Residency · Residency · Urology
Evaluation of the Living Kidney Donor
Introduction
Living donor kidney transplantation offers the best outcomes for recipients with end-stage renal disease (ESRD), providing superior graft survival, shorter wait times, and the opportunity for preemptive transplantation before dialysis is required. However, evaluating a living donor requires adherence to the highest ethical and medical standards because the donor is a healthy individual undergoing a major surgical procedure solely for the benefit of another person. The evaluation process must carefully balance the benefits to the recipient against the risks to the donor, ensuring that the donor provides informed consent, is medically suitable, and is psychosocially prepared for donation.
Ethical Principles
The guiding ethical principle in living kidney donation is "primum non nocere," meaning that the donor must not be harmed; donor safety is the paramount concern throughout the process. Informed consent is essential, requiring that the donor fully understands the risks, benefits, alternatives, and their right to withdraw consent at any time without needing to provide an explanation. The Organ Procurement and Transplantation Network (OPTN) and United Network for Organ Sharing (UNOS) mandate the presence of an independent donor advocate (IDA) for every living donor. This advocate is separate from the recipient’s transplant team and serves to protect the donor’s interests. Voluntariness must be ensured, confirming that the donor is acting without coercion or undue pressure. Financial incentives for organ donation are illegal in the United States under the National Organ Transplant Act of 1984. Confidentiality is also critical; if a donor is deemed unsuitable, the specific reason need not be disclosed to the recipient. Instead, the transplant team simply states that the donor is "not a suitable candidate."
Medical Evaluation
General Health Assessment
The medical evaluation begins with a comprehensive history and physical examination. Donors are generally between 18 and 70 years old, although there is no strict upper age limit; advancing age is associated with increased perioperative risk. A body mass index (BMI) under 35 kg/m² is preferred. Donors with a BMI between 30 and 35 require additional metabolic evaluation, while a BMI over 35 is considered a relative contraindication due to increased surgical risk and a higher long-term risk of ESRD. Cardiovascular evaluation includes an electrocardiogram (ECG) and chest X-ray, with stress testing and echocardiography recommended for donors over 50 years or those with cardiac risk factors. Age-appropriate cancer screening must be up to date, and donors with prior malignancies must meet cancer-free interval requirements.
Renal Function Assessment
Assessment of renal function is critical. Serum creatinine and estimated glomerular filtration rate (eGFR) are measured, with most centers requiring an eGFR greater than 80 mL/min/1.73 m², and some requiring over 90. Measured GFR using nuclear renography (such as iothalamate or DTPA clearance) or 24-hour creatinine clearance is preferred for accuracy. A 24-hour urine collection assesses protein excretion, which should be less than 300 mg/day (some centers use a stricter cutoff of 150 mg/day), and confirms creatinine clearance. Urinalysis and urine culture exclude infection, hematuria, and proteinuria. Microalbuminuria is evaluated via the albumin-to-creatinine ratio, which should be below 30 mg/g; elevated levels warrant further investigation. Split renal function is assessed using MAG3 or DMSA scans to ensure both kidneys contribute adequately to overall renal function. Typically, the kidney with lesser function is selected for donation.
Metabolic and Hematologic Evaluation
Fasting glucose and HbA1c levels are measured because diabetes is an absolute contraindication to donation. Prediabetes, defined as an HbA1c between 5.7% and 6.4%, is a relative contraindication, especially if the donor has additional risk factors for progression to diabetes. A lipid panel is obtained to identify dyslipidemia, which is managed medically and is not a contraindication unless it is part of metabolic syndrome. A complete blood count is performed to exclude hematologic abnormalities, and hemoglobin electrophoresis is recommended for donors of African or Mediterranean descent; sickle cell trait is generally acceptable. Coagulation studies and hypercoagulability screening are done if there is a history suggesting thrombophilia. Liver function tests are also performed to exclude hepatic disease.
