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type=\u0022text\/css\u0022 rel=\u0022stylesheet\u0022 href=\u0022\/\/d282kpwvnogo5m.cloudfront.net\/sites\/default\/files\/cdn\/css\/http\/css_Xg7z6oCTVgud_Q0huYz9x9iiD5H_2YPSJ5z2ZViSWdY.css\u0022 media=\u0022all\u0022 \/\u003E\n\u003Clink rel=\u0027stylesheet\u0027 type=\u0027text\/css\u0027 href=\u0027\/sites\/all\/modules\/contrib\/panels\/plugins\/layouts\/onecol\/onecol.css\u0027 \/\u003E\u003C\/head\u003E\u003Cbody\u003E\u003Cdiv class=\u0022panels-ajax-tab-panel panels-ajax-tab-panel-sageoa-tab-art\u0022\u003E\u003Cdiv class=\u0022panel-display panel-1col clearfix\u0022 \u003E\n  \u003Cdiv class=\u0022panel-panel panel-col\u0022\u003E\n    \u003Cdiv\u003E\u003Cdiv class=\u0022panel-pane pane-highwire-markup\u0022 \u003E\n  \n      \n  \n  \u003Cdiv class=\u0022pane-content\u0022\u003E\n    \u003Cdiv class=\u0022highwire-markup\u0022\u003E\u003Cdiv xmlns=\u0022http:\/\/www.w3.org\/1999\/xhtml\u0022 id=\u0022content-block-markup\u0022 xmlns:xhtml=\u0022http:\/\/www.w3.org\/1999\/xhtml\u0022\u003E\u003Cdiv class=\u0022article fulltext-view \u0022\u003E\u003Cspan class=\u0022highwire-journal-article-marker-start\u0022\u003E\u003C\/span\u003E\u003Cdiv class=\u0022section abstract\u0022 id=\u0022abstract-1\u0022\u003E\u003Ch2\u003ESummary\u003C\/h2\u003E\n            \u003Cp id=\u0022p-1\u0022\u003EThe prevalence of kidney stones has been increasing over time. A patient-centered approach to diagnosis and management of kidney stones includes correct interpretation of 24-hour urine samples, selection of dietary and pharmacologic interventions based on their risk\/benefit profile, and recognition of rare genetic forms of kidney stones. This article discusses the epidemiology of kidney stones, interpretation of 24-hour urine chemistries to inform clinical practice, approaches to calcium phosphate stones and staghorn calculi, and conditions that can be associated with nephrolithiasis.\u003C\/p\u003E\n         \u003C\/div\u003E\u003Cul class=\u0022kwd-group\u0022\u003E\u003Cli class=\u0022kwd\u0022\u003ENephrolithiasis\u003C\/li\u003E\u003C\/ul\u003E\u003Cul class=\u0022kwd-group clinical-trial\u0022\u003E\u003Cli class=\u0022kwd\u0022\u003ENephrolithiasis\u003C\/li\u003E\u003Cli class=\u0022kwd\u0022\u003ENephrology\u003C\/li\u003E\u003C\/ul\u003E\u003Cdiv class=\u0022section\u0022 id=\u0022sec-1\u0022\u003E\n         \n         \u003Cp id=\u0022p-2\u0022\u003EThe prevalence of kidney stones has been increasing over time. A patient-centered approach to diagnosis and management of kidney stones includes correct interpretation of 24-hour urine samples, selection of dietary and pharmacologic interventions based on their risk\/benefit profile, and recognition of rare genetic forms of kidney stones.\u003C\/p\u003E\n         \u003Cp id=\u0022p-3\u0022\u003EGary C. Curhan, MD, ScD, Brigham and Women\u0027s Hospital, Boston, Massachusetts, USA, discussed the epidemiology of kidney stones. He based much of his talk on data derived from 3 large cohort studies, 2 female Nurses\u0027 Health Studies (NHS I and II) [Harvard School of Public Health], and the male cohort Health Professionals Follow-Up Study (HPFS) [Harvard School of Public Health].\u003C\/p\u003E\n         \u003Cp id=\u0022p-4\u0022\u003EThe lifetime risk of nephrolithiasis in the United States currently approaches 10% to 12% for men and 7% for women. In addition to age and sex, risk factors include diet and systemic conditions such as Crohn disease, hyperparathyroidism, obesity, hypertension, diabetes, chronic kidney disease (CKD), and cardiovascular disease (CVD).