What is dialysis?
Dialysis is for people who have kidney failure. When you have kidney failure, your kidneys are not able to cleanse your blood of wastes, including urea, and extra fluid. This process takes about three hours and is done three times a week.
What is hemodialysis?
Hemodialysis is a procedure that withdraws blood from the body into a machine that uses a special membrane (dialyzer) to filter wastes and remove extra fluid from the blood. Hemodialysis also restores the electrolyte balance in the blood.
Why do I need hemodialysis?
Hemodialysis is often started when symptoms or signs of kidney failure appear. These may include:
- Nausea, vomiting, anorexia, and fatigue due to "uremia", a buildup of urea and other waste products in the blood that occurs when the kidneys are unable to eliminate wastes from your body. These wastes are poisonous to you when they reach high levels.
- High levels of potassium in the blood ("hyperkalemia")
- Fluid overload
- High levels of acid in the blood
- Hemodialysis is sometimes used for people who have acute (sudden) kidney failure.
Are there any risks associated with hemodialysis?
Dialysis is always used with extra caution in people who have acute kidney failure. Dialysis can cause low blood pressure, an irregular heart rhythm (cardiac arrhythmia) and other problems that can sometimes make acute kidney failure worse.
What is a hemodialysis access?
Because of the need to remove blood from the body and replace it during hemodialysis, a means for accessing the patient's blood circulation -- called "vascular access" -- is necessary. There are three different techniques for this, some of which are used interchangeably: dialysis fistula, graft and catheter. All of these techniques are able to withdraw and replace large amounts of blood at the same time - about one quart per minute.
What is a fistula?
The most desirable form of hemodialysis vascular access is called a fistula. To make a fistula, a surgeon connects an artery to a vein in the forearm or upper arm. With time, usually one to three months, the vein enlarges and becomes ready to receive the needles used to withdraw and replace blood during dialysis. A fistula can last for many years if the vein enlarges and the fistula "develops". About three-quarters of fistulas develop or mature. During the time that a fistula is developing, if hemodialysis is necessary, another form of vascular access will be necessary, usually a catheter.
What if my fistula does not develop?
A non-developing or non-maturing fistula occurs in up to one fourth of patients. There are two causes for a non-maturing fistula: narrowing of a vein or too many competing veins. Interventional radiologists can either open up the narrowed vein with a balloon (balloon angioplasty) or close off the competing veins using several techniques. About three quarters of people with non-maturing fistulae will benefit from one or both of these treatments and have their fistula develop so it can be used. These procedures are done as an outpatient and take about an hour.
Protect your veins!
In order to make a fistula you must have good arteries and good veins. While you generally cannot do much about your arteries, you are in control of your veins. As soon as a diagnosis of kidney failure is made you should be very careful not to let anyone puncture the veins of your forearm or upper arm for blood draws, intravenous medications, or for any other reason. The hand veins should serve this purpose. By doing so, you protect your important veins so the surgeon will have a better chance of making a fistula. Even after a hemodialysis access is created in one arm, you should protect the veins of the opposite arm.
What is a dialysis graft?
In some patients, the arteries and/or veins are not suitable for making a fistula. In these patients, a shunt (or graft) can be used as an alternative form of dialysis access. A graft is a piece of plastic tubing that is inserted by a surgeon and connects the artery to the vein. Unlike fistulas, grafts do not need to "develop" and are ready for use in most instances by four weeks after placement. A catheter may be necessary for dialysis during this waiting period. The disadvantage of grafts is that they do not last nearly as long as fistulas and can develop narrowing and clotting more frequently. In addition, grafts can get infected -- something which does not happen very often with fistulas.
Just as with fistulas, narrowing veins with grafts can be detected before they clot if the appropriate screening techniques are used. These include self-examination, measuring flows during dialysis with a special machine, and checkups by an interventional radiologist. Once an abnormality is detected, you need to be scheduled to have it treated by Interventional Radiology as quickly as possible. It is very important that patients keep their appointments with Interventional Radiology so that clotting does not occur. If clotting does occur it can be treated by an interventional radiologist.
What is a dialysis catheter?
Catheters are considered the least desirable form of dialysis access. Catheters come in two forms: a short-term (non-tunneled) and longer-term (tunneled) form. The best use of catheters is to provide short-term access for dialysis for patients whose kidney function is expected to recover, or for patients whose kidney function is not expected to recover but who have a graft or fistula in place and are waiting for it to mature.
A catheter is inserted by an interventional radiologist or a nephrologist (kidney doctor) through one of the large veins -- usually the jugular -- into the larger veins in the center of the chest near the heart. This procedure can be done as an outpatient and lasts less than an hour. The best results with catheter placement are achieved when imaging guidance is used, including ultrasound to place a needle into the vein and X-rays to guide correct positioning of the catheter.
Catheters have the advantage that they can be used for dialysis immediately after they are placed. Patients also tend to find them attractive because needle sticks are not necessary to remove and replace blood during dialysis, as occurs with a graft or fistula. However, catheters have significant disadvantages and risks. These include:
- Risk of infection - approximately half of all patients with catheters develop a life-threatening infection during the first year the catheter is in place.
