The ROKS nomogram for predicting a second symptomatic stone episode

Water for preventing urinary stones

BACKGROUND

Urinary stone disease is a common condition characterised by increasing prevalence and high rates of recurrence. Observational studies have reported that increased water intake played a role in the prevention of urinary stone formation but with limited strength of evidence.

OBJECTIVES

To compare the effects of increased water intake with standard water intake for the prevention of urinary stone formation in participants with or without a history of urinary stones.

SEARCH METHODS

We performed a systematic search of PubMed (MEDLINE), EMBASE (Ovid) and the Cochrane Library to 15 October 2019. We handsearched review articles, clinical trial registries, and reference lists of retrieved articles. We did not apply any restrictions to publication language or publication status.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs looking at the benefits and harms of increased water intake versus standard water intake for the prevention of urinary stone formation in participants with or without a history of urinary stones.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently extracted data and assessed the risk of bias of included studies. We pooled dichotomous outcomes (e.g. incidence/recurrence rate of urinary stones; adverse events) using risk ratios (RRs) with 95% confidence intervals (CIs). We calculated hazard ratio (HRs) and corresponding 95% CIs to assess the intervention effect for time-to-event outcomes. We assessed the certainty of the evidence by using the GRADE criteria.

MAIN RESULTS

Our search identified no RCTs investigating the role of increased water intake for the prevention of urinary stone formation in participants with no history of urinary stones (primary prevention). We found one RCT assessing the effects of increased water intake versus standard water intake for the prevention of urinary stone formation in people with a history of urinary stones (secondary prevention). This trial randomised 220 participants (110 participants in the intervention group with increased water intake and 110 in the control group with standard water intake). Increased water intake was defined as achieving a urine volume of at least 2.0 L per day by drinking water. Based on this study, increased water intake may decrease stone recurrences (RR 0.45, 95% CI 0.24 to 0.84; 199 participants; low-certainty evidence); this corresponds to 149 fewer (43 fewer to 205 fewer) stone recurrences per 1000 participants with 270 stone recurrence per 1000 participants over five years in the control group. Increased water intake may also prolong the time to urinary stone recurrence compared to standard water intake (HR 0.40, 95% CI 0.20 to 0.79; 199 participants; low-certainty evidence); based on a stone recurrence rate of 270 per 1000 participants over five years, this corresponds to 152 fewer (209 fewer to 50 fewer) recurrences per 1000 participants. For both outcomes we downgraded the certainty of evidence for study limitations and imprecision. We found no evidence for the outcome of adverse events AUTHORS' CONCLUSIONS: We found no RCT evidence on the role of increased water intake for primary prevention of urinary stones. For secondary prevention, increased water intake achieving a urine volume of at least 2.0 L/day may reduce urinary stone recurrence and prolong time to recurrence for people with a history of urinary stone disease. However, our confidence in these findings is limited. We did not find evidence for adverse events.

Differences in national and international guidelines regarding use of kidney stone formers as living kidney donors

PURPOSE OF REVIEW

Traditionally, nephrolithiasis was considered a relative contraindication to kidney donation because of a risk of recurrent stones in donors and adverse stone-related outcomes in recipients. However, the scarcity of organs has driven the transplant community to re-examine and broaden selection criteria for living donors with stones. In this review, we summarize and contrast the guidelines published by various prominent national and international societies on this topic.

RECENT FINDINGS

Although recent iterations of living donor guidelines are less stringent with respect to nephrolithiasis than those published in the 1990s, there is little consensus among national and international transplant society guidelines regarding selection criteria for potential kidney donors with nephrolithiasis.

SUMMARY

The lack of evidence-based guidelines deters transplant centers from implementing selection criteria to accept donors with nephrolithiasis and discourages studies of outcomes in donors with nephrolithiasis and their recipients. In addition to drawing attention to the disparities in prevailing guidelines, we put forth several questions that must be answered before generalizable criteria for selection of donor with nephrolithiasis can be developed.

Metabolic Surgery to Treat Obesity in Diabetic Kidney Disease, Chronic Kidney Disease, and End-Stage Kidney Disease; What Are the Unanswered Questions?

