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.