A Pilot Study of Oxalate Absorption in Secondary Hyperoxaluria

Study Overview
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Brief Summary
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Identify individuals with greater absorption of oxalate based on increase in urinary oxalate excretion in response to a controlled oxalate-rich test meal.

Detailed Description
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This was a prospective 4-day study of oxalate absorption in subjects with secondary hyperoxaluria. Subjects visited the research center three times for outpatient visits (Screening, Test Day 3, Day 4). Subjects were instructed to follow a low-oxalate diet, consuming only study-specified food choices that had low or no oxalate and controlled calcium content Days 1 through 4 (Baseline Period through the Day 4 clinic visit) and, on Test Day 3, consumed an oxalate-rich test meal. Subjects performed three 24-hour urine collections during Screening, Baseline Day 2, and Test Day 3. Test Day 3 included the oxalate-rich test meal and the subject collected a 24-hour urine separated into 4 urine collection intervals. (Pre-test meal, post-test meal to 4 hours, 4-6 hours post test meal and remaining time to complete 24 hours).

Official Title
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A Pilot Study of Oxalate Absorption in Secondary Hyperoxaluria

Conditions
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Nephrolithiasis, Secondary Hyperoxaluria, Hyperoxaluria, Kidney Stones

Intervention / Treatment
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* Other: Test Meal


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Males or non-pregnant and non-lactating females History of hyperoxaluria secondary to a known underlying enteric disease (e.g., Crohn's disease, bariatric surgery, and others) or without a known underlying cause (idiopathic), and kidney stones. Urinary oxalate ≥ 40 mg of oxalate/24 hr at screening. If taking drugs for the prevention of stone disease, including pyridoxine, thiazides (chlorthalidone, hydrochlorothiazide, and indapamide), citrate supplements, and allopurinol, there must have been no changes in these medications for at least one month prior to screening and no changes are anticipated for the duration of the study. Able to understand and provide written informed consent. Exclusion Criteria: Under or over-collection on screening 24-hour urine collection (mg creatinine/kg body weight outside of gender-specific range). Estimated glomerular filtration rate (eGFR) <40 mL/minute/1.73 m^2 or acute renal failure. Primary hyperoxaluria. Allergy, intolerance, or any other factors limiting ability to consume the study foods or adhere to the study meal schedule. Positive pregnancy test during Screening. Clinically significant findings (including acute renal colic), an ongoing clinically significant illness requiring changes in management, or any planned medical/surgical procedure during the study. Malignancy undergoing active therapy; patients in remission on chronic suppressive or maintenance therapies are not excluded. Investigational compound within 30 days prior to screening. Investigator determined that the subject would not be able to adhere or to complete the study procedures , or could not discontinue Vitamin C supplements, calcium supplements, or other medications that could interfere with oxalate absorption and/or excretion.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Test Meal<br>controlled oxalate-rich test meal | Other: Test Meal<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percent of Oxalate Absorption Normalized by Baseline Urinary Oxalate Excretion Over a 24 Hour Test Period | Percent of oxalate absorption normalized by baseline was calculated by 100*[UOx/test - UOx/baseline]/Ox intake from the test meal. | 24 hours during baseline and test day following oxalate-rich meal | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percent of Oxalate Absorption By Test Interval | Percent of Oxalate absorption by test interval was calculated as the urinary oxalate excretions (mg) during the test interval divided by the amount of oxalate in the test meal. | 0-4 hours post test meal, 0-6 hours post test meal, 0-24 hours post test meal | 
| Percent Change From Baseline for Urinary Oxalate to Creatinine Ratio by Test Interval | Urinary oxalate (UOx) excretion was normalized to units of mg/g creatinine by dividing the UOx in mg by the creatinine value in g from the same collection. Percent change from baseline for UOx/Cr from Baseline was calculated by 100 * [UOx/Cr for the test interval - UOx/Cr at Baseline] / UOx/Cr at Baseline. | 24 hours during baseline, 0 to 4 hours post test meal, 0-6 hours post test meal, 6-24 hours post test meal, 0-24 hours post test meal | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Urine Oxalate, Nephrolithiasis, Kidney Stones, Hyperoxaluria, Enteric Hyperoxaluria, urological Diseases, Kidney Diseases, Dietary Oxalate, Idiopathic Hyperoxaluria, Oxalate Absorption