Living donor evaluation

1. A surgery unlike any other

Living donor kidney transplantation has an exceptional feature: we operate on a healthy person who receives no direct medical benefit from the surgery. The donor accepts a nephrectomy to improve another person's health.

2. What must we demonstrate before accepting a donor?

Before the nephrectomy, we should be able to answer five questions:

1. Is the decision to donate truly free and voluntary?
2. Is the donor healthy enough to undergo major surgery?
3. Can the donor reasonably be expected to live safely with a single kidney?
4. Is the kidney we are going to remove suitable for the recipient?
5. Does the anatomy allow the nephrectomy and the transplant to be performed with acceptable risk?

These principles include medical and psychosocial evaluation, adequate kidney function, absence of transmissible diseases, and technical and immunological feasibility.

3. The evaluation must be done in stages

It makes no sense to begin by ordering the most complex and invasive tests. The workup should progress step by step:

1. Initial evaluation.
2. Rule out obvious contraindications.
3. Confirm adequate kidney function.
4. Psychosocial evaluation.
5. Donor-recipient compatibility.
6. Anatomical and vascular study.
7. Anesthetic evaluation.
8. Final multidisciplinary review.

This logical sequence avoids unnecessary procedures, especially invasive ones.

4. First question: do they really want to donate?

Donation must be free, conscious, voluntary, informed, and without coercion. The potential donor must understand what the surgery involves and be able to withdraw from the process.

The psychosocial evaluation seeks to detect:

• Family pressure.
• Coercion.
• Unrealistic expectations.
• Cognitive impairment.
• Relevant emotional problems.
• Financial motivations.
• Difficulty understanding the procedure.
• Absence of a truly autonomous decision.

The donor must not be subject to external pressure or seek material rewards.

5. Informed consent

Consent should not be simply the signing of a form before surgery. It is a process that begins during the evaluation. The donor must know about:

• General risks of surgery.
• Specific risks of nephrectomy.
• The possibility of complications.
• Consequences of living with a single kidney.
• The need for follow-up visits.
• Potential long-term impact.
• The possibility that the recipient may have complications.
• The possibility that the graft may fail.

The donor must even be informed of the possibility of loss of the recipient's graft and the need for prolonged medical follow-up of the donor.

6. Medical history

The medical evaluation must be complete. We must investigate:

• Kidney history.
• Hypertension.
• Diabetes.
• Obesity.
• Cardiovascular disease.
• Systemic diseases.
• Infections.
• Stone disease.
• Hematuria.
• Proteinuria.
• Neoplasms.
• Hereditary diseases.
• Family history of kidney disease.
• Previous surgeries.
• Smoking.
• Medications.
• Pregnancy and obstetric history when applicable.

It is especially important to know the cause of the recipient's CKD, particularly when hereditary kidney disease is a possibility.

7. Evaluation of kidney function

This is one of the pillars of selection. It is not enough to ask "is the creatinine normal?" We want to estimate: what is the current kidney function, and what renal reserve will this person have after donating?

The initial evaluation includes creatinine and estimation of the glomerular filtration rate, with more precise measurement when needed. In selected situations, isotopic studies and differential assessment of the two kidneys are considered.

The decision must take into account:

• Age.
• Sex.
• GFR.
• Albuminuria/proteinuria.
• Blood pressure.
• Diabetes and metabolic risk.
• Family history.
• Systemic diseases.
• Future kidney risk.

8. The two kidneys do not always function equally

When there is renal asymmetry or a relevant difference between the two kidneys, it may be necessary to study differential function. This introduces a fundamental principle: whenever possible, we should leave the donor the better kidney.

The recommendation is to select the kidney with lower function for nephrectomy when there is a relevant functional difference. But function is not the only element: we must also consider vascular and urinary anatomy.

9. Proteinuria and albuminuria

Protein in the urine can be a marker of underlying kidney disease. That is why the potential donor must be evaluated for albuminuria, proteinuria, and sediment abnormalities. A persistent abnormality requires investigation of its cause before donation is accepted.

The principle is clear: the donor should have normal kidneys and adequate function, with no proteinuria or sediment abnormalities suggestive of nephropathy.

10. Microscopic hematuria

Hematuria should not be ignored simply because the donor is asymptomatic. Persistent hematuria may be related to stone disease, infection, urological pathology, glomerular disease, or neoplasia, so it must be investigated before donation is accepted. Persistent microscopic hematuria warrants additional evaluation.

11. Blood pressure

Blood pressure deserves careful evaluation. We should not necessarily rely on a single office measurement. When values are borderline, hypertension is suspected, measurements are discordant, or other risk factors are present, it may be useful to perform ambulatory blood pressure monitoring (ABPM), which is more informative than a single office reading.

Hypertension should be analyzed together with: age + kidney function + albuminuria + target organ damage + overall cardiovascular risk.

12. Obesity and metabolic risk

BMI alone also does not tell the whole story. We should look for hypertension, impaired glycemia, albuminuria, dyslipidemia, sleep apnea, cardiovascular disease, fatty/metabolic liver disease, and family history. Obesity should be analyzed together with associated metabolic comorbidities, and a healthy lifestyle should be part of the donor's counseling.