\u003C\/p\u003E\n         \u003Cp id=\u0022p-5\u0022\u003EDietary determinants that increase stone formation include oxalate, sugars, sodium, vitamin C, and calcium supplements. Higher dietary intake of calcium, potassium, magnesium, and beverages such as coffee and tea are associated with reduced risk. The type of dietary calcium (dairy vs nondairy) does not seem to influence stone formation, but a low-calcium diet is associated with a higher risk of stone formation. On the other hand, why supplemental calcium is associated with higher risk is not known. The Dietary Approaches to Stop Hypertension (DASH) diet reduces hypertension [Harrington JM et al. \u003Cem\u003EAm J Hypertens\u003C\/em\u003E. 2013], and the DASH score is inversely related to stone risk (\u003Cem\u003EP\u003C\/em\u003E \u0026lt; .001) [Taylor EN et al. \u003Cem\u003EJ Am Soc Nephrol\u003C\/em\u003E. 2009].\u003C\/p\u003E\n         \u003Cp id=\u0022p-6\u0022\u003EStone formation increases as weight or body mass index increases. However, weight loss and physical activity have not yet been shown to have an effect on the relative risk of stone formation. Diabetes is associated with increased risk of stone formation independent of obesity [Taylor EN et al. \u003Cem\u003EKidney Int.\u003C\/em\u003E 2005].\u003C\/p\u003E\n         \u003Cp id=\u0022p-7\u0022\u003ENephrolithiasis may increase the risk for CKD and end-stage renal disease, possibly via shared risk factors. The association with CVD appears to occur in women\u2014but not men\u2014in the US cohorts and was higher in women than men in a Canadian study [Alexander RT et al. \u003Cem\u003EClin J Am Soc Nephrol\u003C\/em\u003E. 2013].\u003C\/p\u003E\n         \u003Cp id=\u0022p-8\u0022\u003EDr Curhan said that the traditional definitions of hypercalciuria and hyperoxaluria are \u201cmade up\u201d and arbitrary, as urinary calcium and oxalate excretion linearly increase the risk of stones. With no threshold, even so-called normal concentrations of urine calcium and oxalate are still associated with some risk. In Curhan\u0027s studies, uric acid excretion was not associated with increased stone risk; in fact, in some cohorts it was protective. The role of urinary uric acid in promoting calcium stone formation is therefore unclear [Toka HR et al. \u003Cem\u003EPLoS One\u003C\/em\u003E 2013].\u003C\/p\u003E\n         \u003Cp id=\u0022p-9\u0022\u003EJohn R. Asplin, MD, Litholink Corporation, Chicago, Illinois, USA, discussed interpretation of 24-hour urine chemistries to inform clinical practice. The American Urological Association (AUA) Guidelines were recently updated [Pearle MS et al. \u003Cem\u003EJ Urol\u003C\/em\u003E. 2014] and call for metabolic testing for high-risk or interested first-time stone formers and recurrent stone formers, consisting of 1, or preferably 2, 24-hour urine collections obtained on a random diet and analyzed at minimum for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine. This guideline is based on expert opinion rather than data. Dr Asplin adds chloride, magnesium, phosphorus, urea nitrogen, sulfate, ammonium, and osmolarity to these tests, enabling a supersaturation calculation.\u003C\/p\u003E\n         \u003Cp id=\u0022p-10\u0022\u003EDiet, supplements\/medications, and location (work vs home) can all affect 24-hour urine collection; by looking at creatinine excretion in paired samples\u2014which should be similar\u2014the reliability of the test is improved and other values can be interpreted. The percentage of patients with a 25% or 50% variability between 2 consecutive 24-hour urine samples (n = 2000 pairs of samples) is shown in \u003Ca id=\u0022xref-table-wrap-1-1\u0022 class=\u0022xref-table\u0022 href=\u0022#T1\u0022\u003ETable 1\u003C\/a\u003E [Asplin JR. \u003Cem\u003ESemin Nephrol\u003C\/em\u003E. 2008].