A patient diagnosed with end-stage renal disease by a nephrology specialist should be referred without delay to the nearest organ transplant center. At the transplant center, the nephrologist first evaluates the patient for the possibility of a living donor kidney transplant. If living donor transplantation is not an option, the patient is initiated on an appropriate dialysis modality and subsequently placed on the deceased donor waiting list.
For patients who have not yet started dialysis or who are already undergoing dialysis treatment, close relatives who are blood group compatible and do not have hypertension, diabetes, or kidney disease are identified. The nephrologist refers both the patient and potential donor candidates to the transplant coordinator. At the center, blood group testing is repeated, and after lymphocyte crossmatch (LCM) testing, a psychiatric consultation is requested to assess the suitability of both the patient and the potential donor for transplantation.
Patients and donors with no issues in these evaluations are examined by the nephrology and surgical teams. In our center, tissue compatibility is not considered an absolute requirement for living donor transplantation.
All test results and clinical evaluations are reviewed by a medical board, which makes the final decision regarding the transplant eligibility.
BENEFITS OF KIDNEY TRANSPLANTATION
Undoubtedly, kidney transplantation is the best treatment option for patients with end-stage renal disease. Dialysis methods (hemodialysis or peritoneal dialysis), even under the best conditions, can only perform about 5% of the work done by two healthy kidneys. A successfully transplanted kidney, on the other hand, can perform up to ten times that amount—approximately 50% of the function of two healthy kidneys.
Most transplant patients feel much more energetic and better than they did while on dialysis. Many are able to return to jobs they couldn’t do before, and their chances of finding employment are higher compared to dialysis patients. In most cases, there is a significant improvement in sexual health compared to the dialysis period. Female patients are more likely to conceive and can give birth to healthy children.
WHAT IS PRE-EMPTIVE KIDNEY TRANSPLANTATION? (TRANSPLANT BEFORE STARTING DIALYSIS)
Pre-emptive kidney transplantation refers to a transplant performed on patients whose kidney filtration (glomerular filtration rate) has fallen below 20 ml/min but who have not yet started any form of dialysis treatment.
Among all transplantation approaches, this method yields the most successful outcomes. For this reason, it is very important that patients diagnosed with chronic kidney disease—especially those who are rapidly progressing toward end-stage renal failure (such as diabetic patients)—are referred to transplant centers before they reach end-stage kidney failure. This allows for early planning and decision-making regarding the appropriate treatment method (dialysis or transplantation).
In our center, pre-emptive kidney transplantation is only performed for candidates with a living donor; deceased donor transplantation is not available for these patients.
For patients with a living donor, every effort should be made to perform the transplant as soon as possible, ideally before the initiation of dialysis.
BLOOD TYPE COMPATIBILITY:
There are four main blood groups: A, B, AB, and O.
| RECIPIENT | DONOR |
|---|---|
| Type O | Can receive only from Type O |
| Type A | Can receive from Type A or O |
| Type B | Can receive from Type B or O |
| Type AB | Can receive from any group (O, A, B, or AB) |
Is transplantation impossible without blood type compatibility?
The importance of blood type in transplantation stems from the fact that these antigens are found not only on red blood cells but also on the surface of nearly all body cells. Blood group antigens act like identity cards for cells. Thanks to them, the immune system can distinguish between what belongs to the body and what is foreign. The main goal here is to make the recipient’s immune system recognize the donor’s blood group antigens as if they were its own.
To achieve this, special filters (similar to dialysis filters) are used to remove the antibodies in the recipient’s body that would otherwise identify the donor kidney as an “enemy.” Just like toxic substances are removed during dialysis, this procedure is repeated several times until transplantation becomes possible.
Our team has successfully performed blood type-incompatible kidney transplants in 8 patients.
The Rh factor (whether negative or positive) is not important for kidney transplantation. For example, a person with A(-) blood can donate a kidney to both A(-) and A(+) recipients. Similarly, for a deceased donor with B(+) blood, both B(-) and B(+) patients may be called for transplantation.
