An interventional study of Low-oxalate diet and glycolate dosing and Oral glycolate dosing in Kidney Stones, 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 2026-08-27.
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 production of oxalate by the body, 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
ingest fixed diets containing low amounts of oxalate for 5 days ingest a soluble form of glycolate and vitamin C collect urine, blood, stool during the dietary and oral dosing portions of the study and also collect breath sample during the oral glycolate test
In this study the investigators propose to measure the production of oxalate by the body (endogenous oxalate synthesis), after equilibration on a low oxalate diet (\<60 mg oxalate/day, 600-800 mg calcium/day) and estimate the importance of vitamin C and glycolate metabolism to oxalate production in both Calcium Oxalate Kidney Stone patients and matched controls by oral dosings of those two substances.
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-hour urine specimens collected at home on self-choice diets and anthropometric measurements.
Participants will then ingest the controlled low-oxalate (\<60 mg/day) diet for 5 consecutive days and collect two 24-hour urines after 2 days of dietary equilibration.
Phase 2. Oxalate production and 13C-glycolate dosing tests. On Day 5, participants will arrive after an overnight fast in the research unit to undergo the oral 13C-glycolate dosing test. After a 1-hour baseline urine collection, they will ingest an oral load containing 0.5 mg/kg body weight of 13C-glycolate, dissolved in bottled water. For the next 7 hours, blood and urine will be collected hourly, and breath as more time points. They will remain on the fixed diet for 24 hours with a meal 7 hours post-load, and dinner at home 12 hours post-load. They will collect the remainder of their 24-hour urine at home.
Phase 3. Oxalate production and 13C-ascorbic acid dosing tests. After 1 day of equilibration on the same low-oxalate diet, participants will arrive after an overnight fast in the research unit to provid eone blood and one urine sample and then ingest an oral dose of 13C-ascorbic acid (0.75 mg/kg), return home and continue to ingest the low-oxalate diet. The next morning, participants will arrive after an overnight fast in the research unit. For the next 7 hours, blood and urine will be collected hourly. They will remain on the fixed diet for 24 hours with a meal at the end of the visit.
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.
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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 oxalate fixed diets. oral glycolate and ascorbic acid administration
Dietary Supplement: Low-oxalate diet and glycolate dosing · Dietary Supplement: Oral glycolate dosing · Dietary Supplement: Oral 13C- ascorbic acid dosing
Low oxalate fixed diets. oral glycolate and ascorbic acid administration
Dietary Supplement: Low-oxalate diet and glycolate dosing · Dietary Supplement: Oral glycolate dosing · Dietary Supplement: Oral 13C- ascorbic acid dosing
Low-oxalate diet 4 days of fixed eucaloric diet with low oxalate (\<60 mg/day), normal calcium content (600-1000 mg/day)
Oral 13C-glycolate dosing (0.5 mg/kg)
Oral 13C- ascorbic acid dosing (0.75 mg/kg)
Estimated endogenous oxalate synthesis (oxalate mg/day)
Basal rate of endogenous oxalate synthesis estimated by repeat fasted hourly urine collections (mg/day)
Time frame: 1 day
24-hour urinary oxalate excretion on low oxalate diet
mean 24-hour urinary oxalate excretion on the low oxalate diet (mg/day)
Time frame: 2 days
contribution of ascorbic acid breakdown to urinary oxalate excretion
contribution of ascorbic acid breakdown to oxalate synthesis (%)
Time frame: 2 days
Contribution of glycolate metabolism to urinary oxalate
Proportion of 13C-glycolate orally dosed that is metabolized to urinary 13C-oxalate in the fasted stated (%)
Time frame: 1 day
Plan to share: No
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Studies of the drug tested here: Carbon-13
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