Obesity is a major factor in contemporary clinical practice in nephrology. Obesity accelerates the progression of both diabetic and non-diabetic chronic kidney disease and, in renal transplantation, both recipient and donor obesity increase the risk of allograft complications. Obesity is thus a major driver of renal disease progression and a barrier to deceased and living donor kidney transplantation. Large observational studies have highlighted that metabolic surgery reduces the incidence of albuminuria, slows chronic kidney disease progression, and reduces the incidence of end-stage kidney disease over extended follow-up in people with and without type 2 diabetes. The surgical treatment of obesity and its metabolic sequelae has therefore the potential to improve management of diabetic and non-diabetic chronic kidney disease and aid in the slowing of renal decline toward end-stage kidney disease. In the context of patients with end-stage kidney disease, although complications of metabolic surgery are higher, absolute event rates are low and it remains a safe intervention in this population. Pre-transplant metabolic surgery increases access to kidney transplantation in people with obesity and end-stage kidney disease. Metabolic surgery also improves management of metabolic complications post-kidney transplantation, including new-onset diabetes. Procedure selection may be critical to mitigate the risks of oxalate nephropathy and disruption to immunosuppressant pharmacokinetics. Metabolic surgery may also have a role in the treatment of donor obesity, which could increase the living kidney donor pool with potential downstream impact on kidney paired exchange programmes. The present paper provides a comprehensive coverage of the literature concerning renal outcomes in clinical studies of metabolic surgery and integrates findings from relevant mechanistic pre-clinical studies. In so doing the key unanswered questions for the field are brought to the fore for discussion.

Diversity of Phenotype and Genetic Etiology of 23 Cystinuria Saudi Patients: A Retrospective Study

Background: Cystinuria is an inborn error of metabolism that manifests with renal stones due to defective renal epithelial cell transport of cystine which resulted from pathogenic variants in the SLC3A1 and/or SLC7A9 genes. Among nephrolithiasis diseases, cystinuria is potentially treatable, and further stone formation may be preventable. We report 23 patients who were identified biochemically and genetically to have cystinuria showing the diversity of the phenotype of cystinuria and expanding the genotype by identifying a broad spectrum of mutations. Patients and Methods: This is a multicenter retrospective chart review, where clinical and biochemical data, genetic analysis and the progress of the disease were documented over five years at two centers from 2014 to 2019. Results: Of 23 patients who were identified biochemically and/or genetically to have cystinuria, 14 (62%) were male. Thirteen patients were homozygous, and two were heterozygous for the SLC3A1 gene. Seven were homozygous and one was compound heterozygous for the SLC7A9 gene. We have detected 12 genetic variants including five novel variants. SLC3A1 gene variant c.1400 T > A (p.Met467Lys) is found in 38% of our cohort. Although 21 patients required surgical intervention, none developed ESRD. The number of stone episodes per year varied widely (median frequency of 0.45 stones/ per year, range between 0.06 and 78.2), with no significant difference in stone events per year between sexes (P = 0.73). Conclusion: Despite the high rate of consanguinity in Saudi Arabia, there was a broad spectrum of genetic variants. Most of our patients are homozygous recessive for SLC genes with multiple generations affected which indicates early screening and prevention of disease in these families. Phenotypic heterogeneity is well documented in our cohort even with the same genotype and the first stone episode age was variable but most commonly seen in the first decade of life.

Automatic detection of calcium phosphate deposit plugs at the terminal ends of kidney tubules

Kidney stones are a common urologic condition with a high amount of recurrence. Recurrence depends on a multitude of factors the incidence of precursors to kidney stones, plugs, and plaques. One method of characterising the stone precursors is endoscopic assessment, though it is manual and time-consuming. Deep learning has become a popular technique for semantic segmentation because of the high accuracy that has been demonstrated. The present Letter examined the efficacy of deep learning to segment the renal papilla, plaque, and plugs. A U-Net model with ResNet-34 encoder was tested; the Letter examined dropout (to avoid overtraining) and two different loss functions (to address the class imbalance problem. The models were then trained in 1666 images and tested on 185 images. The Jaccard-cross-entropy loss function was more effective than the focal loss function. The model with the dropout rate 0.4 was found to be more effective due to its generalisability. The model was largely successful at delineating the papilla. The model was able to correctly detect the plaques and plugs; however, small plaques were challenging. Deep learning was found to be applicable for segmentation of an endoscopic image for the papilla, plaque, and plug, with room for improvement.

