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Now...About Your Health
Once you've agreed to be considered a donor, you'll go through an in-depth assessment of your health. It's your health that is of utmost importance to the transplant team. What they want to know is that:
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Your blood type is compatible with the recipient's blood type, and your tissue antigens are sufficiently close to the recipient's antigens.
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You are healthy enough to withstand major surgery and recover completely.
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You have a healthy kidney—preferably the left one—to donate, and you have a healthy kidney to keep—one that can compensate for the loss of a kidney.
With these three primary goals in mind, here is how donor candidates are medically evaluated.
1. Blood and Tissue Compatibility
Blood Type. The first step is to determine your blood type. There are four blood types, designated by the presence or absence of two antigens—the A antigen and the B antigen. Blood type A means you have the A antigen. Type B means you have the B antigen. Type AB means you have both antigens. Type O means you have neither antigen.
You must have a blood type compatible with the recipient or you will not be able to donate. Here is who can donate to whom:
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Type A can donate to types A and AB.
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Type B can donate to types B and AB.
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Type AB can donate to type AB.
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Type O can donate to types A, B, AB, and O.
The blood type is determined by drawing your blood and testing it.
If you and your potential recipient are not of the same blood
type, there are two things you can consider. One option is called
"paired exchange." Paired exchange involves finding another
donor-recipient pair who have incompatible blood types but your blood
type is compatible with the other recipient, and the other donor's
blood type is compatible with your potential recipient's blood type. In
that situation, you donate to the other recipient, and the other donor
donates to your recipient. This web
page illustrates how paired exchange works.
The other option is called "plasmapheresis." Plasmapheresis involves the transplant recipient undergoing removal of the spleen and a special medical process that removes the blood's incompatible antigens. With removal of the recipient's antigens, the donor is able to donate. This web page contains additional information. Note that plasmapheresis is still an experimental procedure and medical insurance may not cover the expense. Be sure to check the insurance plan before proceeding.
Tissue Type. A second test of compatibility looks at the match of human leukocyte antigens (HLA). There are many different kinds of antigens, but there are three categories assessed for kidney donation, designated HLA-A, HLA-B, and HLA-DR. You inherit one set of these three antigens from each parent giving you a total of six HLAs.
Your antigens are determined by drawing blood and testing it. A similar test is run for the recipient, and the antigens are compared. The closer the match the better because the recipient is less likely to reject the donated organ. You might hear of a "six-of-six" match (all donor and recipient antigens match) or a "half match" (three of the six antigens are the same) or a "zero match" (none of the antigens matches).
There was a time when tissue compatibility was important.
However, the development of more effective anti-rejection drugs has
reduced the importance of the HLA match. In fact, some transplant teams
ignore tissue typing. Therefore, even if your degree of matching with
the
donor is relatively low, you may still be considered for donation. See
this page for further discussion of HLA matching.
Crossmatching. The third blood test is an important one. Crossmatching is a further testing of antigen compatibility. In this test, white blood cells from you are mixed with blood from the recipient. If the white blood cells are attacked and die, then the crossmatch is "positive," which is a negative as far as your ability to donate. It means the recipient is "sensitized" to the donor—the recipient has antibodies to some of your antigens—so the recipient's immune system would turn on the donated organ and destroy it. If the crossmatch is "negative," you are compatible with the recipient.
For a donor and recipient with a "positive" crossmatch, plasmapheresis can also be used as a technique to allow the donation to proceed.
At this point, if there is more than one potential donor, the group is winnowed down to one or two. The reason for culling down the group at this point is because the remaining tests are more involved, time consuming, and expensive.
2. Your General Health
At some point in the screening process, you will have a complete physical exam. You will share your medical history and have a series of tests, such as a chest x-ray, electrocardiogram, blood tests, urine tests, and so on. Female donor candidates may also undergo a gynecological exam and mammography. The purpose of the exam is to ensure you don't have any health conditions that would rule you out as a donor.
3. Health of Your Kidneys
Following a general assessment of your health, the donor evaluation focuses on the integrity of your kidneys with these tests:
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Urine tests. You will be asked to undergo two 24-hour urine tests, called creatinine clearance tests. Creatinine is a chemical excreted in the urine and is a measure of kidney function. These tests are run to make sure your kidneys are functioning properly.
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Intravenous pyelography test. This test involves an injection of dye into a vein in your arm. The dye circulates through your body, into your kidneys, and then into your urinary tract. X-rays are taken to identify the structure of the kidney, veins, arteries, the ureter, and other anatomy.
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Renal arteriogram. This test is designed to identify the blood vessels of the kidney. The procedure is done in a hospital and is more invasive and time consuming than the other tests. For this test, you will change into a hospital gown and lie on a gurney. A small tube is inserted into your femoral artery in your leg and a dye is injected. (Some people feel pain or heat temporarily after the dye is released.) X-rays are taken to determine the mapping of your kidney's blood vessels. After this test, you are required to remain immobile for several hours. Because the test was done via an artery, the physician wants to be absolutely sure the wound is completely healed before you leave the hospital.
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Computed Tomography (CT) Angiography. The test, commonly called a CT scan, is a sophisticated form of X-ray and may be used in place of the renal arteriogram. In the case of a CT scan, a dye is injected into a vein, you lay flat on a table, and the table moves through a special machine shaped like a giant dough nut. The machine projects a thin x-ray beam through your body and measures the output. The dye helps gives more contrast to the blood vessels making them easier to identify. A computer takes the information from the x-ray scan and, using sophisticated mathematics, generates a three-dimensional image of your kidneys and surrounding anatomy. The CT scan gives more detailed information than an x-ray, is less invasive than the renal arteriogram, and can be less expensive. A research study showed CT scan results are equivalent to arteriography with lower cost and greater patient comfort (Florman, et al., 1998).
The information from this battery of tests is critical to the surgeon for determining which, if any, of your kidneys is best for donation. Generally, the left is preferred because of its longer renal artery. But there may be structural complications in the left kidney that would result in consideration of the right kidney.
Because these tests use x-rays, female donor candidates should inform the medical technician if you are pregnant. Also, the tests use a dye that some people may have an allergic reaction to. Again, let the technician know if you have had allergic reactions in the past, especially to iodine.
4. Other Assessments
Depending on hospital guidelines and transplant team protocol, there may be other assessments, such as psychological and financial reviews:
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A social worker or psychiatrist may evaluate your state of mind. What are your motives? What is your relationship to the recipient? Are you committed to donation or were you pressured? Do you have a support system, like friends and family, to help you after you donate?
This interview is an opportunity to explore any concerns you have about donation. Often, the transplant team will arrange to give you an "out" without embarrassment if you decide donation isn't for you.
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You may also be asked about financial considerations. Can you get off work for testing, surgery, and recovery? Medical expenses are covered by the medical insurance of the recipient, but lost wages are not. What kind of paid sick leave and vacation do you have from your employer? Do you have other financial resources available if you need them? Do you need help raising money?
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A potential donor must be an appropriate age. Policies vary by transplant center and exceptions are possible. Generally, at a minimum, the donor must legally be an adult (at least 18 years old) and legally competent. At a maximum, potential donors usually must not be older than 60. The reason is because the expected "life" of a donated kidney at an older age is limited.
