Chronic Kidney Disease in Children Prospective Cohort Study (CKiD)

Inclusion Criteria: * Age between 1 and 16 years (before 17th birthday) for Cohorts 1 and 2; age between 6 months and 16 years (before 17th birthday) for Cohort 3; age between 16 to 22 years (before 23rd birthday) for Cohort 4 and regularly seen by pediatric nephrologist prior to enrollment * Estimated (based on SCr) Schwartz GFR between 30 and 90 ml/min\|1.73m2 for Cohort 1 OR an estimated GFR between 45 and 90 ml/min\|1.73m2 based on the updated Schwartz formula for Cohort 2; an estimated GFR ≤60 based on the CKiD Under 25 estimating equation (U25eGFR) OR KRT experience (dialysis or transplant) for Cohort 4 * Willingness and ability to provide informed consent and assent * For Cohort 3, children with non-glomerular diagnosis and duration of kidney disease less than 5 years will be enrolled. Exclusion Criteria: * Solid organ (other than kidney), bone marrow or stem cell transplantation * Cancer diagnosis and receiving treatment or within 12 months post completion of treatment * HIV diagnosis and receiving treatment or within 12 months post completion of treatment * Current pregnancy or pregnancy within past twelve months * Inability to complete major data collection procedures * Not fluent in English or Spanish * Plans to move out of area of any participating CKiD site (families can be transferred to another CKiD site if the family moves) * Existing moderate to severe congenital structural heart disease * Genetic syndromes involving the central nervous system (e.g., Downs syndrome) * History of severe to profound intellectual disability (i.e., Intelligence Quotient (IQ)\<40, significant impairment in adaptive function and/or inability to independently execute self-care skills) * For cohort 3, children who are expected to receive renal replacement therapy within 6 months of date of enrollment will not be recruited