TISSUE COMPATIBILITY
Tissue typing is a blood test that reveals a person’s genetic makeup (genetic fingerprint). As with blood group compatibility, tissue compatibility between the donor and recipient is also evaluated.
While the success of deceased donor transplants largely depends on tissue compatibility, it has become clear that in living donor transplants, it is not as critical as once believed.
When comparing transplants between identical twins (with perfectly matched tissues) and those with no tissue match but compatible blood types, the 5-year graft survival rate in tissue-incompatible transplants is only about 7% lower—an almost negligible difference. Similarly, transplants with no tissue match and those with a 5 out of 6 tissue match show similar 5-year graft survival rates (approximately 80%).
Considering that nearly half of hemodialysis patients in our country do not survive past the fifth year, all patients should be given the opportunity for transplantation regardless of tissue compatibility, in order to increase their chances of survival.
A tissue type consists of a specific set of antigens inherited from a person’s parents, found on the surface of nearly all body cells. Like blood type, tissue type remains unchanged throughout life and serves as a unique biological code for each individual. Everyone has a tissue type made up of six different antigens.
There are three primary tissue antigens: A, B, and DR. Each individual inherits one set from their mother and one from their father, resulting in a total of 2A, 2B, and 2DR antigens.
Especially in deceased donor transplants, the more matching antigens there are between donor and recipient, the higher the likelihood that the kidney will function well. Among these antigens, DR matching is considered more important than A or B matching.
What Percentage of Tissue Compatibility Is Required for a Successful Transplant?
Tissue compatibility has lost its importance in living donor kidney transplants. However, in deceased donor transplants, recipients are selected by the Ministry of Health based on tissue compatibility.
It has been shown that transplants with 6 out of 6 (fully matched) tissue compatibility are more successful than those with 3 out of 6 or 4 out of 6 matches—especially in deceased donor cases. However, this does not mean that blood group and fully tissue-matched kidneys are guaranteed to succeed. The fact that even kidney transplants between identical twins (who have identical tissue types) can eventually be rejected suggests that there are other significant indicators on cell surfaces—beyond blood group and tissue type—that can lead to organ rejection.
Which Is More Important for Transplant Success: Blood Group Compatibility or Tissue Type Compatibility?
Blood group compatibility is much more critical than tissue type compatibility in determining transplant success.
Lymphocyte Crossmatch (LCM or Crossmatch Test):
In this test, the donor’s and recipient’s blood samples are mixed. It checks for the presence of antibodies in the recipient’s blood that could react with the donor kidney. Under normal circumstances, these antibodies help protect the body from infections.
If high levels of such antibodies are present, the recipient’s blood will react with the donor’s blood, and the test will come back positive. If a transplant is performed under these conditions, the kidney is likely to be lost within hours or days.
This is the first essential test that must be conducted after confirming blood and tissue compatibility for both living and deceased donor transplants. The likelihood of a positive crossmatch is higher in patients who have previously undergone kidney transplants or received blood transfusions. Therefore, blood transfusions should be avoided in dialysis patients unless absolutely necessary.
Does a Positive Crossmatch (LCM) Definitely Mean That a Transplant Cannot Be Performed?
A positive crossmatch does not mean that everything is over and that the patient can never undergo a transplant.
With the help of certain medications, it is possible to convert positive LCM results to negative, making transplantation feasible. At our center, we have successfully achieved an 85% conversion rate by gradually increasing the use of a medication containing the active substance “simvastatin.” This approach has led to two important outcomes:
- Many patients who were previously deemed ineligible for transplantation became suitable candidates.
- Not all positive LCM results are a barrier to transplantation.
The structure of the antibodies causing the LCM positivity is critical. If the antibodies are of the IgG type, it generally means the transplant is not possible at that time. However, if they are of the IgM type, transplantation can usually proceed safely. In other words, LCM positivity due to IgM antibodies is not a contraindication to kidney transplantation.