RecruitingClinical trialGut Kidney Axis in Enteric Hyperoxaluria40 subjects with a confirmed diagnosis of IBD or \>6 months post-RYGB with a diagnosed USD event or kidney stone on imaging within the past three years and 40 healthy controls will be administered a high oxalate diet on Days 0-3 and Days 21-24 with a washout period on Days 4-7 and will be administered 250mg sodium oxalate on Days 8-20, via prepared spinach, from Weil Cornell Medicine's Clinical and Translational Science Center. Subjects will partake in four stool collections, four 24-h urine collections, two blood collections, and four sets of colonic permeability testing.