Infectious Disease Screening
Screening for infectious diseases includes testing for HIV 1/2 antibodies and nucleic acid testing (NAT); a positive result is an absolute contraindication except in cases of HIV-positive donors donating to HIV-positive recipients under the HOPE Act. Hepatitis B screening includes HBsAg, HBcAb, and HBsAb; active infection is a contraindication, but past infection with immunity may be acceptable. Hepatitis C antibody and NAT testing are performed; positive donors may donate to HCV-positive recipients under specific protocols. Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) serologies are important for recipient risk stratification, with CMV donor-positive/recipient-negative status posing the highest risk for CMV disease. Syphilis and tuberculosis screening are conducted according to OPTN guidelines. Urine culture is performed to detect active urinary tract infections, which must be treated before donation.
Anatomic Evaluation
CT angiography of the abdomen is the gold standard for pre-donation anatomic assessment. This imaging evaluates arterial anatomy, including the number, location, and size of renal arteries, and identifies early branching or accessory arteries. Venous anatomy is assessed for variations such as circumaortic or retroaortic left renal veins and multiple renal veins. The collecting system is examined to rule out ureteropelvic junction obstruction, duplication, or horseshoe kidney. Renal parenchyma is evaluated for cysts (using the Bosniak classification), masses, cortical thinning, calcifications, and stones. The left kidney is generally preferred for laparoscopic nephrectomy because it has a longer renal vein, which facilitates venous anastomosis in the recipient. The right kidney may be donated if the left kidney has superior function, unfavorable anatomy, or multiple left renal arteries.
<image>CT angiography with 3D reconstruction showing bilateral renal vascular anatomy in a living donor candidate: left kidney with single renal artery and long left renal vein crossing anterior to the aorta (preferred for donation), and right kidney with two renal arteries and a short renal vein, with labeled aorta, IVC, renal arteries, renal veins, and ureters for pre-surgical planning</image>
Urolithiasis in Donors
Active bilateral nephrolithiasis is an absolute contraindication to donation. A small, unilateral stone less than 1.5 cm in a donor without metabolic risk factors may be acceptable, and in such cases, the stone-bearing kidney is typically donated if cleared. A metabolic stone workup, including 24-hour urine collection for calcium, oxalate, citrate, uric acid, and cystine, is required. A history of recurrent stones is generally a contraindication.
Psychosocial Evaluation
A mandatory psychosocial assessment is conducted by a social worker or psychologist. This evaluation explores the donor’s motivation for donation, understanding of risks, relationship to the recipient, mental health history, substance use history, social support, and financial impact. Active substance abuse is a contraindication to donation, while a remote history is evaluated on a case-by-case basis. Stable, treated psychiatric conditions are generally acceptable, but active untreated major depression or psychosis is a contraindication. Financial considerations are important because donors may face loss of income during recovery; therefore, resources for donor assistance programs should be provided.
Contraindications to Living Donation
Absolute contraindications include age under 18 years (with some exceptions for emancipated minors in select jurisdictions), uncontrolled hypertension or hypertension requiring more than two medications, diabetes mellitus (type 1 or type 2), eGFR less than 80 mL/min/1.73 m², proteinuria greater than 300 mg/day, active malignancy or insufficient cancer-free interval, HIV infection (except HIV-positive donor to HIV-positive recipient under the HOPE Act), active hepatitis B or C infection (with exceptions for HCV-positive donor to HCV-positive recipient protocols), bilateral nephrolithiasis or recurrent stone disease with metabolic risk, chronic kidney disease of any cause, and active substance abuse.
Relative contraindications include a BMI over 35, prediabetes with additional risk factors, a strong family history of ESRD (particularly a first-degree relative with diabetes-related ESRD), sickle cell trait (which is generally acceptable, whereas sickle cell disease is an absolute contraindication), a single stone without metabolic risk factors (which may proceed with donation of the stone-bearing kidney), and psychiatric comorbidity that is stable and treated.