[A mobile app for patients suffering from kidney stones]

BACKGROUND AND OBJECTIVES

Kidney stone disease has become an important worldwide socioeconomic issue. However, metaphylaxis fails due to low compliance rates. Therefore, we developed a mobile app (StoneMD: Kidney Stones) for patients with kidney stones to increase compliance in stone metaphylaxis.

MATERIALS AND METHODS

To identify the most appropriate design of the app, we searched through the App Store and the Google Play Store and integrated the clinical recommendations of the European Association of Urology (EAU) and the American Urological Association (AUA). To test the value of this app, a questionnaire was developed in which the patient should answer questions about the drinking behavior and the subjective use of the app in the field of metaphylaxis.

RESULTS

StoneMD: Kidney Stones offers the opportunity to calculate the individual risk of a new stone episode. In addition, the app offers several features to raise awareness of lifestyle modification, including hydration as metaphylaxis of urolithiasis, reminder of inserted ureteral stents and document the self-measured urine pH. A total of 49 patients participated in the questionnaire: 89.8% (n = 46) of these patients had a smartphone, 73.9% reported a daily intake of <2.5 l, 76.5% of these patients believe that their drinking behavior is positively influenced by the app, 71.7% stated that the app for relapse prevention is more suitable than traditional information brochures, 56.5% want to continue to use the app.

CONCLUSIONS

StoneMD: Kidney Stones is the first mobile app for stone metaphylaxis. StoneMD might help to improve patient compliance and might lower the risk of stone formation.

National Trends in CT Utilization and Estimated CT-related Radiation Exposure in the Evaluation and Follow-up of Stone Patients

OBJECTIVE

To describe trends in computed tomography (CT) use and estimate the radiation exposure among stone formers using a national insurance claims database.

METHODS

Within MarketScan, adult stone patients from 2007 to 2013 were identified using International Classification of Diseases-Revision 9, International Classification of Diseases-Revision 10, and Current Procedural Terminology codes. Patients were classified as "active" (≥2 diagnosis codes for nephrolithiasis, or receipt of stone surgery) or "inactive" (1 stone diagnosis) and compared to age- and gender-matched controls. CT utilization was tracked over 3 years for each group. Annual CT-related radiation exposure was estimated using previously published dose values and compared using Kruskal-Wallis and χ² tests. Demographic factors associated with greater CT exposure were identified on multivariate logistic regression.

RESULTS

Of active stone patients, 112,140 underwent surgery and 215,376 were managed nonoperatively. There were 175,228 inactive stone patients and 502,744 controls. On average, active stone patients received nearly 10 times as many CTs as controls at 3 years (P <.001), and more acute imaging (P <.001). About 25% and 15% of operative and nonoperative patients, respectively, received ≥3 CTs in 3 years. This was associated with female gender. For nonoperative patients, this was also associated with age, residence in the North-Central or South regions, and inversely associated with metropolitan residence (all P <.01). Over 10% of active stone patients are estimated to receive >20 mSv in the first year alone.

CONCLUSION

CT use and nonsurgical radiation exposure for active stone patients is significant. Over 10% are estimated to exceed occupational limits in the first year. Judicious CT imaging and low-dose protocols are critical for stone patients.

Performance of a Natural Language Processing Method to Extract Stone Composition From the Electronic Health Record

OBJECTIVES

To demonstrate the utility of a natural language processing (NLP) algorithm for mining kidney stone composition in a large-scale electronic health records (EHR) repository.

METHODS

We developed StoneX, a pattern-matching method for extracting kidney stone composition information from clinical notes. We trained the extraction algorithm on manually annotated text mentions of calcium oxalate monohydrate, calcium oxalate dihydrate, hydroxyapatite, brushite, uric acid, and struvite stones. We employed StoneX to identify patients with kidney stone composition data and mine >125 million notes from our institutional EHR. Analyses performed on the extracted patients included stone type conversions over time, survival analysis from a second stone surgery, and disease associations by stone composition to validate the phenotyping method against known associations.

