Actively Recruiting
Gastrointestinal Oxalate Absorption in Calcium Oxalate Stone Disease
Led by University of Alabama at Birmingham · Updated on 2026-05-28
80
Participants Needed
2
Research Sites
52 weeks
Total Duration
On this page
Sponsors
U
University of Alabama at Birmingham
Lead Sponsor
U
University of Texas Southwestern Medical Center
Collaborating Sponsor
AI-Summary
What this Trial Is About
Researchers are evaluating whether patients with idiopathic calcium oxalate kidney stones absorb more dietary oxalate, which may cause increased oxalate in their urine. The study includes adults with a history of calcium oxalate kidney stones and healthy volunteers without stones. The aim is to understand oxalate absorption using diets with different oxalate levels and a soluble oxalate test. Participants will follow fixed diets: a low-oxalate diet (under 60 mg/day) and a moderately high-oxalate diet (250-300 mg/day), each with normal calcium levels. They will complete a soluble oxalate gut absorption test by ingesting labeled oxalate and sucralose. The study involves three phases: screening and low-oxalate diet with urine collection; a 13C2-oxalate absorption test with blood, urine, breath, and stool samples; and a high-oxalate diet phase with urine and blood testing. During the study, participants will provide multiple samples including urine, blood, stool, and breath to measure oxalate absorption and synthesis. They will keep fixed diets for several days and collect urine at home. Researchers will monitor urinary oxalate excretion and absorption of soluble oxalate. The total participation includes diet periods, tests, and sample collections lasting over several weeks, with safety monitoring and wash-out periods between diets.
CONDITIONS
Brief Title
Gut Oxalate Absorption in Calcium Oxalate Stone Disease
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Age 18 to 70 years
- Body Mass Index greater than 18.5 kg/m2
- Normal fasting serum electrolytes on metabolic profile
- Willing to follow fixed diets
- Willing to stop vitamins, calcium supplements, herbal supplements, probiotics, and nutritional aids for 2 weeks before and during the study
- For stone formers: first time or recurrent calcium oxalate stone formers with most recent stone composition at least 50% calcium oxalate and uric acid less than 20% if available
You will not qualify if you...
- Chronic Kidney Disease stage 4 or 5
- Primary or secondary hyperoxaluria
- Liver, bowel, endocrine, or renal diseases other than idiopathic calcium oxalate stones, including cystic fibrosis, celiac disease, cystinuria, nephrotic syndrome, sarcoidosis, renal tubular acidosis, primary hyperparathyroidism, neurogenic bladder, urinary diversion, chronic diarrhea, bariatric surgery, inflammatory bowel disease
- Pregnancy or breastfeeding
- Dietary restrictions incompatible with study foods or food allergies/intolerances
- Active cancer or cancer treatment within 12 months prior to screening
- Use of immunosuppressive medications
- Uncontrolled hypertension or diabetes
- Type 1 diabetes
- Chronic use of NSAIDs
AI-Screening
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Your Study Journey
Duration - 2 to 4 weeks
Participants are screened for eligibility to participate in the trial.
Blood tests and 24-hour urine collections at home are completed during screening.
Duration - 5 days
Participants consume a fixed low-oxalate diet for 5 consecutive days while collecting 24-hour urine samples after 2 days of diet equilibration.
Participants collect two 24-hour urine samples at home during this period.
Duration - 1 day
Participants undergo a 13C2-oxalate oral absorption test involving fasting, oral ingestion of labeled oxalate, and collection of blood, urine, and breath samples over 9 hours, remaining on the fixed diet.
1 in-person visit for the absorption test and hourly sample collections over 9 hours, plus home collection of 24-hour urine and stool samples.
Duration - At least 1 week
Participants eat freely for at least 1 week before starting the next diet phase.
No study visits during this period.
Duration - 5 days
Participants consume a fixed high-oxalate diet for 4 days while collecting 24-hour urine samples after 2 days of diet equilibration, with a fasting blood draw on the morning of Day 5.
Participants collect two 24-hour urine samples at home and attend 1 fasting blood draw visit.
Trial Site Locations
Total: 2 locations
1
University of Alabama at Birmingham
Birmingham, Alabama, United States, 35294
Actively Recruiting
2
UTSW
Dallas, Texas, United States, 75390
Active, Not Recruiting
Research Team
S
Sonia Fargue, PhD
How is the study designed?
Study Type
INTERVENTIONAL
Masking
NONE
Allocation
NON_RANDOMIZED
Model
PARALLEL
Primary Purpose
BASIC_SCIENCE
Number of Arms
2
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