\u003C\/p\u003E\n         \u003Cdiv id=\u0022T1\u0022 class=\u0022table pos-float\u0022\u003E\u003Cdiv class=\u0022table-inline\u0022\u003E\u003Cdiv class=\u0022callout\u0022\u003E\u003Cspan\u003EView this table:\u003C\/span\u003E\u003Cul class=\u0022callout-links\u0022\u003E\u003Cli class=\u00220 first\u0022\u003E\u003Ca href=\u0022\/\u0022 class=\u0022table-expand-inline\u0022 data-table-url=\u0022\/highwire\/markup\/15300\/expansion?postprocessors=highwire_figures%2Chighwire_math%2Chighwire_inline_linked_media%2Chighwire_embed\u0026amp;table-expand-inline=1\u0022 html=\u00221\u0022 fragment=\u0022#\u0022 external=\u00221\u0022 data-icon-position=\u0022\u0022 data-hide-link-title=\u00220\u0022\u003EView inline\u003C\/a\u003E\u003C\/li\u003E\u003Cli class=\u00221\u0022\u003E\u003Ca href=\u0022\/highwire\/markup\/15300\/expansion?width=1000\u0026amp;height=500\u0026amp;iframe=true\u0026amp;postprocessors=highwire_figures%2Chighwire_math%2Chighwire_inline_linked_media\u0022 class=\u0022colorbox colorbox-load table-expand-popup\u0022 rel=\u0022gallery-fragment-tables\u0022 data-icon-position=\u0022\u0022 data-hide-link-title=\u00220\u0022\u003EView popup\u003C\/a\u003E\u003C\/li\u003E\u003Cli class=\u00222 last\u0022\u003E\u003Ca href=\u0022\/highwire\/powerpoint\/15300\u0022 class=\u0022highwire-figure-link highwire-figure-link-ppt\u0022 data-icon-position=\u0022\u0022 data-hide-link-title=\u00220\u0022\u003EDownload powerpoint\u003C\/a\u003E\u003C\/li\u003E\u003C\/ul\u003E\u003C\/div\u003E\u003C\/div\u003E\u003Cdiv class=\u0022table-caption\u0022\u003E\u003Cspan class=\u0022table-label\u0022\u003ETable 1.\u003C\/span\u003E \n               \u003Cp id=\u0022p-11\u0022 class=\u0022first-child\u0022\u003EPercentage of Patients With a 25% or 50% Variability Between 2 Consecutive 24-hour Urine Samples\u003C\/p\u003E\n            \u003Cdiv class=\u0022sb-div caption-clear\u0022\u003E\u003C\/div\u003E\u003C\/div\u003E\u003C\/div\u003E\n         \u003Cp id=\u0022p-13\u0022\u003EFollow-up samples should be tested at 6-month or yearly intervals. The cause of any changes, particularly if unexpected, should be investigated. Fluid intake can vary widely, and patients should be encouraged to maintain a high fluid intake. Patient adherence to recommendations can be tracked, and the urine chemistry can be a more reliable indicator of diet than a history.\u003C\/p\u003E\n         \u003Cp id=\u0022p-14\u0022\u003ESupersaturation may be suggestive of the type of stone in the absence of stone analysis. Reduction of supersaturation can decrease stone formation, although it is easier to achieve for uric acid stones than for calcium oxalate stones.\u003C\/p\u003E\n         \u003Cp id=\u0022p-15\u0022\u003EDavid S. Goldfarb, MD, New York University Langone Medical Center, New York, New York, USA, continued the discussion by presenting approaches to calcium phosphate stones and staghorn calculi. A staghorn calculus is a branched stone that occupies a large portion of the collecting system. It is associated with high urine pH, can cause loss of kidney function, and can be asymptomatic.\u003C\/p\u003E\n         \u003Cp id=\u0022p-16\u0022\u003EOlder guidelines suggested surgical management using percutaneous nephrolithotomy monotherapy or in combination with shock wave lithotripsy (SWL). SWL monotherapy or open surgery are no longer appropriate. Nephrectomy should be considered when the involved kidney has negligible function, such as if it provides \u0026lt; 10% of total glomerular filtration rate. Ureteroscopy (URS) is being used more often, particularly by younger practitioners with more skills, which, he speculated, were acquired from video gaming.