Kidney Transplant Fundamentals: Evaluation, Selection, and Surgical Considerations
Learning Objectives
By the end of this module, students will be able to:
- Evaluate potential kidney transplant recipients using current guidelines and contraindication frameworks
- Differentiate between living and deceased donor evaluation and procurement strategies
- Explain HLA matching, crossmatching techniques, and the clinical significance of donor-specific antibodies (DSA)
- Assess patient sensitization using panel reactive antibody (PRA) calculations
- Describe the surgical technique of renal transplantation and immediate post-operative management
- Discuss ABO-incompatible transplantation protocols and outcomes
- Evaluate the impact of kidney donor profile index (KDPI) and estimated post-transplant survival (EPTS) scoring on allocation decisions
- Explain paired kidney exchange programs and their impact on waitlist dynamics
I. TRANSPLANT RECIPIENT EVALUATION
A. General Principles
Kidney transplantation is the renal replacement therapy of choice for eligible ESRD patients, offering superior survival and quality of life compared to dialysis. Comprehensive pretransplant evaluation addresses both transplant candidacy and pretransplant comorbidity optimization.
Key Timeline: Average time from referral to transplantation is 3-6 months for living-related donors, 6-12 months for living unrelated donors, and variable for deceased donors (average wait time now exceeds 5 years nationally in the US).
B. Absolute Contraindications (Relative Assessments Required)
| Contraindication | Rationale | Current Perspective |
|---|---|---|
| Active malignancy | Immunosuppression increases recurrence risk | Transplant most solid malignancies 2-5 years post-cure; some advocate earlier (>2 yr) with close monitoring |
| Active untreated infection | Risk of dissemination on immunosuppression | May proceed if documented sustained negative cultures (e.g., TB) |
| Severe cardiac disease (NYHA IV, uncontrolled arrhythmia) | High perioperative and early graft loss | Cardiac optimization essential; LVEF >30% generally required |
| Expected survival <5 years (non-renal) | Transplant benefit predicated on allograft survival | Individual assessment; many >60 yr successfully transplanted |
| Psychosocial inability to comply | Immunosuppression adherence critical | Pre-transplant psychosocial evaluation and support essential |
| Active substance abuse | Compliance and allograft injury risk | Minimum 6-12 months sobriety generally required |
C. Relative Contraindications and Optimization
Age: No absolute upper age limit; outcomes in carefully selected octogenarians are favorable.
Obesity: BMI >40 kg/m² carries increased surgical and metabolic morbidity. Pretransplant weight loss (goal: BMI <35) recommended.
Diabetes: Requires intensive glycemic control; HbA1c >8.5% warrants delay for optimization.
Cardiovascular disease: Stress testing (dobutamine echo or nuclear) recommended if >5 risk factors or prior events. Coronary angiography considered based on symptomatology and functional capacity.
Chronic infections: - Hepatitis C: Now may be transplanted with DAA therapy planned pre- or post-transplant - Hepatitis B: Vaccination or prophylaxis strategies deployed; HBsAg+ patients transplanted with antiviral therapy - HIV: CD4 >200 cells/μL, undetectable viral load, and ART adherence required
Renal disease recurrence: Patients with FSGS, IgA nephropathy, membranoproliferative GN, and hemolytic uremic syndrome (HUS) have variable recurrence but are generally not absolute contraindications.
II. DONOR EVALUATION AND SELECTION
A. Living Donor Evaluation
Living donor kidneys provide superior long-term outcomes compared to deceased donor kidneys, with 10-year graft survival rates of 60-70% vs. 45-55%.
Medical Evaluation Components:
- Renal function assessment:
- Serum creatinine and calculated GFR (KDIGO preferred)
- Baseline proteinuria (<150 mg/day acceptable)
- Absence of hypertension or controlled BP on ≤1 agent
- Cardiovascular screening:
- HTN, DM, CAD risk stratification
- Stress testing if significant risk profile
- Goal: preserve donor long-term health
- Metabolic assessment:
- Glucose tolerance; DM is contraindication
- Lipid panel
- Bone health (DEXA scan if risk factors)
- Infectious disease screening:
- HIV, HBsAg, anti-HBc, anti-HCV, RPR, CMV IgG, EBV IgG
- Additional testing for endemic regions (Chagas, TB)
- Imaging:
- Renal ultrasound (assess size, exclude masses)
- Renal artery duplex (multiple vessels increase surgical complexity)
- Consider CT angiography for anatomic variants
- Psychological and social assessment:
- Verify informed consent, understand risks and life expectancy reduction
- Screen for coercion, financial inducement
- Ensure appropriate expectations regarding recipient outcomes
Living Donor Outcome Data: Donors have slightly elevated risk of ESRD (RR ~1.5-2.0 compared to general population) but maintain excellent quality of life with one kidney; lifespan unchanged.
