Kidney Donor Comparison: 75-Year-Old Mother (Same Blood Group) vs. Wife (Different Blood Group)

Bottom Line

1. Why Donor Age Matters So Much

"Older kidney donor age is associated with reduced kidney transplant survival. A donor age effect is apparent among deceased and living donor transplants. These results are thought to reflect a higher incidence of delayed graft function (DGF) and of nephron 'underdosing.' Allografts from older donors have fewer functioning nephrons because of the aging process and donor-related conditions such as hypertension and atherosclerosis."

• Graft survival was significantly higher in recipients of kidneys from donors aged <60 vs. >60.
• Risk of acute rejection was lower (RR 0.62, 95% CI 0.5-0.8) with younger donors.
• Risk of delayed graft function was dramatically lower (RR 0.28, 95% CI 0.1-0.9) with younger donors.
• 1-year serum creatinine was significantly lower with donors <60 years.

• GFR declines at ~9 mL/min/1.73 m² per decade after age 40
• The donated kidney starts with a reduced nephron reserve
• Risk of DGF, faster progression of chronic allograft nephropathy, and shorter graft longevity are all substantially elevated

2. ABO Incompatibility - A Manageable Barrier

"ABO-incompatible protocols now mostly entail a relatively short but intensive pretransplant regimen consisting of rituximab, IVIg, and plasmapheresis - continued until anti-A/B titers fall below a prespecified safe threshold (usually 1:8 or 1:16)... The long-term outcome of desensitized recipients of blood group incompatible organs is good although perhaps slightly inferior to that of ABO-compatible kidney transplant recipients, much of the excess risk being concentrated in the early post-transplant period."

• Short- to mid-term patient and graft survival in ABO-incompatible living donor kidney transplant (ABOi-LDKT) was comparable to ABO-compatible transplants in modern cohorts with desensitization.
• No significant difference in DGF, acute rejection, or surgical complications.
• Main downside: higher hospitalization costs due to desensitization procedures.

3. Head-to-Head Comparison

4. Practical Considerations

1. Paired/Chain Exchange Programs: Before desensitizing, check if the wife can enter a kidney paired exchange program - she donates to a compatible recipient, and the patient gets a compatible kidney from another donor. This avoids desensitization entirely and may yield an even better-matched organ.
2. Anti-A/B Titer of Wife: If the recipient's anti-A/B titer is already low (e.g., A2 blood group donor into a B recipient), desensitization may be minimal or unnecessary.
3. HLA Matching: The mother, being a first-degree relative, may have better HLA matching. The wife may have no HLA sharing. However, with modern immunosuppression, HLA mismatch is much less impactful than donor age on outcomes.
4. Mother's Candidacy at 75: Most international guidelines and centers would carefully scrutinize or decline a 75-year-old donor due to reduced functional reserve. The donor evaluation (GFR, cardiovascular status, proteinuria, imaging) would need to be thorough.
5. KDIGO 2017 Living Donor Guidelines recommend against advanced-age donors with significant comorbidities, and a 75-year-old is at minimum a high-risk donor.

Summary

Sources: Brenner and Rector's The Kidney, p. 2977-2997; NKF Primer on Kidney Diseases 8e, p. 566-571; Bellini MI et al., J Nephrol 2022 [PMID 35072936]; Chen Y et al., Front Immunol 2026 [PMID 41782862]