Methodological Variations in 24-Hour Urine Collection for Nephrolithiasis: A Systematic Review of Reporting Practices and Clinical Implications.

Oral citrate supplements have been shown to decrease kidney stone recurrence rates in both laboratory and clinical studies. The taste of the citrate supplements, however, is poor, and long-term compliance is low. Our objective was to determine if Splenda(®) added to potassium citrate (KCit) improves palatability without changing 24-hour urine parameters. 12 subjects were randomly assigned to receive either KCit alone for 3 days or KCit + Splenda in a double-blind trial. The 24-hour urine collections were performed before and after 3 days of therapy. After 1 week, the two groups switched treatments. After each treatment, a visual analog taste scale was completed to gauge the taste and palatability. The 24-hour urine parameters of kidney stone risk factors were compared between groups. The primary end points were to determine whether Splenda improved palatability of citrate supplementation and whether it altered 24-hour urine parameters. Taste was judged to be 2.5 ± 0.9 points better in the Splenda + KCit compared with KCit alone (P=0.02). The 24-hour Cit, K, and pH were significantly higher in the KCit and KCit + Splenda groups compared with baseline, but not significantly different from each other. Splenda significantly improves the palatability of KCit therapy and does not alter the beneficial effects of KCit on 24-hour urine Cit, K, or pH. The addition of Splenda altered the average taste score from one that might prohibit compliance to one that would not.

Key PointsIn a cross-sectional study, sodium-glucose cotransporter 2 inhibitors were associated with a significant increase in urine volume and urine citrate.Glucagon-like peptide-1 receptor agonists were not associated with any significant changes in 24-hour urine parameters that affect stone formation.BackgroundEmerging data suggest sodium-glucose cotransporter-2 inhibitors (SGLT2is) and glucagon-like peptide-1 receptor agonists (GLP-1RAs) may lower stone risk.MethodsWe characterized 24-hour urine parameters among patients with kidney stone disease receiving these agents using Medicare claims from beneficiaries with urine collections processed by a central laboratory between January 2010 and December 2019. We identified a cross-sectional cohort with diabetes and a prescription fill for SGLT2is or GLP-1RAs within the 6 months preceding their urine collection and matched controls. We additionally identified a subset of patients who performed two collections and had a prescription fill for SGLT2is or GLP-1RAs before the second collection, but not the first. We compared across 24-hour urinary parameters in both cohorts and adjusted for multiple comparisons.ResultsThe cross-sectional cohort included 124 patients with a prescription fill for SGLT2is (and 620 matched controls) and 349 patients with a prescription fill for GLP-1RAs (and 349 matched controls). Compared with controls, patients on SGLT2is had a higher mean urine citrate (838 versus 636 mg; P < 0.01) and volume (2.4 versus 2.0 L; P < 0.01) with improved calcium phosphate supersaturation (P < 0.01). Lower urine pH and higher sulfate and uric acid were observed in the SGLT2i group (P < 0.01 for each). There were no significant differences in urine parameters with GLP-1RA. In the longitudinal analyses of SGLT2is (59 patients) and GLP-1RAs (154 patients), there were no significant differences in urinary parameters.ConclusionsSGLT2is were associated with higher urine volume and citrate in a cross-sectional cohort. GLP-1RAs were not associated with changes that would reduce stone risk.

To evaluate 24-hour urine composition prior to and after complete stone removal in nephrolithiasis patients to determine potential relationship between kidney stones and patient metabolic status. A prospective observational study was performed with patient enrollment from March 2019 to August 2020. 24-hour urine samples were collected prior to stone removal and 4 weeks after double-J stent removal, and examined the following urinary parameters: volume, creatinine, sodium, calcium, uric acid, citrate, oxalate, potassium, phosphorous, magnesium, and pH value. For each parameter, pairwise t test was performed to compare samples prior to and after stone removal. The number of cases that changed from normal to abnormal or vice versa was also evaluated for each parameter. The study was registered at http://clinicaltrials.gov/ (NCT03846011). A total of 109 patients completed 24-hour urine collections prior to and after stone removal. The urinary calcium and phosphate levels increased significantly after stone removal, showing a mean difference of 0.55 mmol (P=0.015) and 2.35 mmol (P=0.001) respectively. None of the other urinary parameters demonstrated a statistically significant difference when means were compared. The percentage differences for all urinary parameters ranged from 5.4% to 14.1%. The percentages of patients that presented clinically significant changes in urinary parameter values from normal to abnormal or vice versa ranged from 4.6% to 20.1%. Ideally, evaluation of 24-hour urine compositions should be undertaken after total stone removal, especially for patients with calcium stones. For patients who cannot achieve total stone removal, 24-hour urine samples should be thoroughly interpreted as urinary calcium and phosphate levels might be depleted in the presence of urinary stones.

