Renal Allograft Fibrosis Study

Inclusion Criteria: * Patients post renal transplantation, with acute or chronic allograft dysfunction, referred for biopsy based on clinical grounds (indication biopsy). Patients with be considered to have allograft dysfunction if: 1. Patients will be considered to have acute allograft dysfunction if there is a 15% decline in eGFR or a 0.3-mg/dL increase in sCr level, with laboratory and clinical findings that exclude pre-renal or post-renal dysfunction. 2. Patients will be considered to have chronic allograft dysfunction if there is a sustained \>50% increase in sCr/decrease in eGFR (over their post-transplant nadir creatinine), occurring over a period of \>3 months, with laboratory and clinical findings that exclude pre-renal or post-renal dysfunction. * Patients with stable allograft function and donor-specific antibody (DSA) positivity, referred for surveillance biopsy at 3 and 12 months post transplantation. Patients with be considered to have stable allograft function if: 1. Patients will be considered to have chronic stable allograft function if they have a stable eGFR \> 45 ml/min \& a spot urine protein:creatinine ratio \< 0.2; 2. Stable creatinine/eGFR (i.e. \<25% change in serum creatinine (Cr) and/or eGFR from post transplant baseline). * Patient is able to give informed consent for this study. * Study team will recruit patients after 1 month post-transplant period since the early post transplant course is associated with increased risk of acute dysfunction (i.e. acute tubular necrosis or acute rejection episodes). * Healthy volunteers with no renal disease will be recruited for protocol optimization and to serve as controls. * Potential renal donors undergoing clinical non-contrast or contrast-enhanced MRI will be recruited to serve as controls. Exclusion Criteria: * Age less than 18 years. * Renal transplantation \<1 month prior to scanning. * Evidence of large vessel or urinary tract complication of the renal transplant. * Unable or unwilling to give informed consent. * Contra-indications to MRI 1. Electrical implants such as cardiac pacemakers or perfusion pumps. 2. Ferromagnetic implants such as aneurysm clips, surgical clips, prostheses, artificial hearts, valves with steel parts, metal fragments, shrapnel, tattoos near the eye, or steel implants. 3. Ferromagnetic objects such as jewelry or metal clips in clothing. 4. Pregnant subjects. 5. Pre-existing medical conditions including a likelihood of developing seizures or claustrophobic reactions. The inclusion and exclusion criteria are identical at ISMMS and WCMC. * Screening for eligibility will be performed by the transplant nephrology team at both centers. Data relevant to eligibility will be reviewed, including age, presence of allograft dysfunction and its ascertainment (clinical, laboratory and prior biopsy data), and MRI safety will also be reviewed by the study coordinator. * There are no exclusions based on race, sex/gender, preferred language.