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:
- Your blood type is compatible with the recipient’s blood type, and how your tissue antigens match to the recipient’s antigens,
- You are healthy enough to withstand major surgery and recover completely, and
- 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 don’t have either antigen.
As a general rule, 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:
- Type A can donate to types A and AB.
- Type B can donate to types B and AB.
- Type AB can donate to type AB.
- 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. In a growing number of situations, more than two donor/recipient pairs are linked in an extended “chain” of donation. These chains have included as many as 34 donor/recipient pairs.
Here’s an example of a paired exchange. Assume in the first donor/recipient pair, the donor, Jim, is blood type A and the person he’d like to donate to, Lisa, is blood type B. Jim can’t donate to Lisa because they have incompatible blood types. In the second pair, the donor, Niki, is blood type B and she’d like to donate to Mike, but he’s blood type A. They are incompatible. Paired exchange provides the solution: Jim donates to Mike (both blood type A), and Niki donates to Lisa (both blood type B). Organizations have been formed to facilitate the matching of donor/recipient pairs. As a result, the number of paired exchanges has increased significantly.
The other option is called “plasmapheresis.” Plasmapheresis involves the transplant recipient undergoing a special medical process that removes the blood’s incompatible antigens. With removal of the recipient’s antigens, the donor is now able to donate. Note that plasmapheresis may be considered 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 this type of 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.
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 you—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 be tried 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 reducing the number of potential donors is because the remaining tests are more involved, time consuming, and expensive.
2. Your General Health
You will have a complete physical exam to ensure you are in good health and don’t have any health conditions that would rule you out as a donor. Standard procedures for a medical evaluation do not exist. However, LDO has assembled the following list of tests and medical procedures that are typically included in a donor evaluation.
- Physical exam including blood testing (cholesterol, blood count, creatinine, urea, etc.), blood pressure, height, weight, BMI calculation, personal medical history, family medical history, prescription drug use, substance abuse, smoking history, alcohol intake, history of mental illness and treatment, kidney history (stones, injury, etc.), chest x-ray, electrocardiogram, and testing for viral and bacterial infection (HIV, hepatitis, syphilis, herpes, tuberculosis, etc.).
- Fasting blood glucose test and, depending on diabetes risk factors, a glucose tolerance test.
- Echocardiogram and stress test if over age 50 or presence of other risk factors.
- Pulmonary function test and a chest CT scan for smokers.
- Female donor candidates undergo a gynecological exam, mammography (if over age 40), PAP, and pregnancy test.
- Male donor candidates may undergo a PSA test if over age 50.
- Potential donors over age 50 may undergo a colonoscopy.
Certain medical conditions will exclude you from being a donor. These conditions, called “contraindications,” vary from one transplant center to another because of the lack of common medical guidelines for evaluating living donors. However, to get an idea of the kinds of conditions that would typically exclude a donor, click here for a list of contraindications proposed by the UNOS Living Donor Committee.
If you are overweight but otherwise a good potential donor, you may be given time to lose weight. Several donors who visit LDO have indicated they were able to lose weight and donate successfully. If you are a smoker, it is suggested that you stop smoking at least four weeks prior to donation to reduce the risk of complications when recovering in the hospital (a smoke-free environment) from the surgery.
3. Health of Your Kidneys
In addition to a general assessment of your health, the donor evaluation focuses on the health and structure of your kidneys with these tests:
- Urine tests. You will be asked to undergo 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 and to calculate your glomerular filtration rate (GFR). Your urine will also be examined for the presence of blood and protein, and to ensure your urinary tract is not infected.
- Anatomical evaluation. You’ll undergo a procedure to identify the structure of the kidney, veins, arteries, the ureter, and other anatomy. One approach is a Computed Tomography (CT) Angiogram test, commonly called a CT scan, which is a sophisticated form of X-ray. For this procedure, 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 doughnut. The machine projects a thin x-ray beam through your body and measures the output. The dye gives more contrast to the blood vessels making them easier to identify. A computer takes the information from the x-ray scan and generates a three-dimensional image of your kidneys and surrounding anatomy. Another option is a Magnetic Resonance Angiogram (MRA). The MRA is a form of magnetic resonance imaging (MRI) designed to look at the structure of blood vessels. The MRA is similar to a CT scan except it uses radio waves and a magnet to measure magnetic fields in your body, which are used to construct images of your kidneys, arteries, and veins. You lie on a table that moves through a large magnet to make the measurements and create the images for review by the transplant team.
The information from the anatomical evaluation 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 result in consideration of the right kidney.
For tests that use x-rays, female donor candidates should inform the medical technician if you are pregnant or might be pregnant. Also, the tests use a dye that some people may have an allergic reaction to. Let the technician know if you have had allergic reactions in the past, especially to iodine.
4. Psychosocial Assessment
During the medical evaluation you will meet with a social worker, psychologist, or psychiatrist for a psychosocial assessment, the goal of which is to evaluate your state of mind. Generally, this assessment is done in a meeting during which the assessor asks you several questions about your level of understanding of the living donation process and risks, whether are you freely choosing to be a donor, and whether you are emotionally and psychologically ready for donation and recovery.
There are no standard procedures for this kind of assessment. However, the UNOS Living Donor Committee put together recommendations in 2007. The recommendations were not approved, but they are indicative of the kinds of subjects that may be covered in a typical psychosocial evaluation.
About Living Kidney Donation
- Why living kidney donation?
- The tap on the shoulder (being asked to donate)
- Now…about your health (donor evaluation)
- The gift (the surgical process)
Information Source: http://livingdonorsonline.org