B. Deceased Donor Evaluation
Standard Criteria Donors (SCD): Age <50 years, absence of significant HTN/DM, SCr <1.5 mg/dL.
Expanded Criteria Donors (ECD): Age ≥50 years OR (age 40-49 AND serum creatinine >1.5 mg/dL) OR history of hypertension or diabetes.
Donation After Cardiac Death (DCD): Donor support withdrawn after cardiac arrest; kidneys procured during ischemic time. Associated with higher delayed graft function (DGF) rates (~50%) but good long-term outcomes.
Donor Risk Assessment: - Donor age and comorbidities (HTN, DM, CVD history) - Cause of death (trauma, stroke, anoxia) - Donor renal reserve and biopsy findings (if obtained)
Key Laboratory Parameters: - Serum creatinine (baseline renal function proxy) - BUN, electrolytes - Liver function (assess organ integrity) - Blood cultures, serologies, toxicology
III. IMMUNOLOGICAL COMPATIBILITY ASSESSMENT
A. ABO Blood Group
Basis: Natural IgM antibodies against incompatible blood group antigens present from infancy.
| ABO Type | Can Donate To | Can Receive From |
|---|---|---|
| O | O, A, B, AB | O |
| A | A, AB | O, A |
| B | B, AB | O, B |
| AB | AB | O, A, B, AB |
ABO-Identical transplantation offers superior outcomes; ABO-compatible grafts function well with modern immunosuppression.
B. HLA Typing and Matching
HLA System: Human leukocyte antigens (HLA) present on all nucleated cells; major targets of adaptive immune response against allograft.
HLA Loci Tested: HLA Class I (A, B, C) and Class II (DR, DQ, DP).
HLA Matching Grade:
| Mismatch | Description | Impact |
|---|---|---|
| 0-ABDR | Identical (rare) | Best outcomes; lowest rejection |
| 1-2 ABDR | Well-matched | Excellent outcomes |
| 5-6 ABDR | Fully mismatched | Acceptable with modern IS; requires close monitoring |
Clinical Significance: With modern immunosuppression, HLA mismatch burden has diminished but remains relevant for long-term graft survival. Zero-mismatch grafts have superior 10-year survival.
C. Crossmatching
Complement-Dependent Cytotoxicity (CDC) Crossmatch: - Traditional method; detects recipient IgG antibodies binding donor lymphocytes - Positive crossmatch = contraindication to transplant in standard practice
Flow Cytometry Crossmatch: - More sensitive; detects weak IgG and IgM antibodies - Used to refine CDC-negative cases
Luminex Single Antigen (SAB) Beads: - Identifies specific HLA antibodies against donor antigens - Detects donor-specific antibodies (DSA) - Gold standard for contemporary pretransplant assessment
HLA Antibody Definitions:
| Category | Significance |
|---|---|
| Donor-Specific Antibodies (DSA) | IgG antibodies targeting donor HLA antigens; major risk factor for rejection |
| Non-Donor-Specific Antibodies (non-DSA) | IgG to HLA antigens not on donor; lesser threat but may contribute to chronic inflammation |
| Class I DSA | Target HLA-A, -B, -C; associated with antibody-mediated rejection (AMR) and chronic AMR |
| Class II DSA | Target HLA-DR, -DQ, -DP; emerging evidence of independent risk for AMR and graft loss |
D. Panel Reactive Antibody (PRA) and Sensitization
Definition: Percentage of population against which recipient has detectable IgG antibodies.