RESULTS

The NLP algorithm identified 45,235 text mentions corresponding to 11,585 patients. Overall, the system achieved positive predictive value >90% for calcium oxalate monohydrate, calcium oxalate dihydrate, hydroxyapatite, brushite, and struvite; except for uric acid (positive predictive value = 87.5%). Survival analysis from a second stone surgery showed statistically significant differences among stone types (P = .03). Several phenotype associations were found: uric acid-type 2 diabetes (odds ratio, OR = 2.69, 95% confidence intervals, CI = 1.91-3.79), struvite-neurogenic bladder (OR = 12.27, 95% CI = 4.33-34.79), struvite-urinary tract infection (OR = 7.36, 95% CI = 3.01-17.99), hydroxyapatite-pulmonary collapse (OR = 3.67, 95% CI = 2.10-6.42), hydroxyapatite-neurogenic bladder (OR = 5.23, 95% CI = 2.05-13.36), brushite-calcium metabolism disorder (OR = 4.59, 95% CI = 2.14-9.81), and brushite-hypercalcemia (OR = 4.09, 95% CI = 1.90-8.80).

CONCLUSION

NLP extraction of kidney stone composition from large-scale EHRs is feasible with high precision, enabling high-throughput epidemiological studies of kidney stone disease. These tools will enable high fidelity kidney stone research from the EHR.

Clinical and demographic predictors of repeat stone surgery

OBJECTIVE

To identify the clinical and demographic predictors of repeat stone surgery.

MATERIALS AND METHODS

We retrospectively analysed 1496 consecutive patients, aged > 18 years, who underwent stone surgery at our institution in the period from January 2009 to May 2017 and who had at least 12 months of postoperative follow-up. We defined surgical recurrence as repeat surgery on the same renal unit or on the opposite renal unit if the original imaging did not demonstrate significant stones on that side. Characteristics associated with the risk of surgical recurrence in univariate Cox regression analysis were entered into a multivariate model.

RESULTS

Most patients underwent ureteroscopy and laser lithotripsy (83.0%). Approximately 60% of the patients had a personal history of stone disease and 50% were obese. Over a mean (median; interquartile range) follow-up of 4.1  (3.9; 2.4-5.9) years, 24.5% of patients had surgical recurrence, with 82% of repeat surgeries performed for symptomatic nephrolithiasis. The factors associated with increased risk of surgical recurrence in the multivariate model were: age <60 years, female gender, malabsorptive gastrointestinal disease, diabetes, recurrent urinary tract infections, personal history of nephrolithiasis, renal stones and bilateral nephrolithiasis. The hazard ratios for these variables ranged within an interval of <0.5 (from 1.30 to 1.71).

CONCLUSION

We identified eight demographic and clinical factors associated with increased risk of repeat renal stone surgery. These factors could be combined as a numerical count that allows stratification of patients into low-, intermediate- and high-risk subgroups.

Symptomatic and Radiographic Manifestations of Kidney Stone Recurrence and Their Prediction by Risk Factors: A Prospective Cohort Study

BACKGROUND

Meaningful interpretation of changes in radiographic kidney stone burden requires understanding how radiographic recurrence relates to symptomatic recurrence and how established risk factors predict these different manifestations of recurrence.

METHODS

We recruited first-time symptomatic stone formers from the general community in Minnesota and Florida. Baseline and 5-year follow-up study visits included computed tomography scans, surveys, and medical record review. We noted symptomatic recurrence detected by clinical care (through chart review) or self-report, and radiographic recurrence of any new stone, stone growth, or stone passage (comparing baseline and follow-up scans). To assess the prediction of different manifestations of recurrence, we used the Recurrence of Kidney Stone (ROKS) score, which sums multiple baseline risk factors.

RESULTS

Among 175 stone formers, 19% had symptomatic recurrence detected by clinical care and 25% detected by self-report; radiographic recurrence manifested as a new stone in 35%, stone growth in 24%, and stone passage in 27%. Among those with a baseline asymptomatic stone (54%), at 5 years, 51% had radiographic evidence of stone passage (accompanied by symptoms in only 52%). Imaging evidence of a new stone or stone passage more strongly associated with symptomatic recurrence detected by clinical care than by self-report. The ROKS score weakly predicted one manifestation-symptomatic recurrence resulting in clinical care (c-statistic, 0.63; 95% confidence interval, 0.52 to 0.73)-but strongly predicted any manifestation of symptomatic or radiographic recurrence (5-year rate, 67%; c-statistic, 0.79; 95% confidence interval, 0.72 to 0.86).

CONCLUSIONS

Recurrence after the first stone episode is both more common and more predictable when all manifestations of recurrence (symptomatic and radiographic) are considered.

