An interventional study of Low-oxalate diet and High-oxalate diet in Kidney Stone, Kidney Calculi and Urolithiasis, sponsored by University of Alabama at Birmingham. Recruiting at 2 sites in United States. Open to participants aged 18 Years to 80 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-13.
Sponsored by University of Alabama at Birmingham · Not applicable, Interventional, and Basic science
The goal of this clinical trial study is to test if patients with idiopathic calcium oxalate kidney stones have an increased absorption of dietary oxalate, which would lead to increased urinary excretion of oxalate.
The study will recruit adult patients with a history of calcium oxalate kidney stones and healthy volunteers without kidney stones.
Participants will
In this study the investigators propose to measure the net gastrointestinal absorption of oxalate both by food-bound oxalate, using low- (\<60 mg/day) and high- (250-300 mg/day) oxalate diets (600-800 mg daily calcium in both), and by the soluble 13C2-oxalate oral test in both Calcium Oxalate Kidney Stone patients and matched controls.
Phase 1. Screening and low-oxalate diet 24-hr urinary excretions. Between the University of Alabama at Birmingham (UAB) and the University of Texas Southwestern Medical Center (UTSW), the study will enroll 40 subjects with idiopathic Calcium Oxalate Kidney Stone (20 Males/20 Females) and 40 non-kidney stone forming controls (20 Males/20 Females). Participants in the two groups will be matched for age (within 10 yrs) and gender. Screening will include blood complete metabolic profile and two 24-hr urine specimens collected at home on self-choice diets and anthropometric measurements.
Participants will then ingest the controlled low-oxalate (\<60 mg/d) diet for 5 consecutive days and collect two 24-hr urines after 2 days of dietary equilibration.
Phase 2. 13C2-Oxalate gut absorption tests. On Day 5, participants will arrive after an overnight fast in the research unit to undergo the 13C2-oxalate absorption test. After a 1-hour baseline urine collection, they will ingest an oral load containing 100 mg 13C2-oxalate and 1 g sucralose, dissolved in bottled water. For the next 9 hrs, blood and urine will be collected hourly, and breath as more time points. They will remain on the fixed diet for 24 hrs with a breakfast 2 hours after the load, lunch 6 hrs post-load, and dinner at home 12 hrs post-load. They will collect the remainder of their 24-hr urine at home and the totality of the stool eliminated during the first 24 hrs after the load using kits provided.
Phase 3. High-oxalate diet 24-hr urinary excretions. After a minimum of 1 week wash-out period, during which participants will eat freely, participants will consume the high oxalate (250-300 mg/day) diet for the next 4 days. Two 24-hr urine specimens will be collected after 2 days of equilibration and a fasting blood draw on the morning of Day 5.
.
509 studies on the registry are indexed under Kidney Calculi; 146 are open to participants now.
This study's planned enrollment of 80 is close to the median of 86 across 391 interventional studies indexed under Kidney Calculi.
Browse Kidney Calculi studies →University of Alabama at Birmingham is the lead sponsor of 1,421 studies on the registry; 277 are open to participants now.
Of its 164 completed or terminated interventional studies of FDA-regulated products, 130 (79%) have results posted.
Counted across the registry records on this site, refreshed daily.
The criteria were revised on the registry on Oct 13, 2026. See what changed
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Low and High oxalate fixed diets. Soluble oxalate absorption test.
Dietary Supplement: Low-oxalate diet · Dietary Supplement: High-oxalate diet · Other: soluble oxalate gut absorption test
Low and High oxalate fixed diets. Soluble oxalate absorption test.
Dietary Supplement: Low-oxalate diet · Dietary Supplement: High-oxalate diet · Other: soluble oxalate gut absorption test
4 days of fixed eucaloric diet with low oxalate (\<60 mg/day), normal calcium content (600-1000 mg/day)
4 days of fixed eucaloric diet with moderately high oxalate (250-300 mg/day), normal calcium content (600-1000 mg/day)
Oral ingestion of 13C2-oxalate and sucralose.
Net Gastrointestinal absorption of food-bound oxalate
difference between 24-hour urinary oxalate excretion on the high oxalate diet and the low oxalate diet, normalized to the difference in dietary oxalate composition of the two diets (%)
Time frame: 4 day
Absorption of soluble 13C2-oxalate
Proportion of 13C2-oxalate recovered in urine to the amount orally ingested (%)
Time frame: 1 day
Estimated endogenous oxalate synthesis (oxalate mg/day)
24-hour urinary oxalate excretion on the low oxalate diet (mg/day)
Time frame: 2 days
Plan to share: No
No publications or documents are linked to this record.
Started Apr 2024 (actual). Primary completion is estimated for Dec 2030, 80 months after the start.
Of 183 non-industry interventional studies with no phase under Kidney Calculi, half reached primary completion within 31 months of starting (the median), counting those still running; a quarter within 13 and three quarters within 54. This study's planned 80 months is above that.
Counting every sponsor, half of 199 studies reached it within 26 months; a quarter within 12 and three quarters within 51.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
University of Alabama at Birmingham →