Donor Surgical Procedure
Laparoscopic Donor Nephrectomy
The standard surgical approach for donor nephrectomy is laparoscopic, typically using three to four ports via a transperitoneal route. The procedure may be hand-assisted or purely laparoscopic. The left kidney is preferred because its longer renal vein facilitates venous anastomosis in the recipient. Key surgical steps include mobilizing the colon, identifying the ureter and gonadal vein, dissecting the renal hilum, clipping and dividing the renal artery and vein, and extracting the kidney through a small Pfannenstiel or periumbilical incision. Operative time generally ranges from two to four hours, with blood loss typically less than 100 mL. Hospital stay is usually two to three days, with donors returning to sedentary work in two to three weeks and resuming full activity in four to six weeks.
Donor Risks and Outcomes
Perioperative mortality is very low, approximately 0.03% (3 in 10,000), comparable to laparoscopic cholecystectomy. Major complications occur in 2-4% of donors and include bleeding requiring transfusion, conversion to open surgery, visceral injury, and thromboembolic events. Minor complications such as wound infection, ileus, and urinary tract infection occur in 5-10% of donors. The long-term risk of ESRD is slightly increased compared to age-matched non-donors but remains very low, with an absolute risk of about 0.5% over 15 years compared to 0.3% in matched controls. The remaining kidney undergoes compensatory hypertrophy, increasing GFR to 70-80% of the pre-donation bilateral GFR within weeks. Long-term eGFR stabilizes at approximately 65-70% of the pre-donation level, with most donors maintaining an eGFR above 60 mL/min. There is a slightly increased long-term risk of hypertension, so annual blood pressure monitoring is recommended. Regarding pregnancy, living donation does not significantly increase the risk of preeclampsia or adverse pregnancy outcomes in most studies, although some data suggest a slightly elevated risk.
<image>Laparoscopic donor nephrectomy port placement diagram showing a left-sided transperitoneal approach with three trocar positions and hand-assist port, intraoperative view of the left renal hilum with labeled renal artery, renal vein with gonadal and adrenal vein branches, ureter, and the kidney being extracted through a Pfannenstiel incision in an endocatch bag</image>
Post-Donation Follow-Up
OPTN/UNOS mandates a two-year follow-up period after donation, which includes clinical assessment, blood pressure measurement, serum creatinine, and urinalysis at six months, one year, and two years post-donation. The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend lifetime follow-up with annual monitoring of blood pressure, serum creatinine, and urine protein. Donors should be counseled on modifiable risk factors such as maintaining a healthy BMI, avoiding nephrotoxic medications like NSAIDs, controlling blood pressure, and ensuring adequate hydration. Living donor registries track long-term outcomes to facilitate quality improvement and research.
Key Clinical Pearls
Donor safety is the absolute priority in living kidney donation because the donor is a healthy individual undergoing elective surgery. Any doubt about donor suitability should lead to declining the donor. Measured GFR, rather than estimated GFR, should be used for donor evaluation since eGFR equations may be inaccurate in healthy individuals with normal muscle mass. The left kidney is preferred for laparoscopic nephrectomy due to its longer renal vein, and the kidney with lesser function or less favorable anatomy is typically donated. Diabetes is an absolute contraindication to living donation, while prediabetes with additional risk factors is a strong relative contraindication. CT angiography is the single most important anatomic study because it defines the vascular anatomy, collecting system, and renal parenchyma in one examination. The independent donor advocate, mandated by OPTN, serves to protect the donor’s autonomous decision-making throughout the process.
References
- Lentine KL, Kasiske BL, Levey AS, et al. KDIGO clinical practice guideline on the evaluation and care of living kidney donors. Transplantation. 2017;101(8S Suppl 1):S1-S109.
- OPTN/UNOS Policy 14: Living Donation. Updated 2023. Available at: https://optn.transplant.hrsa.gov.
- Muzaale AD, Massie AB, Wang MC, et al. Risk of end-stage renal disease following live kidney donation. JAMA. 2014;311(6):579-586.
- Mjoen G, Hallan S, Hartmann A, et al. Long-term risks for kidney donors. Kidney Int. 2014;86(1):162-167.