\u003C\/p\u003E\n         \u003Cp id=\u0022p-17\u0022\u003EAUA guidelines suggest that when a stone is available, clinicians should obtain a stone analysis at least once [Pearle MS et al. \u003Cem\u003EJ Urol\u003C\/em\u003E. 2014]. Stone composition of uric acid, cystine, or struvite implicates specific metabolic or genetic abnormalities, and knowledge of composition may help direct preventive measures. In type I renal tubular acidosis alkali is beneficial; potassium citrate therapy may prevent recurrent calcium stone formation, as can increased fluid intake.\u003C\/p\u003E\n         \u003Cp id=\u0022p-18\u0022\u003EJohn C. Lieske, MD, Mayo Clinic, Rochester, Minnesota, USA, described a number of conditions\u2014some rare\u2014that can be associated with nephrolithiasis, including primary hyperparathyroidism, immobilization, Paget disease, and hyperthyroidism. Genetic predispositions to nephrolithiasis have been suggested, because half of first-degree relatives with stones are also affected.\u003C\/p\u003E\n         \u003Cp id=\u0022p-19\u0022\u003EEnteric hyperoxaluria is caused by fat malabsorption, which commonly follows bariatric surgery, and leads to calcium oxalate stones. These stones can be treated with fluids, a low-fat diet, a low-oxalate diet, and a moderate amount of calcium as an oxalate binder.\u003C\/p\u003E\n         \u003Cp id=\u0022p-20\u0022\u003ERare causes of kidney stones should be suspected in those with a first stone as a preadolescent or in those with acute kidney injury, growth retardation, and a family history of stones, nephrocalcinosis, or unexplained kidney failure. Crystals in the urine may be pathognomonic. Reddish brown, circular crystals are suggestive of adenine phosphoribyltransferase (APRT) deficiency. Other diagnostic tests should include urine protein (low molecular weight proteinuria in younger men plus hypercalciuria suggests Dent disease and should lead to testing for retinol binding protein) and medical imaging (radiolucent stones plus alkaline urine pH suggest APRT deficiency).\u003C\/p\u003E\n         \u003Cp id=\u0022p-21\u0022\u003ERecently identified links between diabetes, obesity, CKD, and hypertension with kidney stones highlight the importance of correctly identifying the cause of an individual patient\u0027s stones, initiating proper treatment, and continuing therapy to minimize recurrences.\u003C\/p\u003E\n      \u003C\/div\u003E\u003Cul class=\u0022copyright-statement\u0022\u003E\u003Cli class=\u0022fn\u0022 id=\u0022copyright-statement-1\u0022\u003E\u00a9 2015 MD Conference Express\u00ae\u003C\/li\u003E\u003C\/ul\u003E\u003Cspan class=\u0022highwire-journal-article-marker-end\u0022\u003E\u003C\/span\u003E\u003C\/div\u003E\u003Cspan id=\u0022related-urls\u0022\u003E\u003C\/span\u003E\u003C\/div\u003E\u003Ca href=\u0022http:\/\/mdc.sagepub.com\/content\/14\/49\/25.abstract\u0022 class=\u0022hw-link hw-link-article-abstract\u0022 data-icon-position=\u0022\u0022 data-hide-link-title=\u00220\u0022\u003EView Summary\u003C\/a\u003E\u003C\/div\u003E  \u003C\/div\u003E\n\n  \n  \u003C\/div\u003E\n\u003C\/div\u003E\n  \u003C\/div\u003E\n\u003C\/div\u003E\n\u003C\/div\u003E\u003Cscript type=\u0022text\/javascript\u0022 src=\u0022http:\/\/mdc.sagepub.com\/sites\/all\/modules\/highwire\/highwire\/plugins\/highwire_markup_process\/js\/highwire_openurl.js?nzlu9d\u0022\u003E\u003C\/script\u003E\n\u003Cscript type=\u0022text\/javascript\u0022 src=\u0022http:\/\/mdc.sagepub.com\/sites\/all\/modules\/highwire\/highwire\/plugins\/highwire_markup_process\/js\/highwire_tables.js?nzlu9d\u0022\u003E\u003C\/script\u003E\n\u003C\/body\u003E\u003C\/html\u003E"}