Faculty Bibliography

Temperature and relative humidity have opposing effects on evaporative water loss, the likely mediator of the temperature-dependence of nephrolithiasis. However, prior studies considered only dry-bulb temperatures when estimating the temperature-dependence of nephrolithiasis. We used distributed lag non-linear models and repeated 10-fold cross-validation to determine the daily temperature metric and corresponding adjustment for relative humidity that most accurately predicted kidney stone presentations during hot and cold periods in South Carolina from 1997 to 2015. We examined three metrics for wet-bulb temperatures and heat index, both of which measure the combination of temperature and humidity, and for dry-bulb temperatures: (1) daytime mean temperature; (2) 24-h mean temperature; and (3) most extreme 24-h temperature. For models using dry-bulb temperatures, we considered four treatments of relative humidity. Among 188,531 patients who presented with kidney stones, 24-h wet bulb temperature best predicted kidney stone presentation during summer. Mean cross-validated residuals were generally lower in summer for wet-bulb temperatures and heat index than the corresponding dry-bulb temperature metric, regardless of type of adjustment for relative humidity. Those dry-bulb models that additionally adjusted for relative humidity had higher mean residuals than other temperature metrics. The relative risk of kidney stone presentations at the 99th percentile of each temperature metric compared to the respective median temperature in summer months differed by temperature metric and relative humidity adjustment, and ranged from an excess risk of 8-14%. All metrics performed similarly in winter. The combination of temperature and relative humidity determine the risk of kidney stone presentations, particularly during periods of high heat and humidity. These results suggest that metrics that measure moist heat stress should be used to estimate the temperature-dependence of kidney stone presentations, but that the particular metric is relatively unimportant.

Because salicylism is a clinical diagnosis, the serum concentration should be interpreted in conjunction with the clinical presentation. A 26-year-old man presented to the Emergency Department with abdominal painand had extremely elevated serum triglycerides (>7000 mg/dL). Ethanol, acetaminophen, and salicylate concentrations were checked because of concern of self-injurious behavior, which returned at 13.1 mg/dL, undetectable, and >100 mg/dL, respectively. His basic metabolic panel revealed a bicarbonate of 23 mEq/L and an anion gap of 11. An arterial blood gas showed a pH 7.39 and a PCO2 of 36.6 mmHg. On physical examination, he was awake and alert, and had a respiratory rate of 12–14/min. The possible effect of hyperlipidemia to falsely elevate the salicylate concentration was recognized. He was treated for severe hypertriglyceridemia and as his triglyceride level dropped, his repeat salicylate concentration was <1 mg/dL. Since dfferent sized lipoproteins contribute variably to serum sample turbiditythey have the potential to interfere with the absorption of light thereby producing erroneous laboratory results . Clinicians need to be aware of the implications of severe hyperlipidemia and interference to prevent clinical errors based on false positive laboratory results

INTRODUCTION/BACKGROUND:Adenine phosphoribosyltransferase (APRT) deficiency is a rare, but significant, cause of kidney stones and progressive chronic kidney disease. The optimal treatment has not been established. The purpose of this pilot study was to compare the effect of the xanthine oxidoreductase inhibitors allopurinol and febuxostat on urinary 2,8-dihydroxyadenine (DHA) excretion in APRT deficiency patients. MATERIALS AND METHODS/METHODS:Patients listed in the APRT Deficiency Registry of the Rare Kidney Stone Consortium, currently receiving allopurinol therapy, were invited to participate. The trial endpoint was the 24-h urinary DHA excretion following treatment with allopurinol (400mg/day) and febuxostat (80mg/day). Urinary DHA was measured using a novel ultra-performance liquid chromatography - electrospray tandem mass spectrometry assay. RESULTS:Eight of the 10 patients invited completed the study. The median (range) 24-h urinary DHA excretion was 116 (75-289) mg at baseline, and 45 (13-112) mg after 14days of allopurinol therapy (P=0.036). At the end of the febuxostat treatment period, 4 patients had urinary DHA below detectable limits (<20ng/mL) compared with none of the participants following allopurinol treatment (P=0.036). The other 4 participants had a median 24-h urinary DHA excretion of 13.2 (10.0-13.4) mg at the completion of febuxostat therapy (P=0.036). CONCLUSION/CONCLUSIONS:Urinary DHA excretion in APRT deficiency patients decreased with conventional doses of both allopurinol and febuxostat. Febuxostat was, however, significantly more efficacious than allopurinol in reducing DHA excretion in the prescribed doses. This finding, which may translate into improved outcomes of patients with APRT deficiency, should be confirmed in a larger sample.

