Uric Acid Nephrolithiasis Clinical Trial
Official title:
Renal Uptake of Fatty Acids (FFA) in Patients With Idiopathic Uric Acid Nephrolithiasis (IUAN)
The investigators will test the hypothesis that renal uptake of free (i.e. non-esterified)
fatty acids (FFa) is increased in iuan. To accomplish this goal the investigators will
measure renal FFa uptake FFa uptake in vivo in patients with iuan and matched non-stone
forming subjects via single-photon emission computed tomography (SPeCT)/CT imaging.
The definitive proof of the hypothesis rests on whether increased renal FFa uptake is
demonstrable in humans with iuan.
This is a cross-sectional study of patients with iuan and matched non-stone formers to test
the hypothesis that renal FFa uptake is increased in iuan, using noninvasive 123i-labeled
[MiCRo-SYMBoL]-methyl-p-iodo-phenyl-pentadecanoic acid(123i-BMiPP) SPeCT/CT imaging, an
established FFa analog approved for human studies.
Participants will be placed on an instructed controlled metabolic diet (30% fat, 15% protein,
55% carbohydrate, 300 mg cholesterol per day, 400 mg calcium, 800mg phosphorus, 100 meq
sodium, with low acid ash content, and 3000 cc distilled water) for 5 days to exclude dietary
confounders (3 days as outpatient and the final 2 days as inpatient). On days 4 and 5, two
fasting blood samples will be collected for the measurement of CMP, insulin, FFa and two 24-h
urine samples will be collected under mineral oil to be analyzed for total volume, pH, Cr,
na, K, Ca, Mg, Cl, P, uric acid, nH4+, titratable acidity (Ta), sulfate, HCo3- and citrate.
The morning of day 6, patients will undergo dual 123i-BMiPP and 99mTc-MaG3 (99mTc
mercaptoacetyltriglycine mertiatide) SPeCT/CT imaging after 12 hrs of fasting. 99mTc-MaG3
(8-10mCi) will be injected intravenously for the flow phase of a standard renal scan which
includes dynamic imaging for 2 minutes. an additional 1 minute image will be acquired (the
2-3 minute image on a standard renal scan). acquisition will then stop. immediately afterward
123i-BMiPP (4-5mCi) will be injected intravenously for a 1hour uptake period. after the 1
hour uptake dual isotope (Tc-99m and i-123) SPeCT/CT images of the kidney will be acquired on
a clinical Siemens Symbia dual head SPeCT/CT system. The 99mTc-MaG3 flow image data will be
used to measure renal plasma flow,12 using the Ge Xeleris renal analysis software package
already installed on the clinical SPeCT/CT system. The 123i-BMiPP, a gamma emitter with a
half-life of 13.13 hours, is to measure renal 123i-BMiPP (FFa) uptake 13 123i-BMiPP uptake
will be corrected for effective renal plasma flow (mL/min) measured with 99mTc-MaG3, using
the Ge Xeleris renal analysis software package.
Expected findings: If the hypothesis is correct, the investigators expect increased FFa
uptake as measured by 123i-BMiPP SPeCT/CT corrected for renal effective plasma flow in the
kidney cortex of iuan patients vs. matched controls.
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