External Validation of the Recurrence of Kidney Stone Nomogram in a Surgical Cohort

Objective: To assess the performance of recurrence of kidney stone (ROKS) nomogram in identifying first-time stone formers who will require future stone procedures. Materials and Methods: From January 2009 to February 2016, 2287 patients underwent surgical treatment for nephrolithiasis at our institution and 498 of them were eligible for this study. We defined recurrence as repeat surgery for symptomatic nephrolithiasis. We analyzed the performance of the nomogram with respect to discrimination, calibration, and the clinical net benefit. We also examined the performance of each individual variable from the nomogram. Results: Over a median follow-up of 4.8 years (mean 4.6, IQR 3.1-6.1), 88 patients (17.7%) had recurrent nephrolithiasis requiring surgical treatment. The ROKS nomogram demonstrated moderate discriminative ability (AUC 0.655 for 2 years and 0.605 for 5 years). Calibration of the ROKS nomogram-based predictions was poor and net clinical benefit was minimal. Three of 11 predictors from the nomogram were statistically significantly associated with the risk of repeat surgery, with two of them representing similar clinical scenarios, namely symptomatic and nonsymptomatic renal stones. Conclusion: ROKS nomogram demonstrated limited discrimination and calibration in predicting the risk of repeat surgery for symptomatic nephrolithiasis in our cohort of first-time stone formers. This may be caused by the differences between stone patients who do and do not require surgery and suggests the need for development of more precise prediction instruments.

A Retrospective Study of Kidney Stone Recurrence in Adults

Background

Nephrolithiasis or kidney stone disease (KSD) is a common disorder worldwide. Despite the availability of a variety of effective management strategies, KSD recurrence remains a problem. In the present study, we investigated the KSD recurrence after the treatment of the first stone episode.

Methods

Medical records of all patients who had KDS treated in our department from January 2012 to January 2016 were retrospectively reviewed. A total of 146 patients who had KDS recurrence were identified. The demographic information, biochemical data, treatment methods, report of hydronephrosis severity and stone chemical compositions were collected and analyzed.

Results

We reported that: 1) Sixty four (43.8%) out of 146 patients with stone recurrence were overweight or obese; 2) Of all 146 patients with stone recurrence, 86 (58.9%) had hyperlipidemia, 77 (52.4%) had hyperuricemia and 64 (43.8%) had hyperglycemia; 3) Mini-invasive methods were mostly used for the treatment of the first stone episode; 4) The most chief complaint differed during the first episode and recurrence; 5) The number of patients who had grades 3 and 4 hydronephrosis was significantly lower during recurrence compared with that in the first stone episode; 6) Seventy nine (54.1%) patients with recurrence had stone of calcium oxalate.

Conclusions

Majority of patients with KSD recurrence have overweight/obesity, hyperlipidemia, hyperuricemia and hyperglycemia, indicating a role of metabolic disorders in stone recurrence. Mini-invasive methods are the mainstay for the management of the first stone episode. The degree of hydronephrosis is significantly reduced during stone recurrence, possibly due to increased awareness of the disease and thereafter the change of lifestyle in patients. Over half of recurrent stones are of calcium oxalate.

Defining a clinically significant struvite stone: a non-randomized retrospective study

OBJECTIVE

To study the association between a stone's struvite content and clinical outcomes and to determine a clinically significant cutoff for defining struvite stones.

MATERIALS AND METHODS

This was a retrospective study of all patients who underwent ureteroscopy or PCNL at our institution between 2012 and 2017 and had any component of struvite in the stone analysis. Patients were divided into four groups based on percent struvite content: A (1-25%), B (26-50%), C (51-75%), and D (76-100%). Bacterial characteristics were compared between groups. Univariate and multivariate analyses were performed to evaluate the association between struvite content and postoperative SIRS. Log-rank test was used to compare between the four groups' recurrence rates.

RESULTS

A total of 123 patients were included in the study. Positive preoperative urine culture was found in 31%, 81%, 87%, and 90% of patients from group A, B, C, and D, respectively. E. Coli was the most common pathogen in group A (54%), while Proteus was the most common pathogen in groups C (53%) and D (47%). Enterococci isolation rates remained similar between groups A-D, ranging from 23 to 33%. Postoperative SIRS occurred in 2.4%, 21.3%, 26.7%and 47.4% of the patients from groups A, B, C, and D, respectively, and was associated with struvite content and age on multivariate analysis. Increasing struvite content was associated with higher 2-year recurrence rate.