Patients with complex chronic diseases usually must make multiple lifestyle changes to limit and manage their conditions. Numerous studies have shown that education alone is insufficient for engaging people in lifestyle behavior change, and that theory-based behavioral approaches also are necessary. However, even the most motivated individual may have difficulty with making lifestyle changes because of the information complexity associated with multiple behavior changes. The goal of the current Healthy Hearts and Kidneys study was to evaluate, different mobile health (mHealth)-delivered intervention approaches for engaging individuals with type 2 diabetes (T2D) and concurrent chronic kidney disease (CKD) in behavior changes. Participants were randomized to 1 of 4 groups, receiving: (1) a behavioral counseling, (2) technology-based self-monitoring to reduce information complexity, (3) combined behavioral counseling and technology-based self-monitoring, or (4) baseline advice. We will determine the impact of randomization assignment on weight loss success and 24-hour urinary excretion of sodium and phosphorus. With this report we describe the study design, methods, and approaches used to assure information security for this ongoing clinical trial. Clinical Trials.gov Identifier: NCT02276742.

Background: The assessment of HRQoL in RKSF is important for following disease course and evaluating treatment. Previously, using a non-disease specific instrument we showed that RKSF present differently, with the worst domain scores in cystinuria. These are the first follow-up data based on summary scores for adults in a cross-sectional comparison.
Method(s): RKSF were enrolled from 4 RKSC registries: primary hyperoxaluria, cystinuria, Dent disease and APRTd. HRQoL is measured with the generic non-disease specific SF-36v2. Results are norm-based scores (NBS) based on US Standard Population (Domain score mean = 50). Group means < 47 indicate the presence of impaired functioning in associated dimension.
Result(s): We scored 545 surveys of the adult population at different time points, adjusted for the last stone event and compared the Physical and Mental Component Scores (PCS and MCS). We found the lowest PCS in Dent, and the highest in PH. The lowest MCS was found in cystinuria, the highest was found in PH. Low PCS indicate restrictions in self-care, physical, social and role activities; bodily pain, tiredness and poor rated health. Low MCS are associated with frequent psychological distress, social and role disability due to emotional problems, and poor rated health. Participants with cystinuria reported more stone events with related procedures than other RKSF (X2 (9) 23.375, p=.005).
Conclusion(s): HRQoL in RKSF is influenced by stone events and can be assessed with a non-disease specific SF-36v2. Adjusting for time between the survey and last event allows for the interpretation of more meaningful HRQoL profiles. The time from the last stone event and related procedures affect HRQOL in RKSF significantly. (Table Presented)

Background: USD is a preventable disease characterized by significant risk of recurrence. A "cascade of care" shows how many patients are lost to follow-up at diagnosis, referral, and treatment and is a useful tool in delivering HIV care. We can analyze our success, or failure, in the secondary prevention of kidney stones and retention of patients by constructing a cascade of care.
Method(s): We abstracted data from observational studies to identify impediments to care of patients with USD Results: In the US there are about 1.2 million ER visits per year. 37% of patients diagnosed with stones receive a follow-up consultation with a urologist and fewer see a nephrologist. Although 24h urine collection results may decrease stone recurrence rate, only 7.4% do them. 50% of patients experience a recurrent 2nd episode within 5 years. Of these 24% undergo a complete evaluation, 18% are referred to a nephrologist and 13.8% are prescribed medical therapy. 30% remain adherent to this pharmacotherapy. Of patients that are adherent 27% have lower odds of an ER visit than non-adherent patients. The cascade of care demonstrates that a low prevalence of patients receive proper followup. The impediments to the care of patients with kidney stones are (1) the unrecognized comorbidities of stones (2) disconnect between the ER and stone experts and (3) the low prevalence of 24h urine collections and prescribed medical therapy.
Conclusion(s): It is important to identify loci in the cascade of care that could represent opportunities to change practice. Prescription of appropriate fluid therapy and dietary changes and a referral to an expert should 1st be initiated by the ER. The low prevalence of 24h urine collections may reflect that the data are intimidating for some. Empiric therapy for calcium stones with fluids, diet, thiazides and potassium citrate may be a rational therapy to achieve significant supersaturation reductions and could be compared with targeted medical therapy in a randomized controlled trial. A greater effort needs to be devoted to develp a comprehensive flow of participants to retain patients in the cascade of care for USD. (Table Presented)

