and proteins are lost during peritoneal dialysis. This makes increasing the protein in their diets very necessary, but patients often have difficulty eating adequate amounts. Sodium and potassium must be restricted to less than 0.12 oz (4 g) of each per day, and phosphorus may also be limited. Fluid retention is monitored by weighing the person regularly, but fluids are not usually restricted unless the concentration of sodium in the blood is steadily decreasing or already very low. Contraindications to the use of peritoneal dialysis would be recent abdominal wounds or infection, or a newly-installed artificial blood vessel graft such as might be placed in repairing a ruptured aorta.
There are two methods of dialysis, hemodialysis and peritoneal dialysis. In hemodialysis the blood is pumped out of the body and through an artificial kidney machine. The purified blood is then returned to the body. In peritoneal dialysis, the mucous membrane that surrounds abdominal organs (the peritoneum) is used as a natural filter. A soft catheter is either surgically inserted into the abdomen and implanted in the peritoneum, or is put in place each time a treatment is done. A sterile cleansing fluid called a dialysate is put into the peritoneum through the catheter. Body wastes then are removed as this dialysate is washed in and out of the abdomen. Each of these peritoneal fluid cycles are called an exchange.
Peritoneal dialysis is usually done at a medical facility called a dialysis center, and can be done in two different ways: continuous ambulatory peritoneal dialysis (CAPD) or continuous cycling peritoneal dialysis (CCPD).
Continuous ambulatory peritoneal dialysis
Either the patient or healthcare provider at the center hangs a sterile plastic bag containing approximately 2 qt (1.8 l) of the dialysate solution. This plastic bag is then placed above shoulder level, causing the fluid in the bag to enter the abdomen slowly. The fluid is then left in the abdomen for four or five hours during which time extra
Continuous cycling peritoneal dialysis
CCPD puts the same amount of fluid into the peritoneum, but it is done by a machine called a cycler. CCPD treatments are usually carried out while the person sleeps, and take about an hour and a half for each sequence that repeats throughout the night.
Preparation for peritoneal dialysis includes a thorough explanation of what is to be done and why. This is particularly important for the patient just beginning treatments. Most patients are eventually taught how to do their own dialysis if they are mentally alert and physically able to do so.
Monitoring of weight, vital signs, and chemicals in the blood will all be done following treatments to assess the person's physical status and the effectiveness of the treatment.
Complications, though not considered common with this procedure, are possible. They include:
- bleeding from the site where the catheter is inserted or within the abdomen
- perforation of abdominal organs by the catheter during placement
- fluid flow blockage caused by blood clots
- infections at the site of catheter insertion (these can sometimes result in the formation of an abscess)
- an abnormally low blood albumin
- development of scar tissue within the peritoneum that can result in partial intestinal obstruction
- hernias of the abdomen or groin (occur in approximately 10% of all patients undergoing peritoneal dialysis)
- very low thyroid hormone levels
- high blood sugar, especially in diabetic patients
- hyperlipidemia, or excessive levels of certain fatty compounds in the blood
The desired results from peritoneal dialysis include removal of adequate quantities of the body's waste products. The patient can then continue to live as comfortably and independently as possible until the kidney condition either resolves itself or a kidney transplant is performed.
Health care team roles
- Renal specialists are responsible for the decision to begin peritoneal dialysis treatments based upon the person's condition. A surgeon would insert a permanent catheter for this treatment.
- Both registered nurses (RNs) and licensed practical nurses (LPNs) will be involved in the administering of peritoneal dialysis treatments as well as patient teaching about both the nature and mechanics of the treatment.
- Registered dietitians will be very important in the patient's treatment planning and education, as diet is an essential part of treatment.
- Social workers will usually be involved in helping the patient to obtain the necessary financial assistance to deal with the tremendous financial burden kidney disease can impose. They may also counsel the patient or family in coping with this difficult illness.
- Clinical laboratory scientists have specialized training and must pass a state examination. They draw blood samples or test urine specimens to determine the level of various chemicals in the blood stream or urine.
Bowman's capsule—The expanded end of a kidney tubule or nephron that acts as a filter to produce urine.
Diabetes mellitus—A disorder in which the pancreas secretes little or no insulin, the hormone responsible for the metabolism of carbohydrates.
Glomerulonephritis—Inflammation of the glomeruli, the filtering units of the kidney.
Hilum—The recessed area at the entrance of the renal artery entering, and the renal vein exiting the kidney.
Inferior vena cava—One of two of the largest veins in the body that enter the right atrium of the heart.
Lupus erythematosus—A chronic disease characterized by inflammation of the connective tissue. The more serious form of this disease affects the kidneys.
Osmosis—The process of a liquid passing through a semi-permeable membrane from a less concentrated solution to a more concentrated one until both solutions have the same strength.
Uremic encephalopathy—The presence of too much urea, a waste product produced by the breakdown of proteins, and other toxins that cause abnormality within the brain. Uremia occurs as a result of kidney failure.
Ureter—One of the two long, slender tubes approximately 10–20 in (25.4–50.8 cm) in length that carry urine from the kidney to the bladder.
Berkow, Robert, et al., eds. Merck Manual of Diagnosis and Therapy, Home Edition. Merck Research Laboratories, 1997.
Kozier, Barbara, et al. Fundamentals of Nursing, Concepts, Process and Practice. Addison-Wesley Publishing Co, Inc., 1995.
National Institute of Health. 3 Information Way, Bethseda, MD 20892-3580.
Joan M. Schonbeck