kidney dialysis

Also found in: Dictionary, Thesaurus, Encyclopedia.

Dialysis, Kidney



Dialysis treatment replaces the function of the kidneys, which normally serve as the body's natural filtration system. Through the use of a blood filter and a chemical solution known as dialysate, the treatment removes waste products and excess fluids from the bloodstream, while maintaining the proper chemical balance of the blood. There are two types of dialysis treatment: hemodialysis and peritoneal dialysis.


Dialysis can be used in the treatment of patients suffering from poisoning or overdose, in order to quickly remove drugs from the bloodstream. Its most prevalent application, however, is for patients with temporary or permanent kidney failure. For patients with end-stage renal disease (ESRD), whose kidneys are no longer capable of adequately removing fluids and wastes from their body or of maintaining the proper level of certain kidney-regulated chemicals in the bloodstream, dialysis is the only treatment option available outside of kidney transplantation. In 1996 in the United States, over 200,000 people underwent regular dialysis treatments to manage their ESRD.


Blood pressure changes associated with hemodialysis may pose a risk for patients with heart problems. Peritoneal dialysis may be the preferred treatment option in these cases.
Peritoneal dialysis is not recommended for patients with abdominal adhesions or other abdominal defects, such as a hernia, that might compromise the efficiency of the treatment. It is also not recommended for patients who suffer frequent bouts of diverticulitis, an inflammation of small pouches in the intestinal tract.


There are two types of dialysis treatment: hemodialysis and peritoneal dialysis:


Hemodialysis is the most frequently prescribed type of dialysis treatment in the United States. The treatment involves circulating the patient's blood outside of the body through an extracorporeal circuit (ECC), or dialysis circuit. Two needles are inserted into the patient's vein, or access site, and are attached to the ECC, which consists of plastic blood tubing, a filter known as a dialyzer (artificial kidney), and a dialysis machine that monitors and maintains blood flow and administers dialysate. Dialysate is a chemical bath that is used to draw waste products out of the blood.
Since the 1980s, the majority of hemodialysis treatments in the United States have been performed with hollow fiber dialyzers. A hollow fiber dialyzer is composed of thousands of tube-like hollow fiber strands encased in a clear plastic cylinder several inches in diameter. There are two compartments within the dialyzer (the blood compartment and the dialysate compartment). The membrane that separates these two compartments is semipermeable. This means that it allows the passage of certain sized molecules across it, but prevents the passage of other, larger molecules. As blood is pushed through the blood compartment in one direction, suction or vacuum pressure pulls the dialysate through the dialysate compartment in a countercurrent, or opposite direction. These opposing pressures work to drain excess fluids out of the bloodstream and into the dialysate, a process called ultrafiltration.
A second process called diffusion moves waste products in the blood across the membrane into the dialysate compartment, where they are carried out of the body. At the same time, electrolytes and other chemicals in the dialysate solution cross the membrane into the blood compartment. The purified, chemically balanced blood is then returned to the body.
Most hemodialysis patients require treatment three times a week, for an average of three-four hours per dialysis "run." Specific treatment schedules depend on the type of dialyzer used and the patient's current physical condition. While the treatment prescription and regimen is usually overseen by a nephrologist (a doctor that specializes in the kidney), dialysis treatments are typically administered by a nurse or patient care technician in outpatient clinics known as dialysis centers, or in hospital-based dialysis units. In-home hemodialysis treatment is also an option for some patients, although access to this type of treatment may be limited by financial and lifestyle factors. An investment in equipment is required and another person in the household should be available for support and assistance with treatments.

Peritoneal dialysis

In peritoneal dialysis, the patient's peritoneum, or lining of the abdomen, acts as a blood filter. A catheter is surgically inserted into the patient's abdomen. During treatment, the catheter is used to fill the abdominal cavity with dialysate. Waste products and excess fluids move from the patient's bloodstream into the dialysate solution. After a waiting period of six to 24 hours, depending on the treatment method used, the waste-filled dialysate is drained from the abdomen, and replaced with clean dialysate.
There are three types of peritoneal dialysis:
  • Continuous ambulatory peritoneal dialysis (CAPD). A continuous treatment that is self-administered and requires no machine. The patient inserts fresh dialysate solution into the abdominal cavity, waits four to six hours, and removes the used solution. The solution is immediately replaced with fresh dialysate. A bag attached to the catheter is worn under clothing.
  • Continuous cyclic peritoneal dialysis (CCPD). An overnight treatment that uses a machine to drain and refill the abdominal cavity, CCPD takes 10-12 hours per session.
  • Intermittent peritoneal dialysis (IPD). This hospital-based treatment is performed several times a week. A machine administers and drains the dialysate solution, and sessions can take up to 24 hours.
Peritoneal dialysis is often the treatment option of choice in infants and children, whose small size can make vascular (through a vein) access difficult to maintain. Peritoneal dialysis can also be done outside of a clinical setting, which is more conducive to regular school attendance.


