PROJECT SUMMARY Young adults 18-40 years of age with cerebral palsy (CP) have unmet healthcare needs and heightened susceptibility for kidney disease, which may result in greater risk for premature morbidity and mortality; however, little is known about kidney function for individuals with CP. This is due to misinterpretation of clinical measures of kidney function that are not appropriate for CP, leading to inaccurate assessment of kidney function. Interventions at earlier stages of kidney dysfunction can be highly effective at mitigating long-term risk of kidney disease; however, intervention efforts are hindered without accurate assessments of glomerular filtration rate (GFR), the clinical gold-standard measure of kidney function, in patients with CP. No studies have measured GFR (mGFR) for CP. The feasibility of obtaining mGFR in adults with CP is unknown, as is the accuracy of estimating GFR (eGFR) using traditional equations through non-invasive methods. There may be specific barriers in mGFR testing for adults with CP. Therefore, identifying clinical feasibility and reasonable accommodations to accurately assess mGFR is a vital first step. The long-term goal is to understand, prevent, and treat kidney dysfunction to improve healthful aging for individuals with CP. The objective of this study is to lay the foundation for future research and clinical intervention by determining the clinical feasibility of obtaining mGFR using the widely adopted clinical test, 125I-Iothalamate, and the 99mTc-DTPA test, which is a less- involved clinical protocol, for young adults 18-40 years old with CP. Specifically, the primary Aim of this study will measure the proportion of those consented to those approached, proportion of those completing testing procedures to those consented, acceptability of testing using validated measures, and exit interviews that probe barriers and facilitators to enrollment and testing challenges for both the participants with CP and the experienced technicians obtaining mGFR. The exit interviews will allow us to identify and develop reasonable accommodations to enhance recruitment and completion of testing for future research studies and to inform clinical practice. If both clinical protocols prove reliable mGFR measures as determined by routine clinical standards, we will explore: (1) the agreement between tests, which will provide evidence of which test can be used for research and clinic; and (2) the degree of discrepancy between mGFR and eGFR by severity of CP. This information will initiate needed work in providing a clinically-friendly CP correction factor or a CP-specific equation for eGFR to improve clinical monitoring of kidney function for this vulnerable population. The research is innovative because it will challenge the current status quo that kidney function is normal for CP, which is due to misinterpretation of kidney function from routinely used clinical measures that are not appropriate for CP rather than true ki...