Fecal Microbiota Transplantation in Kidney Stone Patients

Inclusion Criteria: * Age 18 years or older and younger than 70 years. * Recent urinary stone disease with at least 50% calcium-oxalate composition confirmed by stone analysis. * 24-hour urinary calcium \>225 mg/day or urinary oxalate \>40 mg/day. * Able to provide informed consent. * Willing to complete safety follow-up, study visits, 24-hour urine collections, and serial stool collections. * Not actively participating in another interventional urinary stone disease trial. * eGFR \>=60. Exclusion Criteria: * Three or more NIH-defined metabolic syndrome features. * Any autoimmune disease or inflammatory bowel disease. * Major gastrointestinal surgery within 3 months, excluding appendectomy or cholecystectomy; history of total colectomy or bariatric surgery. * Primary or secondary hyperparathyroidism or PTH outside 15-65 pg/mL. * Pancreatic enzyme replacement, ongoing dialysis, or eGFR \<60. * Chemotherapy in the prior year or concurrent intensive cancer therapy. * Antibiotics within 3 months of study entry, continued antibiotic need, or anticipated antibiotic use in the next 4 weeks. * Unable to complete required washout from potassium citrate, thiazides, or proton pump inhibitors. * Pregnant, breastfeeding, or planning pregnancy during the study. * Unable or unwilling to swallow capsules, including CTCAE grade \>=2 dysphagia. * Active gastrointestinal infection, toxic megacolon, or small bowel ileus. * Life expectancy \<6 months. * Prior FMT or microbiome-based product outside this study. * Severe anaphylactic or anaphylactoid food allergy. * Solid organ transplant recipient. * Any condition jeopardizing safety or rights, preventing completion, or confounding results. * Urinary oxalate \>=80 mg/day.