Patients are weighed immediately before and after each hemodialysis treatment to assess their fluid retention. Blood pressure and temperature are taken and the patient is assessed for physical changes since their last dialysis run. Regular blood tests monitor chemical and waste levels in the blood. Prior to treatment, patients are typically administered a dose of heparin, an anticoagulant that prevents blood clotting, to ensure the free flow of blood through the dialyzer and an uninterrupted dialysis run for the patient.


Both hemodialysis and peritoneal dialysis patients need to be vigilant about keeping their access sites and catheters clean and infection-free during and between dialysis runs.
Dialysis is just one facet of a comprehensive treatment approach for ESRD. Although dialysis treatment is very effective in removing toxins and fluids from the body, there are several functions of the kidney it cannot mimic, such as regulating high blood pressure and red blood cell production. Patients with ESRD need to watch their diet and fluid intake carefully and take medications as prescribed to manage their disease.


Many of the risks and side effects associated with dialysis are a combined result of both the treatment and the poor physical condition of the ESRD patient. Dialysis patients should always report side effects to their healthcare provider.


Hematocrit (Hct) levels, a measure of red blood cells, are typically low in ESRD patients. This deficiency is caused by a lack of the hormone erythropoietin, which is normally produced by the kidneys. The problem is elevated in hemodialysis patients, who may incur blood loss during hemodialysis treatments. Epoetin alfa, or EPO (sold under the trade name Epogen), a hormone therapy, and intravenous or
Hemodialysis is the most frequently prescribed type of dialysis treatment in the United States. This treatment involves circulating the patient's blood outside of the body through a dialysis circuit. The blood is filtered and cleansed inside the hemodialyzer and returned to the body.
Hemodialysis is the most frequently prescribed type of dialysis treatment in the United States. This treatment involves circulating the patient's blood outside of the body through a dialysis circuit. The blood is filtered and cleansed inside the hemodialyzer and returned to the body.
(Illustration by Electronic Illustrators Group.)
oral iron supplements are used to manage anemia in dialysis patients.

Cramps, nausea, vomiting, and headaches

Some hemodialysis patients experience cramps and flu-like symptoms during treatment. These can be caused by a number of factors, including the type of dialysate used, composition of the dialyzer membrane, water quality in the dialysis unit, and the ultrafiltration rate of the treatment. Adjustment of the dialysis prescription often helps alleviate many symptoms.


Because of the stress placed on the cardiovascular system with regular hemodialysis treatments, patients are at risk for hypotension, a sudden drop in blood pressure. This can often be controlled by medication and adjustment of the patient's dialysis prescription.


Both hemodialysis and peritoneal dialysis patients are at risk for infection. Hemodialysis patients should keep their access sites clean and watch for signs of redness and warmth that could indicate infection. Peritoneal dialysis patients must follow the same precautions with their catheter. Peritonitis, an infection of the peritoneum, causes flu-like symptoms and can disrupt dialysis treatments if not caught early.

Infectious diseases

Because there is a great deal of blood exposure involved in dialysis treatment, a slight risk of contracting hepatitis B and hepatitis C exists. The hepatitis B vaccination is recommended for most hemodialysis patients. As of 1997, there had only been one documented case of HIV being transmitted in a United States dialysis unit to a staff member, and no documented cases of HIV ever being transmitted between dialysis patients in the United States. The strict standards of infection control practiced in modern hemodialysis units makes the chance of contracting one of these diseases very small.

Normal results

Puffiness in the patient related to edema, or fluid retention, may be relieved after dialysis treatment. The patient's overall sense of physical well-being may also be improved. Because dialysis is an ongoing treatment process for many patients, a baseline for normalcy can be difficult to gauge.



American Association of Kidney Patients. 100 S. Ashley Dr., #280, Tampa, FL 33602. (800) 749-2257.
American Kidney Fund (AKF). Suite 1010, 6110 Executive Boulevard, Rockville, MD 20852. (800) 638-8299.
National Kidney Foundation. 30 East 33rd St., New York, NY 10016. (800) 622-9010.
United States Renal Data System (USRDS). The University of Michigan, 315 W. Huron, Suite 240, Ann Arbor, MI 48103. (734) 998-6611. 〈〉.

Key terms

Access site — The vein tapped for vascular access in hemodialysis treatments. For patients with temporary treatment needs, access to the bloodstream is gained by inserting a catheter into the subclavian vein near the patient's collarbone. Patients in long-term dialysis require stronger, more durable access sites, called fistulas or grafts, that are surgically created.
Dialysate — A chemical bath used in dialysis to draw fluids and toxins out of the bloodstream and supply electrolytes and other chemicals to the bloodstream.
Dialysis prescription — The general parameters of dialysis treatment that vary according to each patient's individual needs. Treatment length, type of dialyzer and dialysate used, and rate of ultrafiltration are all part of the dialysis prescription.
Dialyzer — An artificial kidney usually composed of hollow fiber which is used in hemodialysis to eliminate waste products from the blood and remove excess fluids from the bloodstream.
Erythropoietin — A hormone produced by the kidneys that stimulates the production of red blood cells by bone marrow.
ESRD — End-stage renal disease; chronic or permanent kidney failure.
Extracorporeal circuit (ECC) — The path the hemodialysis patient's blood takes outside of the body. It typically consists of plastic tubing, a hemodialysis machine, and a dialyzer.
Hematocrit (Hct) level — A measure of red blood cells.
Peritoneum — The abdominal cavity; the peritoneum acts as a blood filter in peritoneal dialysis.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


