Kidney Transplant Outcomes, Donor & Recipient Factors

Learning Objectives

Understand outcome differences between:
- Living-donor kidneys
- Sub-types of deceased-donor kidneys (standard, DCD, high KDPI, AKI, etc.)
Recognize the risks and benefits of transplanting kidneys with high Kidney Donor Profile Index (KDPI)

Graft Survival
- Defined as the earliest occurrence of death, re-transplantation, or return to dialysis.
Half-life of a transplant
- Time at which 50\% of grafts that have survived >1\,\text{yr} are still functioning.
Delayed Graft Function (DGF)
- Need for dialysis in the first 7 post-operative days; simultaneously an outcome and a risk factor.

One-year graft survival
- Living donors: >98\%
- Deceased donors (overall): >94\%; varies by donor quality.
Projected half-lives
- Living donors: >15\,\text{yr}
- Deceased donors: >11\,\text{yr}
Key determinant: donor factors weigh more heavily than recipient factors.
Improvement drivers over decades:
- Better peri- & post-operative care
- Refined donor/recipient selection
- Regulatory oversight emphasizing post-transplant outcomes

One-year patient survival
- Living donors: >99\%
- Deceased donors: >96\%
Key determinant: recipient factors (especially age) outweigh donor factors.
Age-stratified graphs show older recipients have lower survival but still gain benefit vs. dialysis.
Both short- and long-term patient survival continue to rise with advancing medical care.

All transplant recipients gain life-years & quality of life (QOL) compared with remaining on dialysis.
Greatest incremental benefit when:
- Recipient has high baseline survival expectancy (younger, fewer comorbidities).
- Kidney is of higher quality (low KDPI, living donor).
Relative-risk curve:
- Peri-operative period: transiently higher mortality than waiting list.
- Time-to-equal risk & time-to-equal survival vary by donor/recipient profile; beyond that point, transplant always superior.

EPTS (Estimated Post-Transplant Survival)
- Inputs: age, dialysis time, diabetes, re-transplant status.
- Candidates with \text{EPTS}=0\text{–}20\% get priority for \text{KDPI}=0\text{–}20\% kidneys.
Additional recipient variables captured by SRTR models (selected list):
- Sex, race, BMI, cardiovascular disease, cause of ESRD, serum albumin, history of malignancy, hospitalization status, etc.
Age-related observations:
- ↑ age ⇒ ↓ acute rejection, ↑ adherence
- But also ↑ readmission, ↑ malignancy, ↑ cost
Sensitization
- Panel Reactive Antibody (PRA) less predictive than Donor-Specific Antibody (DSA) in modern assays.
- Highly sensitized patients benefit from: paired donation, national organ sharing, desensitization protocols.
Important but unmodeled factors (data limitations): cardiovascular status, psychosocial issues, frailty/functional status.

KDPI (Kidney Donor Profile Index) – scaled 1\text{–}100\%; incorporates:
- Age, ethnicity, cause of death, serum creatinine, DCD status, HTN, DM, height, weight, HCV.
KDRI (Kidney Donor Risk Index) – continuous (not rescaled); adds factors only known later:
- Cold-ischemia time, dual/en-bloc use, HLA-B/DR mismatch.
Allocation rules:
- \text{KDPI}=0\text{–}20\% ➔ offered to \text{EPTS}=0\text{–}20\% candidates first.
- \text{KDPI}=0\text{–}35\% ➔ pediatric priority.
- >85\% ➔ only to candidates who pre-consent.
High KDPI Kidney Outcomes
- All KDPI strata (even >85\%) confer survival advantage over continued dialysis.
- Time-to-equal survival lengthens as KDPI rises.
- Subgroups with pronounced benefit: age >50, diabetes, center wait time >33\,\text{months}.

Donation after Cardiac Death (DCD)
- Unadjusted graft & patient survival ≈ brain-dead donors (DBD).
- Adjusted graft survival slightly lower; higher DGF risk.
- Interaction: older & high-KDPI DCD kidneys carry more graft-failure risk than same-profile DBD.
Acute Kidney Injury (AKI) Donors
- Outcomes mirror DCD: equivalent adjusted survival, ↑ DGF.
- Paradox: lesser degrees of AKI + DGF may harm graft survival more than severe AKI.
Dual/En-Bloc Transplants
- Indications: very high KDPI (up to 100\%) or pediatric donors as small as 5\,\text{kg}.
- Dual kidneys ➔ graft survival comparable to standard single kidneys; superior to single kidney from same donor profile.
- Usage thresholds vary: 10\text{–}20\,\text{kg} (pediatric) or \text{KDPI}=90\text{–}100\% (adult).

Derived metric parallels deceased-KDPI; overlapping quality ranges.
Risk contributors: age, BMI, African-American race, prior smoking, systolic BP, male‐to-male donation, weight ratio, ABO incompatibility, unrelated donor-recipient, HLA-B/DR mismatch.

Donor risk factors: AKI, DCD, high KDPI, prolonged cold ischemia.
Recipient risk factors: older age, larger body size, Black race, high PRA, diabetes, high BMI, cardiovascular disease.
Consequences:
- ↑ acute rejection
- ↑ graft loss
Nomogram exists for individualized DGF risk prediction.

Uses continuous perfusion for evaluation and therapy.
Benefits (observational): ↓ DGF, no change in graft failure.
Randomized trials: ↓ DGF and improved graft survival.
Resistance to pump flow inversely correlates with graft survival (high resistance ⇒ worse outcome).

Widely performed; increases risk of discard.
Heterogeneity in technique/interpretation limits evidence.
Overall, biopsied kidneys have slightly worse survival – may reflect selection bias.
Findings & impact:
- Glomerulosclerosis >20\% ⇒ modest ↓ graft survival.
- Composite scores (interstitial fibrosis, arteriosclerosis) show stronger predictive value in single-center data.
Ongoing efforts: standardize biopsy method & centralize pathology to boost utilization.

Kidney transplant outcomes have steadily improved; current 1-yr patient survival approaches 100\% for living donors.
Donor quality is the primary determinant of graft survival; recipient age & comorbidities chiefly drive patient survival.
Even high KDPI kidneys yield a survival advantage over dialysis; decision hinges on local wait time and individual risk.
DCD and AKI donors expand the pool with acceptable outcomes but demand strategies to mitigate DGF.
Tools/indices (EPTS, KDPI, KDRI, living-KDPI, DGF nomograms) facilitate nuanced matching, yet unmeasured factors (frailty, psychosocial health) remain important in clinical judgment.