Long Term Impact of Pediatric Acute Renal Injury in Severe Sepsis

Inclusion Criteria: For non-acute kidney injury (AKI) sepsis patients: 1. Hospitalization with a diagnosis of sepsis from 1998-2014 2. Failure to meet pediatric Risk Injury Failure Loss End stage (pRIFLE) criteria for AKI during incident admission. 3. Participation in cognitive survey study with completion of survey For sepsis related AKI patients: 1. Hospitalization with a diagnosis of sepsis from 1998-2014 2. Need for renal replacement therapy (RRT) 3. Severe AKI as defined by the pRIFLE criteria (estimated CrCl (eCrCl) decrease by 50%, eCrCl \<60 ml/min/1.73 m2, or a urine output \<0.5 ml/kg/h for 24 h or anuric for 12 h) during the sepsis admission 4. Participation in cognitive survey study with completion of survey For healthy control patients: 1\. Identified from the neurology service who are scheduled for MRI with gadolinium as part of their clinical care Exclusion Criteria: For all patients: 1. Known pre-existing chronic kidney disease (CKD) as defined by history of kidney transplant or long-term dialysis 2. Age greater than 18 years at the time of sepsis admission 3. AKI from primary kidney disease including acute glomerulonephritis and obstructive uropathy 4. Pregnancy at the time of enrollment 5. Age younger than 5, between the ages of 12 to 17, or over the age of 24 at the time of enrollment. For healthy control patients: 1. Chronic kidney injury (CKD) 2. History of acute kidney injury 3. History of any chronic illnesses (e.g. cancer)