- Catheters do not provide flow rates for dialysis that are as good as grafts or fistulas. This can result in patients not receiving enough dialysis or requiring a longer dialysis session.
- Catheters can cause the veins they are placed into to clot off or develop narrowing (stenosis). In fact, with certain chest veins called the subclavian veins (just under the collarbone), the risk of clotting or narrowing is approximately 50%. Therefore, subclavian veins should never be used for catheters except in very rare instances when all other veins have been used up. Patients can help to prevent this complication by not allowing their doctors to use the subclavian veins for dialysis catheters, rather insisting on the jugular veins where this complication is quite uncommon (less than 10%)
- Many patients find catheters uncomfortable and/or unsightly.
Despite all of the problems with catheters, patients may need to have them in place for a short period of time while a fistula develops or a graft heals. Generally, this should be less than three months for a fistula and one month for a graft. Some patients will need to have a catheter placed while they are waiting for a visit to the surgeon for a graft or fistula. It is very important that patients in this situation make and keep their appointments with the surgeon so there is no delay in getting the graft or fistula made. The sooner the catheter comes out, the better.
Besides inserting dialysis catheters, interventional radiologists also treat problems with catheters, including infection and clotting. These problems are most commonly treated by exchanging the catheter for a new one in a brief outpatient procedure lasting less than an hour.
What if problems are detected with my graft or fistula?
While a fistula is considered the best kind of access, problems can occur, including vein narrowing, or "stenosis," and clotting, or "thrombosis". Both of these problems can be treated by an interventional radiologist with excellent results. Treating the vein while it is narrowed but not clotted yields the best results and takes the least amount of time. There are a number of ways to detect narrowing in the vein before thrombosis occurs, through "screening" with your Dialysis Unit. Once an abnormality is detected it is essential that you be seen by the interventional radiologist as soon as possible to treat the problem.
What if my dialysis access is clotted?
If the graft or fistula is clotted, interventional radiologists use a variety of procedures to dissolve or remove the clot. First, X-ray pictures (fistulograms) are taken which show the area(s) of narrowing (stenosis). Then, a balloon is inserted to open up the clogged area(s) in the vein, in a procedure called an "angioplasty". A clot can be removed either with drugs that dissolve it or mechanical devices that remove it or break it up into very small pieces.
These procedures are all done as an outpatient using conscious sedation and local anesthesia (numbing medicine). In conscious sedation, medicines to relieve anxiety and discomfort are given through an intravenous tube. In order to receive conscious sedation, you must not have had anything to eat or drink six hours before your procedure. Also, you may not drive home after receiving conscious sedation, so be sure to arrange a ride home after the procedure.
After angioplasty, your self-examination should return to normal. Screening tests should be repeated in the Dialysis Unit to ensure that they too have returned to normal. While balloon angioplasty is effective in dialysis access it may need to be repeated periodically, usually every six months. When angioplasty is unsuccessful, interventional radiologists have other alternatives available to them. Generally, the first of these is to repeat the angioplasty. If this is unsuccessful, depending upon the location of the narrowing, a small metal tube called a "stent" can be inserted in the same outpatient procedure as the angioplasty. This is done quite uncommonly and more often in the chest than the arms. When angioplasty is unsuccessful, a patient may be referred to a surgeon for a procedure called a "revision of the graft or fistula".
What is dialysis access self-examination?
Your dialysis graft or fistula should feel like a cat purring when it is functioning well. You can feel this best by putting the palm of your hand over your graft or fistula. You should examine at least three different points on the access. If you feel the access pulsing (beating like a drum), this is abnormal and you should inform the Dialysis Unit staff immediately so a fistulogram and angioplasty can be scheduled. The best way to detect problems with your graft or fistula is to examine it on a regular basis (such as on your dialysis days) and note changes from the last self-examination. If you cannot feel a pulse or a thrill, your access is probably clotted and you may wish to call the Dialysis Unit to inform them so you can get it treated.
Arm swelling is also abnormal and may be an indication of a problem in the veins of the chest. Some swelling after a surgical procedure may be normal but this should get progressively better. Swelling that lasts more than a few weeks after surgery should be investigated with a fistulogram.
Tenderness or redness over a graft is a sign of infection and should be reported to the Dialysis Unit staff immediately. In a clotted fistula, some tenderness or redness may be normal, but never in a clotted graft.
What are the screening tests for a failing dialysis access?
Screening for a failing dialysis access can be done in several ways. The simplest is self-examination. Other techniques available during dialysis include flow measurement (using a special machine connected to your dialysis tubing) and pressures (measured by the dialysis machine). When a graft or fistula is failing, the flow goes down and generally the pressure goes up. Other signs that an access is failing include prolonged bleeding after needle removal and trouble puncturing the access. Any of these abnormalities should prompt a visit to Interventional Radiology for a fistulogram and balloon angioplasty as needed.
Are there any other treatments for kidney failure?
Other than dialysis, kidney transplantation is the only other option for people with kidney failure. In kidney transplantation, a kidney received from an organ donor or a living relative is placed into the body and takes over the function of the failed kidneys. Kidney transplant is the desired goal for most people with kidney failure. However, due to a shortage of donor kidneys, the majority of people with kidney failure are on dialysis.