The selection of kidneys from living donors is based on strict glomerular filtration rate (GFR) values, in the setting of the increasing proportion of older donors. The 2017 KDIGO recommendations consider that approving kidney donation for a donor with a GFR between 60 and 89 mL/min/1.73 m² should be individually discussed, possibly using a calculator. A GFR < 60 mL/min/1.73 m² should contraindicate donation without considering the donor's age.

GFR physiologically decreases with age, so older donors frequently have a GFR below 90 ml/min/1.73 m². However, the proportion of older donors continues to rise.

Kidney grafts from older living donors maintain better renal function than those from deceased donors, aiming to counteract the organ shortage.

Kidneys possess functional reserves, allowing an increase in GFR during stimulations and adaptation to reduced functional nephron count (as after nephrectomy). Assessing this adaptive capacity clinically is challenging. It might be dependent on vascularization and/or absence of fibrosis, but these parameters are poorly understood due to a lack of current in vivo exploration methods.

The development of functional renal MRI enables the evaluation of these parameters, allowing measurements on separate, regional, non-invasive, quantitative kidney segments coupled with morphological studies. BOLD-MRI can measure regional oxygen content, thus accessing more precise medullary data. The DWI sequence can estimate renal microstructure and study interstitial fibrosis.

Therefore, evaluating renal performance (by measuring GFR, renal perfusion, fibrosis, inflammation, and oxygen content) in donors, and studying the evolution of these parameters in recipients and donors, could optimize donor selection.

Hence, the aim of our study is to 1) investigate the evolution of renal functional parameters in the transplanted kidney up to 1 year post-transplant, and 2) study the evolution of these same parameters in the contralateral kidney of the donor.

Inclusion Criteria:

For recipients:

• Patients with end-stage chronic kidney disease awaiting kidney transplant from a living donor.
• Adult patient
• Consent signed
• effective contraceptive method for women
• Patient affiliated to a social security or beneficiaries of a similar scheme

For donors:

• Individuals eligible for living kidney donation with GFR > 60 mL/min/1.73 m².
• Adult patient
• Consent signed
• effective contraceptive method for women
• Patient affiliated to a social security or beneficiaries of a similar scheme

Exclusion Criteria:

For the two groups :

• MRI contraindications (claustrophobia, pacemaker, cardioverter defibrillators implantable, mechanical heart valve non MRI-compatible)
• Weight> 130 kg
• Pregnant, parturient or breastfeeding
• Persons deprived of their liberty by a judicial or administrative decision,
• Adults subject to a legal protection measure (safeguard measure, guardianship, curators)
• subject participating in another research including an exclusion period still in progress at inclusion

For recipients :

- Contraindication to renal graft biopsy (ongoing or uninterrupted anticoagulant or antiplatelet treatment, thrombocytopenia <100 x 10^9/L, anemia <7 g/dL).