BackgroundThe 24-hour uric acid excretion measurement is important in assessing disease status and helping to select the appropriate uric acid-lowering agent for patients with gout, however, it is inconvenient. The authors investigated the efficacy of the random urine uric acid-to-creatinine (UA/CR) ratio to screen the patients who under-secreted 24-hour urine uric acid.MethodsThis was a retrospective cross-sectional study. Ninety patients with gout, without undergoing uric acid-lowering treatment were enrolled. Twenty-four-hour urine and random urine samples were obtained on the same day. Six hundred mg of uric acid in the 24-hour urine sample was used as a standard for distinguishing between over and under-excretion groups.ResultsThe random urinary UA/CR ratio showed positive correlation with 24-hour urine uric acid excretion (γ = 0.398, P < 0.001). All the patients with the random UA/CR less than 0.2 excreted less than 600 mg uric acid in 24-hour urine collection. When the random urine UA/CR ratio < 0.2 was regarded as a positive result, the positive predictive value, negative predictive value, sensitivity, and specificity in the uric acid under-excretion were 100% (8 of 8), 64.6% (53 of 82), 21.6% (8 of 37), and 100% (53 of 53), respectively.ConclusionThere is a moderate positive correlation between the random urinary UA/CR ratio and 24-hour urine uric acid excretion, so that UA/CR ratio may not be a good predictor of 24-hour urine uric acid excretion. However, the random urine UA/CR ratio 0.2 can be a useful predictor to screen the gouty patients who need to be treated with uricosuric drugs.

Patient adherence limits the effectiveness of preventive pharmacologic therapy (PPT) for urinary stone disease (USD), highlighting the need for accurate adherence monitoring. We assessed associations between potassium citrate adherence measures, changes in 24-hour urine parameters, and the risk of recurrent stone events. In this retrospective cohort study, we identified adults enrolled in Medicare with USD, a baseline 24-hour urine collection (2010-2019), hypocitraturia or low urine pH, a prescription for potassium citrate monotherapy, and a follow-up urine collection. We defined two adherence measures: (1) percentage of days covered (PDC) using pharmacy claims and (2) change in urinary potassium between baseline and follow-up divided by medication dose (ΔK/dose). We assessed the association of these measures with changes in urinary citrate and pH using analysis of covariance, and the association between adherence and recurrent stone events using Cox models. Among 793 patients meeting study criteria, 504 (63.6%) were adherent based on pharmacy claims (PDC≥80%) and 389 (49.1%) based on ΔK/dose≥0.5. Compared to PDC≥80%, ΔK/dose≥0.5 had a stronger association with change in urinary citrate (p<0.001) and pH (p<0.001). Compared to PDC≥80%, patients with PDC<80% had a higher risk of recurrent stone events (hazard ratio [HR] 1.431; 95% confidence interval [CI], 1.049-1.952), whereas ΔK/dose was not statistically significantly associated with recurrent stone events (HR 1.032; 95% CI, 0.740-1.439). There are clinically meaningful differences in potassium citrate adherence measures. ΔK/dose was more strongly associated with the change in urinary citrate and pH. However, only PDC was significantly associated with recurrent stone events.

Nephrolithiasis is a common condition with several studies documenting an increased prevalence over the past four decades. EAU and AUA guidelines recommend 24-hour urine metabolic evaluation in high-risk stone formers. Aim of this study is to retrospectively evaluate the first three years of experience with LithoTest® (Biohealth Italia Srl, Turin, Italy) through the analysis of demographic, clinical and biochemical data collected from a large cohort of patients with kidney stones. We retrospectively analyzed data from the LithoCenter database, including data from outpatient consultations, between January 2007 and December 2009 from all over Italy. LithoTest® was performed through a 24-hour urine collection and included measurements of urine volume and pH, 24-hour excretion of creatinine as well as main cations and anions, including calcium, magnesium sodium potassium, ammonium, uric acid, oxalate, citrate, phosphate, inorganic sulphate and chloride. Urine state of saturation for calcium oxalate (βCaOx), calcium hydrogen phosphate or brushite (βbsh) and uric acid (βUA) were also calculated by means of the computer program LithoRisk. Brand's test for cystinuria was also carried out. Statistical analysis was performed using the S-PSS software v. 22.0. The number of patients with data available for analysis was 435, of whom 236 were male (54%) and 199 female (46%). Complete 24-hour urine measurements were available for all 435 patients. Compared to men, women had significantly lower values for creatinine, urate, oxalate, phosphate, sodium, potassium, magnesium and chloride excretion, whereas 24-hour pH and citrate excretion were higher. No significant differences were found for the other examined variables. βCaOx and βUA were significantly higher in men than women, whereas no significant difference was found for βbsh. There was a direct relationship between calcium and sodium urine excretion. Excessive sodium excretion was recorded in 191 patients (44%) and low urine volumes in 201 (46.2%). Hyperoxaluria was observed in 118 patients (27.3%), hypercalciuria in 115 (26.6%), hyperuricosuria in 153 (35.4%), hypomagnesuria in 96 (22.2%), and hypocitraturia in 134 patients (31%). Hyperexcretion of sodium, hypocitraturia and hyperoxaluria were most frequent in males. βCaOx was significantly higher in the setting of hypercalciuria, hypocitraturia, hyperoxaluria and urine pH below 5.5. Our findings in a large cohort of high-risk stone-forming patients show significant differences in urinary metabolic profiles between men and women. Carrying on the collection and analysis of data by LithoTest® from 2009 to 2015 and matching urinary and dietary data could eventually improve our understanding on the metabolic profile of stone-formers in Italy.