Background: Urine chemistry is a determinant of stone formation in cystinuria. We previously showed that positive cystine capacity (CysCap), a measure of higher cystine solubility, led to fewer stone events. We queried the RKSC Cystinuria Registry to determine urinary and medication variables associated with positive (CysCap+), rather than negative (CysCap-) values.
Method(s): This is the 1st report from the Cystinuria Registry, with data on 300 people with cystinuria (142 males, 158 females; age at enrollment 38 +/- 17 years). 112 participants had 306 determinations of CysCap, measured by Litholink (Chicago, IL). In this cross-sectional study we compared variables associated with CysCap+ vs CysCap-.
Result(s): Lower urine Na (r=0.48; Fig 1A) and creatinine (r=0.62, not shown) were associated with lower 24h urine cystine (UC; P<0.001). Increasing CysCap values were seen with increasing urine pH (rs=0.45, Fig 1B), volume (rs=0.44) and decreasing UC (rs=-0.44 Fig 1C; all P<0.001). Dividing Cyscap determinations into CysCap+ and CysCapgroups (Table), only higher urine volume and greater daily citrate doses were different. Relatively few participants were taking citrate or tiopronin.
Conclusion(s): Higher urine pH and volume and lower UC were associated with less lithogenic urine; lower UC was seen with less Na and creatinine. Higher volume and citrate doses distinguished patients with less lithogenic urine. Many patients with cystinuria may be undertreated and would benefit from better dietary adherence. (Table Presented)

Background: Multiple bacterial species are capable of degrading oxalate in vitro. Certain taxa degrade oxalate as their sole source of energy and carbon (e.g. Oxalobacter formigenes), whereas others use oxalate as an auxiliary carbon source. For oxalate metabolism, it is not yet well-understood how genomic potential relates to transcriptional regulation. We asked whether the human gut could have a community of oxalatedegrading taxa working synergistically to diminish the effects of this toxic metabolite. Our hypothesis is that oxalate metabolism is regulated by a multi-organism oxalatedegrading community (oxalobiome) that is dominated by specialist oxalate degraders.
Method(s): We used data from 2 public databases: (i)8 healthy subjects in the USA; and (ii)471 healthy subjects in the Netherlands as part of the Human Functional Genomic Project (HFGP). Both collected fecal samples for metagenomic and/or metatranscriptomic high throughput sequencing. Using HUMAnN2 with customized settings, we profiled the metabolic activity of oxalate-degrading bacterial species. Output from these analyses was expressed as Reads per Kilobase per Million mapped reads (RPKM).
Result(s): We identified the oxalate degradation pathway (ODP) in the metagenome and metatranscriptome of all 8 subjects. Mean ODP is 35.3+/-28.1 and 90.1+/-43.5 RPKM in the metagenome and the metatranscriptome, respectively, indicating active expression. O. formigenes, E. coli, and unclassified bacteria were present in metagenomic and metatranscriptomic reads. B. dentium had detectable ODP in its genome but was not transcribing it. In the HFGP database, we identified ODP in 328 subjects of the 471 tested (70%) (Mean=18.1+/-2.1 RPKM). ODP was detected in B. animalis, B. dentium, B. pseudocatenulatum, E.coli/Shigella, L. acidophilus, L. gasseri, L. mucosae, O. formigenes and unclassified bacteria. ODP was examined in the metagenome of 265 females (Mean ODP= 21.7+/-3.3) and 200 males (Mean ODP=13.3+/-1.9 RPKM; p=0.04 by unpaired t test).
Conclusion(s): We have identified a community of bacteria with the potential to degrade oxalate in healthy humans and species actively transcribing ODP. These include E.coli, which might be a common contributor of oxalate degradation in humans. The sex differences in ODP is consistent with the ~ 2:1 male/female incidence and prevalence of calcium oxalate stones