The goal of this observational study is to learn if PRAT thickness is a marker of visceral obesity and its influence on donors' kidney function and blood pressure in living kidney donors. Population includes male/female, 18 years and up, living kidney donors scheduled for nephrectomy within 6 months. The main area it aims to help in, is future care managing blood pressure and obesity in living kidney transplant donors.

Primary Hypothesis: We hypothesize that Perirenal Fat Thickness (PRAT) may exhibit expansion, remodeling and inflammation that can negatively affect renal outcomes in LKDs.

Researchers will compare PRAT morphology and inflammation in LKDs with low and high PRAT thickness.

We will also correlate PRAT thickness with renal outcomes including vascular remodeling, at the time of donation and worsening hypertension and inadequately increased compensatory GFR of the LKD at 4-6 months post-donation.

Participants will be separated into one of two groups depending on their PRAT measurement and asked to give samples of their blood, perinephric fat, and urine as research samples. Clinically we will abstract data up to 12 months prior and 6 months after their nephrectomy that includes laboratory findings, CT measurements, vitals, exam data, demographics, medical history and current medications.

6.1 Screening Visit Patients who have had their donor nephrectomy scheduled will be approached for enrollment. Potential participants must preliminarily meet all inclusion and no exclusion criteria to be approached by a study team member about study participation. If there is 10% (or greater) weight loss between the clinical donor evaluation visit and the potential screening visit the individual will not be approached for enrollment.

If all required inclusion and no exclusion criterion are met, the study team will present the consent form to the potential participant.

After the consent form has been signed, the following study procedures will be performed at the screening visit:

• The following information will be collected study team member will review the participant's demographic information, m The following information will be recorded from the participant's from their electronic medical record

  • Participant's demographic information
  • Medical history and current medications and, if needed, ask the participant clarifying questions
  • Pregnancy test results (if applicable)
  • Current medications
  • Most recent weight
  • Height
  • BMI
  • Clinical Donor Evaluation
  • PRAT Measurement

• The following lab results will also be collected from the medical record

  • Creatinine with eGFR
  • Comprehensive Metabolic Panel Glucose
  • Fasting Lipid Profile
  • HbA1c
  • 24-hour Urine for Albumin Excretion

• An 18-hour ABPM may be completed with subject consent at either the Screening Visit or Visit 1 if (if it has not been obtained clinically 6 months prior to the scheduled donor nephrectomy) or there has been a clinically significant blood pressure medication changes. A sphygmomanometry measurement will be collected at each visit unless the 18-hour ABPM is performed.

Serious adverse events will also be recorded and addressed as applicable at every study visit after the participant signs consent. All adverse events will be recorded from Visit 2 until the subject completes or is withdrawn from the study.

In applicable situations (i.e., the subject does not need to be seen in person to complete all study procedures) the screening visit can be completed remotely.

After this information has been collected, participants will be categorized into 1 of the 2 groups based upon their PRAT measurement and BMI. If the PRAT thickness or the BMI does not meet study criterion, the participant will be considered a screen failure.

6.2 Visit 1

During this visit, the following study procedures will also occur:

• The study team will record the following information from the medical record:

  • Changes in the participant's medical history or medications.
  • Participant's current weight and height.
  • Participant's BMI

• 10 mL of blood and 50mL urine will also be collected for research purposes.

• An optional 18-hour ABPM may be completed if the subject has consented to this procedure and it was not collected during the screening visit. If a subject declines the 18-hour ABPM a sphygmomanometry measurement will be collected.

6.3 Visit 2

Visit 2 will occur the day of the living kidney donor's nephrectomy. During this visit, the study team will perform the following:

• Record the following information from the participant's medical record:

  • changes to the medical history or medications.
  • The participant's current weight and height
  • Participant's BMI
  • Information on the nephrectomy.
  • Hemoglobin
  • 24-hour ABPM

• During the nephrectomy, the study team will collect a 5-10g fat sample for research analysis.

6.5 Visit 3

This visit will take place approximately 6 months after the donor nephrectomy. During this visit, the study team will:

• Record the following information from the EMR:

  • Any changes to the participant's medical history or medications.
  • The participant's current weight and, height.
  • Current BMI
  • The participant's blood pressure, via sphygmomanometry.
  • Creatinine with eGFR
  • Fasting Lipid Profile
  • Glucose

• An 18-hour APBM will be completed with participant consent and if it was not completed as a part of clinical care. If a subject declines the 18-hour ABPM a 6h AMBP monitoring performed clinically will be collected

• 10 mL of blood and 50 mL of urine will be collected for research purposes.

Inclusion Criteria:

• Participants in this study will be restricted to living kidney transplant donors (LKDs). .

Exclusion Criteria:

• Those who do not meet Mayo Clinic Rochester's clinical criterion for donor nephrectomy.
• >10% weight change between the donor evaluation and donor nephrectomy
• Individuals who are pregnant or are planning to become pregnant
• Inability to comply with study procedures or any condition that, in the opinion of the investigator, could increase the patient's risk by participating in the study or confound the outcome of the study.

Living kidney donors scheduled for nephrectomy ages 18 - 80