 [di-al´ĭ-sis] (Gr.)
1. the diffusion of solute molecules through a semipermeable membrane, normally passing from the side of higher concentration to that of lower. A semipermeable membrane is one that allows the passage of certain smaller molecules of such crystalloids as glucose and urea, but prevents passage of larger molecules such as the colloidal plasma proteins and protoplasm. adj., adj dialyt´ic.
continuous ambulatory peritoneal dialysis (CAPD) peritoneal dialysis involving the continuous presence of dialysis solution in the peritoneal cavity; see discussion at peritoneal dialysis.
continuous cycling peritoneal dialysis (CCPD) a procedure similar to continuous ambulatory peritoneal dialysis but taking place at night, using a machine to make several fluid exchanges automatically. See discussion at peritoneal dialysis.
dialysis dysequilibrium syndrome a condition occasionally seen following overly rapid hemodialysis, characterized by increased intracranial pressure that causes nausea, headache, vomiting, restlessness, and a decreased level of consciousness. The neurological complications may lead to coma and death if not treated. The cause of this syndrome is thought to be the rapid decrease in the blood urea nitrogen that accompanies dialysis. Called also dialysis dysequilibrium.
extracorporeal dialysis dialysis by a hemodialyzer; see also hemodialysis.
intermittent peritoneal dialysis (IPD) an older form of peritoneal dialysis in which dialysis solution is infused into the peritoneal cavity, allowed to equilibrate for 10 to 20 minutes, and then drained out. See discussion at peritoneal dialysis.
kidney dialysis hemodialysis.
peritoneal dialysis see peritoneal dialysis.
renal dialysis hemodialysis.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

Patient discussion about kidney dialysis

Q. why the renal doctor told my husband that he needs to eat a dozen of egg a week for protein,how it will help? it won`t afect his cholesterol,also i would like to know what role the protein plays on his treatment and what other foot its rich in protein that he can can take,without causing problems to his health.

A. if i understand correctly, your husband is diabetic. like my grandfather he probably developed a "Diabetic nephropathy" which is a long name to: kidney being destroyed because of blood vessels clotted by diabetes. because of that destruction the kidneys allow protein to go out in the urine. this is a dangerous situation,a protein in the name of "albomin" helps our blood to hold fluids in blood vessels. without it fluid will leave the blood and go to our organs. not a good situation. so he needs a lot of proteins.
here is a list of a 100 protein rich foods:

More discussions about kidney dialysis
This content is provided by iMedix and is subject to iMedix Terms. The Questions and Answers are not endorsed or recommended and are made available by patients, not doctors.
References in periodicals archive ?
The show's first episode included a report on new advances in home-use kidney dialysis machines and the likelihood of discovering life on Mars.
The Indian Consul said Kidney Dialysis machine brought by the clinic will go a long way in solving illness relating to kidney.
"Fatema had to go for kidney dialysis every other day and I used to go with her," says Shayma.
Cardiovascular company Resverlogix Corp (TSX:RVX) stated on Monday that its Investigational New Drug (IND) application for the planned launch of a Phase 2a Apabetalone kidney dialysis trial in advanced chronic kidney disease (CKD) patients has been approved by the Cardiovascular and Renal Products Division of the US Food and Drug Administration (FDA).
Doctors are continuing to run tests and are hoping to reduce her kidney dialysis over the coming days.
This could immediately be assessed through the fast-raising figures of the kidney failure patients landing in the grand Kidney Dialysis Centre, operating in Mirpur Divisional Headquarter Hospital with the requisite financial assistance of a United Kingdom - based NGO - The Noor Foundation and its local sister NGO - Anjuman Falah e Bahbood -e-Insaniat Mirpur, for the required dialysis twice or thrice in a week.
The company is primarily engaged in providing kidney dialysis services and clinical laboratory testing; manufacturing and distributing products and equipment for kidney dialysis treatment; and providing other medical ancillary services.
For four years, she left school early three days a week to undergo kidney dialysis.
PATIENTS' lives could be put at risk by building a proposed health centre and kidney dialysis unit in the middle of an oil exploration zone, an expert has warned.
Beta blockers are commonly prescribed to patients undergoing kidney dialysis, to decrease the risk for sudden cardiac death.
PLANS to dump kidney dialysis patients on GPs has raised fears of a postcode lottery for treatment that could cost lives.
Though the 74-year-old remains in intensive care, kidney dialysis has