13. Infections and transmissible diseases

The donor must be evaluated to avoid transmitting an infection to the immunosuppressed recipient. The evaluation should consider relevant infections according to epidemiology, history, place of origin, exposure, and program protocols. In addition, an active infection can increase the donor's own surgical risk.

The urine must be free of infection at the time of donation, and bacteriuria must be treated beforehand.

14. Oncological evaluation

We must also minimize the risk of transmitting a malignancy. The workup includes personal history, family history, physical examination, screening appropriate for age, sex, and risk, and targeted testing whenever there is any suspicion. The second-phase evaluation specifically includes cancer screening and additional individualized studies.

15. Cardiovascular and anesthetic evaluation

Even if the donor is healthy, they will undergo major surgery under general anesthesia. Cardiovascular risk, functional capacity, history, physical examination, ECG, and additional studies according to risk, as well as respiratory risk, thrombotic risk, and anesthetic history, must be evaluated.

Not all donors require an extensive battery of cardiology studies. The evaluation should be individualized according to risk.

16. Donor-recipient compatibility

The evaluation does not end with the kidney. We must also establish the immunological relationship between donor and recipient. Conceptually, we need to know: ABO group, HLA, anti-HLA antibodies, recipient sensitization, and crossmatch. The goal is to understand the immunological risk and establish whether the transplant can proceed directly or requires a specific strategy.

17. CT angiography: the surgeon's map

Once we know the donor can be a candidate, we need to know the anatomy precisely. Imaging should allow us to assess:

• Size.
• Symmetry.
• Lesions.
• Scars.
• Masses.

• Number.
• Origin.
• Accessory arteries.
• Early bifurcations.
• Caliber.
• Anomalies.

• Number.
• Length.
• Variants.
• Tributaries.
• Anatomy relevant to the nephrectomy.

• Collecting system.
• Duplications.
• Dilations.
• Anomalies.

CT angiography allows detailed characterization of the parenchyma, vasculature, and urinary tract.

18. Which kidney should we remove?

This is a central surgical decision. The conceptual rule should be: first we protect the donor, then we facilitate the transplant. That is why we must integrate:

• Differential kidney function.
• Vascular anatomy.
• Urinary anatomy.
• Complexity of the nephrectomy.
• Feasibility of implantation.

When there is a relevant functional difference, the goal is generally to preserve the kidney with better function for the donor.

19. Why has the left kidney historically often been preferred?

When both kidneys are functionally and anatomically equivalent, the left kidney usually offers a surgical advantage: a longer renal vein, which can facilitate back-table surgery and the venous anastomosis in the recipient.

But "left" does not automatically mean "the kidney to remove." The decision must be individualized.

20. Do multiple arteries contraindicate donation?

Not necessarily. The presence of multiple arteries, certain venous variants, or a duplicated collecting system may increase technical complexity, but is not in itself an absolute contraindication. The decision must integrate the team's experience, the possibility of reconstruction, and the safety of both donor and recipient.

21. When should we stop the evaluation?

If a condition that makes donation unacceptable appears during the early stages, there is no point in continuing to subject the patient to unnecessary tests. This sequential approach — initial screening, assessing whether a relevant contraindication exists, and, as appropriate, stopping/studying specifically/reevaluating or continuing the evaluation — is expressly recommended as the way to proceed.

22. The final decision is not an individual one

Acceptance of the donor should not depend exclusively on the surgeon who will perform the nephrectomy. Those involved are: Nephrology, Urology/Transplant surgery, Anesthesiology, Psychology/Psychiatry, Immunology, Infectious diseases when applicable, Cardiology or other specialties when necessary, and the transplant team.

The final decision must balance: donor safety + organ quality + recipient risk + technical feasibility.

Person who wishes to donate:

• No → do not continue.
• Yes → continue the evaluation.

• Yes → stop / treat / reevaluate depending on the situation.
• No → continue.

GFR + albuminuria/proteinuria + sediment ± differential function.

Hypertension + diabetes/metabolism + obesity + family history + cardiovascular risk.

ABO + HLA + antibodies + crossmatch.

Arteries + veins + parenchyma + urinary tract.

Which one leaves the donor in the best condition? Can that kidney be safely transplanted?

Before accepting a living donor, you should be able to answer:

• ☐ Do they freely want to donate?
• ☐ Do they understand the risks?
• ☐ Can they withdraw from the process?
• ☐ Do they have adequate kidney function?
• ☐ Do they have albuminuria/proteinuria?
• ☐ Do they have hematuria?
• ☐ Do they have hypertension or metabolic risk?
• ☐ Is there a risk of hereditary kidney disease?
• ☐ Is there a transmissible infection?
• ☐ Is there a relevant oncological risk?
• ☐ Are they immunologically compatible?
• ☐ What do the renal arteries look like?
• ☐ What do the veins look like?
• ☐ What does the urinary tract look like?
• ☐ Is there a functional difference between the two kidneys?
• ☐ Which kidney should we leave the donor?
• ☐ Which kidney are we going to remove?