The goals of this study are:

• To optimize and evaluate multiple kidney MRI methods; and
• To investigate the potential of MRI in the assessment of transplant kidney functions; To achieve these goals, we will perform pilot MRI studies with kidney transplant patients. We will study if MRI can reflect different levels of kidney function. The investigators will also evaluate if MRI can differentiate causes for declining kidney function. Finally, the investigators will explore how MRI measures changes before and after medical treatment for worsening kidney function.

You may be invited for MRI exams with different exam options. An MRI exam may use either of two types of MRI machines at the center for magnetic resonance research (CMRR): the 3 Tesla (3T) scanner and the 7 Tesla (7T) scanner. You may also be invited for a multi-session exam. A description of the MRI exam types with different exam options and the types of multi-session exams is provided later in this document.

To achieve these goals, the investigators will perform pilot MRI studies with kidney transplant patients. The investigators will study if MRI can reflect different levels of kidney function. The investigators will also evaluate if MRI can differentiate causes for declining kidney function. Finally, the investigators will explore how MRI measures changes before and after medical treatment for worsening kidney function.

Subjects may be invited for MRI exams with different exam options. An MRI exam may use either of two types of MRI machines at the CMRR: the 3T scanner and the 7T scanner. Subjects may also be invited for a multi-session exam. A description of the MRI exam types with different exam options and the types of multi-session exams is provided later in this document.

Inclusion Criteria:

• Renal Transplant Recipients
• Capable to consent
• English speaking
• For studies with patients with fast worsening renal function: An abrupt (within 48 h) reduction in kidney function currently defined as a percentage increase in serum creatinine of ≥50% (1.5-fold from baseline), or a reduction in urine output (documented oliguria of less than 0.5 mL/kg/h for more than 6 h).
• For patients with recovered renal allograft function after therapy: renal allograft function as measured by glomerular filtration rate (eGRF) has been recovered and stabilized above a clinical acceptable level, such as 15 ml/min/1.73 mm2.

Exclusion Criteria:

• On dialysis due to renal allograft failure
• Acute and chronic pulmonary disease
• Pregnancy as reported in CMRR Safety Screen
• Ferromagnetic implants
• Any foreign metal objects in the body
• History of shrapnel or shot gun injury
• Cardiac pacemakers
• Defibrillator
• Neuronal stimulator
• Magnetic aneurysm clip
• Large tattoos on the abdomen or the brain and neck, as determined by CMRR Safety Officer
• Hip replacement
• Too large to fit in the magnet (BMI >= 40, approx.)
• Severe claustrophobia

The proposed studies are pilot studies to obtain preliminary data for the development of hypotheses and estimate the power for future large-scale studies. To accomplish the objectives of the proposed pilot studies, we will enroll a total of 140 renal transplant patients. Based on our previous experience, there will be about 20% patients who may withdraw after informed consent. Equal number of male and female subjects will be recruited for each patient group. In addition, the age of patients will be matched or ensured insignificant across the groups of the study objectives.