From the Director's Chair: How do You Know if You're Dialyzing Too Little or Too Much?

By Paul S. Kellerman, MD

How do your WDI caregivers know if you're getting enough dialysis for optimal health? That is a very good question. Dialysis gets rid of the waste products from your cells that go back into your blood, and also gets rid of salt and water you take in by mouth that your kidneys can no longer excrete.

First of all, we clinically assess you, both by asking you questions and sometimes examining you. Regarding the waste products, if you're not dialyzing enough, you may have symptoms of "uremia", which can include itching, nausea, poor appetite, restless legs or pain in your legs (neuropathy). Regarding the salt and water, we look at your fluid gains between dialysis, whether your blood pressure is high, whether you're having problems breathing, particularly when lying down, and whether you have swelling in your legs. Prior to 1990, a well-dialyzed patient was considered a patient who had none of these problems.

In the 1980's, dialysis times were shortened due to more efficient dialyzers and both patient and doctor preferences, and more patients started becoming ill. It was realized at that point that a certain amount of dialysis is best for feeling good on dialysis and long life on dialysis. It was also realized that we didn't really know how to measure how much dialysis a person needs for quality and quantity of life. The question of how much dialysis is enough has been an active area of research over the last 15 years. Is there something we can measure, aside from how you feel, to tell us how much dialysis is best? The answer is that we now have fairly good measures of how much dialysis is best for your health.

Monthly, you receive your report card, which describes your lab tests. On that report card is a "URR", which stands for urea reduction ratio. This is one measure of whether you are receiving enough dialysis. Another measure is a formula called the Kt/V. Let's talk about the URR, which you see monthly. Blood tests are drawn at the beginning and end of dialysis, measuring your BUN (blood urea nitrogen), and we calculate what percentage of BUN is removed. Through very large studies, it has been determined that the minimum acceptable reduction is 65%, but we feel that between 70-75% is optimal. How much dialysis you need also depends on your size. If you are a small person, you will need less dialysis than a large person.

The primary way we have to change your URR is the amount of time on dialysis, although we sometimes will first change to a larger artificial kidney to see if that helps.

Know your URR number each month, and if it is under 65%, you and your doctor should be talking about improving your dialysis adequacy, usually by increasing your time. No one likes being on dialysis for longer periods of time, but we only advise this in the interest of you living long and well on dialysis. Conversely, if your number is near 80%, then you may be able to decrease your time on dialysis.

Other conditions can decrease your URR. If you have a narrowing in your fistula or graft, that can cause recirculation (redialyzing the same blood, which is very inefficient). Sometimes, if we see a URR decrease, it makes us look for a narrowing in your fistula. It is also important on lab days that you complete your whole time on dialysis, to get an accurate URR. If you shorten your time that day, it will look like you don't routinely get enough dialysis.

So look at your URR and tell us if you don't feel well, so we can work in partnership with you to keep you in the best health possible.