Correlation Between 24-Hour Urine Protein and Random Urine Protein-Creatinine Ratio in Amyloid Light-Chain Amyloidosis

Urine collection for protein excretion

Dried urine and salivary profiling for complete assessment of cortisol and cortisol metabolites

SUPERSATURATION AND STONE COMPOSITION IN A NETWORK OF DISPERSED TREATMENT SITES

Agreement of Food Records and 24-Hour Urine Studies in Clinical Practice

Prediction of 24-hour protein excretion in pregnancy with a single voided urine protein-to-creatinine ratio

The International Consortium for Quality Research on Dietary Sodium/Salt (TRUE) is a coalition of intentional and national health and scientific organizations formed because of concerns low quality research methods were creating controversy regarding dietary salt reduction. One of the main sources of controversy is believed related to errors in estimating sodium intake with urine studies. The recommendations and positions in this manuscript were generated following a series of systematic reviews and analyses by experts in hypertension, nutrition, statistics and dietary sodium. To assess the population’s current 24-hour dietary sodium ingestion, single complete 24-hour urine samples, collected over a series of days from a representative population sample were recommended. To accurately estimate usual dietary sodium at the individual level, at least 3 non-consecutive complete 24-hour urine collections obtained over a series of days that reflect the usual short-term variations in dietary pattern were recommended. Multiple 24-hour urine collections over several years were recommended to estimate an individuaĺs usual long-term sodium intake. The role of single spot or short duration timed urine collections in assessing population average sodium intake requires more research. Single or multiple spot or short duration timed urine collections are not recommended for assessing an individual’s sodium intake especially in relationship to health outcomes. The recommendations should be applied by scientific review committees, granting agencies, editors and journal reviewers, investigators, policy makers, and those developing and creating dietary sodium recommendations. Low-quality research on dietary sodium/salt should not be funded, conducted, or published.

Metabolic consequences and tubular function after augmentation cystoplasty in children with neurogenic bladder.

Background: Cockcroft-Gault formula (CGF) is the most frequently used formula for calculating creatinine clearance (CrCl) as part of evaluating patients’ eligibility for clinical trial enrollment. However, CGF was originally developed in a different patient population with the main purpose of predicting CrCl measured through 24-hour urine collection. Despite further modifications adjusting for the impact of sex, its ability to accurately predict CrCl in patients with advanced cancers remains controversial. Herein, we looked into the correlations between CrCl calculated using CGF and that estimated using 24-hour urine collection in a cancer patient population that was being evaluated for enrollment in phase 1 clinical trials. Methods: We included patients who were seen in the Department of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center (Houston, TX) and had 24-hour urine collection for estimation of CrCl. We defined CrClactual as that estimated through the 24-hour urine collection and CrClcalculated as that estimated using CGF [(140–age)×(weight in kg)×(0.85 if female)/(72×serum creatinine in mg/dL)]. Underestimation of CrCl was defined as more than 10 mL/minute difference between CrClactual and CrClcalculated. Results: We included 107 patients with advanced cancers who had 24-hour urine creatinine assessments. The concordance correlation coefficient between CrClactual and CrClcalculated was 0.423 (95% CI: 0.271–0.555). The CGF underestimated CrCl in 33% of patients (n=35). In 21 patients who had CrClcalculated of less than 60 mL/minute, the CrClactual was more than 60 mL/minute in 7 patients (33%). In 7 patients who had CrClcalculated of less than 45 mL/minute, the CrClactual was more than 45 mL/minute in 2 patients (29%). Conclusions: The low concordance between CrClactual and CrClcalculated suggests a weak agreement and notable variability. Restricting clinical trial enrollment to patients with CrClcalculated above certain cutoffs would disqualify nearly one third of patients with normal CrCl. Clinical trial eligibility criteria should allow for estimation of CrCl using 24-hour urine collection especially in patients not meeting inclusion criteria based on CGF or other equations alone. Citation Format: Mohamed A. Gouda, Lei Kang, Tin-Yun Tang, Ecaterina E. Dumbrava, Stephane Champiat, Sarina A. Piha-Paul, Paula R. Pohlmann, Aung Naing, Siqing Fu, Apostolia M. Tsimberidou, Jordi Rodon, Timothy A. Yap, Funda Meric-Bernstam, David S. Hong. Discrepancies Between Calculated and Actual Creatinine Clearance: A Phase 1 Trial Unit Experience [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr C063.