Calculation: - Percentage of panel cells bearing HLA antigens recognized by recipient serum - PRA >10-20% considered sensitized; impacts urgency allocation and transplant access
Clinical Impact: - Highly sensitized patients (PRA >80%) have limited compatible donors; spend extended time on waitlist - Sensitization from prior transplants, transfusions, pregnancy, or dialysis transfusions - Requires compatible or ABO-incompatible transplant protocols
Mean Fluorescence Intensity (MFI): - Quantifies DSA strength via Luminex - MFI >1000-2000 considered significant risk for hyperacute or acute rejection - Used to risk-stratify transplant candidates
IV. SURGICAL TECHNIQUE AND IMMEDIATE POST-OPERATIVE MANAGEMENT
A. Surgical Approach
Standard Procedure: 1. Incision: Heterotopic placement in iliac fossa (Gibson incision), not replacing native kidneys 2. Vascular anastomosis: Donor renal artery to internal iliac (or external iliac) artery; renal vein to external iliac vein 3. Ureteral anastomosis: Ureteroureterostomy (to native ureter) or ureteroneocystostomy (to bladder); most commonly ureteroneocystostomy 4. Native kidneys: Left in place unless infected, causing hypertension, or polycystic disease
Surgical Considerations: - Ischemic time (cold ischemia time, CIT) impacts DGF risk; <20 hr ideal, <30 hr acceptable - Warm ischemia time during vascular anastomosis kept minimal - Arterial and venous complications (thrombosis, stenosis) occur in 1-3% of cases
B. Immediate Post-Operative Management (First 24-48 Hours)
Graft Function Monitoring: - Hourly urine output (expect 100-200+ mL/hr initially) - Serum creatinine decline (ideal: 10-25% daily drop if DGF not present) - Ultrasound with Doppler: assess perfusion, exclude fluid collections, evaluate ureter
Delayed Graft Function (DGF): - Defined as need for dialysis in first post-op week - Occurs in 15-25% of deceased donor, 5% of living donor transplants - Managed conservatively with fluid management and dialysis; does not necessarily indicate graft loss - Monitor for hyperkalemia, acidosis, volume overload
Immunosuppression Initiation: - Induction agents started intraoperatively or immediately post-op - Maintenance agents initiated (tacrolimus, mycophenolate, prednisone typically) - Dosing adjusted for renal function and drug levels
Fluid and Electrolyte Management: - Goal: euvolemia; CVP 5-10 cm H₂O - Aggressive hydration in first 24-48 hr supports urine output and graft perfusion - Monitor potassium, phosphate, magnesium closely - Acidosis correction if pH <7.2
Prophylaxis: - Antibiotic: single-dose prophylaxis (cephalosporin, fluoroquinolone) - CMV prophylaxis (valganciclovir) if donor/recipient mismatch (D+/R- highest risk) - PCP prophylaxis (TMP-SMX) started day 1 if sulfa-tolerant
V. ABO-INCOMPATIBLE TRANSPLANTATION
A. Background and Rationale
ABO-incompatible (ABOi) transplantation overcomes blood group incompatibility through desensitization, expanding donor pool and reducing waitlist times. Living related ABOi grafts historically had ~50% 3-year survival; modern protocols achieve >90% 1-year and 70-80% 5-year graft survival.
B. Desensitization Strategies
Plasmapheresis-Based Protocols: - Plasma exchange to remove IgG isohemagglutinins (target: titer <1:4 or <1:8) - Performed 3-5 times in week preceding transplant - Goal: reduction of IgG to donor ABO antigen
Immunoadsorption Columns: - ABO antigen-coated columns selectively remove anti-ABO IgG - More efficient than plasmapheresis; allows same-day transplant in some protocols
Splenectomy: - Historically performed; rationale is to remove antibody-producing B cells - Current protocols often omit splenectomy; not essential with modern IS
Low-Titer Protocols: - Single-donor immunoglobulin (IVIG), rituximab, and minimalist plasmapheresis - Reducing procedural burden while maintaining excellent outcomes - Requires careful titer monitoring (target IgG <1:4 pre-op)
C. Post-Transplant Management
Monitoring: - ABO antibody titers at regular intervals post-op - Rejection surveillance with protocol biopsies in early period - Graft function trending
Prevention of Hyperacute Rejection: - Induction therapy with T-cell (ATG, thymoglobulin) or B-cell (rituximab) agents - Tacrolimus-based maintenance with goal trough 8-12 ng/mL - Mycophenolate and corticosteroids
Outcomes: Modern ABOi protocols achieve graft survival comparable to ABO-compatible grafts when desensitization is successful.
VI. PAIRED KIDNEY EXCHANGE PROGRAMS
A. Concept and Mechanics
Problem: Incompatible living donor-recipient pairs (ABO incompatible, crossmatch-positive, or HLA sensitized) previously had limited transplant options.
Solution: Paired kidney exchange (PKE) matches incompatible pairs with other incompatible pairs, creating mutually compatible swaps.
Example: - Pair 1: Recipient A (O blood type) with Donor B (AB blood type) — incompatible - Pair 2: Recipient B (AB blood type) with Donor A (O blood type) — incompatible - Solution: Swap donors; both recipients receive compatible kidneys
B. Extended Matching Chains
Desirable Donor (DD) Chain: Initiated by altruistic non-directed donor (NDD); chains of swaps continue until an incompatible pair “closes” the chain by providing a kidney to the national waiting list.
Bridge Donor Chain: Similarly initiated but require closure differently.
National Kidney Registry: Facilitates multi-center coordination; 6-way, 8-way, and larger exchanges documented.
C. Impact and Outcomes
Benefits: - Reduces waiting time for incompatible pairs - Increases access to living donor transplantation - Improves HLA matching opportunities (paradoxically, exchange participants often achieve zero mismatches) - Equivalent outcomes to standard living donor transplants
Logistics: Synchronized surgeries (often at multiple centers) ensure fairness and prevent exploitation.
Ethical Considerations: Strict non-coercion protocols; thorough informed consent; altruistic donation encouraged.
VII. KDPI AND EPTS SCORING
A. Kidney Donor Profile Index (KDPI)
Definition: Percentage likelihood that a deceased donor’s kidney(s) will fail before a reference kidney from an average donor.
Formula: Incorporates donor age, height, weight, race/ethnicity, history of hypertension, history of diabetes, cause of death (cerebrovascular vs. other), and serum creatinine.
| KDPI Range | Interpretation | Clinical Application |
|---|---|---|
| 0-20% | Excellent donor | Allocated to younger recipients (EPTS <20%) in new allocation system |
| 21-35% | Very good | Flexible allocation |
| 36-50% | Good | Acceptable for most recipients |
| 51-80% | Marginal | Expanded criteria donors; acceptable for older/sicker recipients |
| 81-100% | Poor** | Very marginal; consider in highly sensitized or long-waitlist patients |
Clinical Significance: KDPI is predictor of graft survival; lower KDPI (better donor quality) allocated preferentially to younger, healthier recipients expected to have longer life expectancy.
B. Estimated Post-Transplant Survival (EPTS)
Definition: Percentage likelihood that a recipient will survive for at least 20 years after transplantation.
Factors: Age, dialysis vintage, BMI, diabetes status, prior transplant history.
| EPTS Range | Interpretation | Clinical Application |
|---|---|---|
| 0-20% | Excellent survival expected | Prioritized to receive best-quality kidneys (KDPI <20%) |
| 21-35% | Very good survival expected | Standard allocation |
| 36-50% | Good survival expected | Flexible allocation |
| 51-100% | Limited survival expected | Allocated marginal kidneys (KDPI >80%) or in-region priority |
Allocation Impact: KDPI/EPTS matching system implemented 2015 by UNOS aims to maximize overall life-years gained from the donor pool by pairing best donors with longest-living recipients and marginal donors with shorter-living recipients.
Controversy: System benefits younger, healthier recipients; may disadvantage older/sicker dialysis patients but optimizes population-level outcomes.
VIII. CLINICAL PEARLS
Pre-transplant optimization is essential: Ensure excellent glycemic control (HbA1c <7%), blood pressure control, cardiac assessment, and dental care before transplantation.
Living donor kidneys are superior: Encourage living donation; develop a strong living donation education program in your practice.
Crossmatch interpretation requires context: CDC-negative/SAB-positive (donor-specific antibody with negative CDC crossmatch) may be acceptable in modern protocols with desensitization; discuss with immunology.
DGF is common in deceased donor transplants but not catastrophic: 80-90% of DGF kidneys achieve excellent long-term function; manage expectantly with dialysis support.
ABO incompatibility is not absolute: Modern desensitization protocols achieve excellent outcomes; expand donor pool when appropriate.
KDPI/EPTS matching optimizes population-level outcomes: Accept that marginal kidneys in older recipients may provide net benefit; discuss realistic expectations.
Surgical anatomy varies: Multiple renal arteries (20%), early branching, and retroaortic/circumaortic positioning require imaging review to minimize vascular complications.
Native kidneys are retained: Unless chronically infected, severely hypertensive, polycystic, or causing other complications.
Transplant benefit begins at referral: Shorter dialysis vintage correlates with superior outcomes; refer early (when GFR 15-20 mL/min/1.73 m²).
Transplant is superior to dialysis: At any age, transplant offers superior survival, quality of life, and cost-effectiveness vs. long-term dialysis.
IX. PRACTICE QUESTIONS
Question 1: A 68-year-old man with ESRD from hypertensive nephrosclerosis presents for transplant evaluation. He has controlled hypertension on one agent, no diabetes, normal BMI, and recent normal stress test. His living brother (age 62) offers to donate. Pretransplant evaluation of the living donor reveals: - Serum creatinine 1.1 mg/dL, calculated GFR 65 mL/min/1.73 m² - BP 135/80 on no medications - No proteinuria - Normal imaging - Willing and psychologically cleared
Is this living donor appropriate?
- No, because he is >60 years old
- Yes, with counseling regarding his baseline renal function and age
- No, because his GFR is <70 mL/min/1.73 m²
- Yes, but only if the recipient undergoes splenectomy
Answer: B. Age alone is not a contraindication; this donor meets criteria with acceptable renal function (GFR 65), normal BP on no medications, and no proteinuria. Counseling should address his baseline GFR and slight age-related renal function decline post-donation but is not prohibitive.
Question 2: A 35-year-old dialysis patient with prior failed transplant (failed 8 years ago from chronic rejection) is being reevaluated for transplant. Current sensitization: - Class I PRA 40%, Class II PRA 25% - Luminex SAB reveals multiple high-MFI class I and class II DSA from prior graft - Wants to move forward with transplant
Which statement is most accurate regarding this candidate’s sensitization?
- He should remain on dialysis indefinitely due to high sensitization
- He is a candidate for desensitization and/or compatible paired exchange
- He requires splenectomy before any transplant can be performed
- His prior rejection history is an absolute contraindication to retransplantation
Answer: B. This patient is sensitized (PRA >30%) but not an absolute contraindication. Desensitization protocols (plasmapheresis, IVIG, rituximab) and/or paired kidney exchange programs can expand his donor pool. Prior transplant failure is not absolute contraindication to retransplant, especially with modern immunosuppression.
Question 3: A deceased donor kidney has KDPI 85%. The two potential recipients are: - Recipient A: 45 years old, EPTS 15%, 2 years on dialysis - Recipient B: 72 years old, EPTS 75%, 5 years on dialysis
According to current UNOS allocation policy, which recipient should receive priority?
- Recipient A, because he is younger
- Recipient B, because he is older and has fewer remaining years
- The kidney should not be transplanted due to high KDPI
- Recipient B, because KDPI/EPTS matching indicates marginal kidneys should go to recipients with limited survival
Answer: D. This high-KDPI (85%) marginal donor kidney should be allocated to the recipient with limited expected post-transplant survival (Recipient B, EPTS 75%) to maximize overall life-years gained. Recipient A with excellent EPTS (15%) should be reserved for better-quality kidneys (lower KDPI).
See Also
Clinical Content (01-Clinical-Medicine/Nephrology)
- Kidney Transplantation Hub
- Essential Renal Laboratory Tests
Butler-COM Resources
- Butler COM - Nephrology Deep Dive
X. REFERENCES
Wolfe RA, Ashby VB, Milford EL, et al. Comparison of mortality in all patients on dialysis, patients on dialysis awaiting transplantation, and recipients of a first cadaveric transplant. N Engl J Med. 1999;341(23):1725-1730.
Terasaki PI, Cecka JM. Organ transplantation, immunity and clinical practice. Lancet. 1997;350(9087):1320-1321.
KDIGO Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2013;3(Suppl):1-150.
Orandi BJ, Utter GH, Redd A, et al. Kidney paired donation with extended criteria donors. N Engl J Med. 2019;380(3):252-262.
Zachary AA, Montgomery RA. Transplantation across desensitization: HLA and non-HLA antibody reduction. Curr Opin Organ Transplant. 2016;21(4):433-438.
Taber DJ, Srinivas TR, Egidi MF, et al. Influence of donor-specific antibodies on acute rejection and graft survival in primary renal transplant recipients. Transplant Rev (Orlando). 2015;29(4):225-230.
Roodnat JI, Mulder PG, Zietse R, et al. Protection against chronic renal allograft dysfunction by suboptimal HLA matching in highly sensitized renal transplant recipients. Transplantation. 2001;72(5):813-819.
Oderup C, Ekdahl KN, Sehgal G, et al. Platelet activation and thromboinflammation in cardiac transplant rejection. Transplantation. 2017;101(3):497-508.
Colvin RB, Smith RN. Antibody-mediated organ-allograft rejection. Nat Rev Immunol. 2005;5(10):807-817.
Montgomery RA, Lonze BE, King KE, et al. Desensitization in HLA-incompatible kidney recipients and survival. N Engl J Med. 2011;365(4):318-326.
Roodnat JI, Kal JA, Mathot RA, et al. Kidney graft failure in the cooperative study on the effect of HLA matching on long-term renal allograft survival. Transplantation. 2003;76(8):1169-1172.
Weckerle A, Sieg A, Bartlett RH, et al. The history of organ transplantation. JAMA Surg. 2020;155(1):74-75.
Clinical Resources
- Clinical Review: Immunosuppression Transplant Review — Comprehensive clinical review with PubMed references