CONCLUSIONS

Higher struvite content is associated with a higher frequency of traditional urea splitting bacteria in urine culture, higher risk for postoperative SIRS, and higher recurrence rate. Struvite content greater than 25% can be used to define a clinically significant struvite stone.

Leave no stone unturned: defining recurrence in kidney stone formers

PURPOSE OF REVIEW

Established guidelines provide recommendations on the management of kidney stones to prevent recurrence. However, clear and clinically useful terminology for recurrence of kidney stones is needed. This review describes the various manifestations of kidney stone recurrence and the reported rates of kidney stone recurrence in various clinical settings.

RECENT FINDINGS

Kidney stone recurrence has a wide range of symptomatic and radiographic presentations. Symptomatic recurrence may include characteristic symptoms of stone passage via the ureter (renal colic and gross hematuria). This may be self-managed or result in clinical care, with or without confirmation of an obstructing stone on imaging. Radiographic recurrence has been variably defined as new stone formation, stone growth, or stone disappearance (from passage with or without symptoms). Studies have used inconsistent definitions of recurrence, and recurrence rates vary substantially. Stone free rates and residual stone fragment size after surgical interventions are useful predictors of symptomatic recurrence.

SUMMARY

The recurrence rate of kidney stones has been assessed in stone formers from sub-specialty clinics, the general community, and clinical trials. The definition of recurrence is quite heterogenous between studies, but the rate of recurrence generally increases as more manifestations are included in the definition.

Predictors of Symptomatic Kidney Stone Recurrence After the First and Subsequent Episodes

OBJECTIVE

To predict symptomatic recurrence among community stone formers with one or more previous stone episodes.

PATIENTS AND METHODS

A random sample of incident symptomatic kidney stone formers in Olmsted County, Minnesota, was followed for all symptomatic stone episodes resulting in clinical care from January 1, 1984, through January 31, 2017. Clinical and radiographic characteristics at each stone episode predictive of subsequent episodes were identified.

RESULTS

There were 3364 incident kidney stone formers with 4951 episodes. The stone recurrence rates per 100 person-years were 3.4 (95% CI, 3.2-3.7) after the first episode, 7.1 (95% CI, 6.4-7.9) after the second episode, 12.1 (95% CI, 10.3-13.9) after the third episode, and 17.6 (95% CI, 15.1-20.0) after the fourth or higher episode (P<.001 for trend). A parsimonious model identified the following independent risk factors for recurrence: younger age; male sex; higher body mass index; family history of stones; pregnancy; incident asymptomatic stone on imaging before the first episode; suspected stone episode before the first episode; history of a brushite, struvite, or uric acid stone; no history of calcium oxalate monohydrate stone; kidney pelvic or lower pole stone on imaging; no ureterovesical junction stone on imaging; number of kidney stones on imaging; and diameter of the largest kidney stone on imaging. The model had a C-index corrected for optimism of 0.681 and was used to develop a prediction tool. The risk of recurrence in 5 years ranged from 0.9% to 94%, depending on risk factors, number of past episodes, and years since the last episode.

CONCLUSION

The revised Recurrence Of Kidney Stone tool predicts the risk of symptomatic recurrence by using readily available clinical characteristics of stone formers.

Protective potential of Angelica sinensis polysaccharide extract against ethylene glycol-induced calcium oxalate urolithiasis

Purpose: To evaluate a Angelica sinensis polysaccharide aqueous extract as a preventive agent in experimentally induced urolithiasis using in- vitro and vivo models.

Material and methods:Angelica sinensis polysaccharide was investigated in vitro to determine its antilithiatic effects on the formation and morphology of calcium oxalate (CaOx) crystals and was analyzed in vivo to determine its ability to prevent CaOx urolithiasis in rats subjected to ethylene glycol-induced urolithiasis. Potassium citrate administration was used in the positive control group. The urolithiasis-related biochemical parameters were evaluated in the rats urine, serum and kidney homogenates. Kidney sections were subjected to histopathological and immunohistochemical analyses, and urolithiasis-related phospho-c-Jun NH2-terminal protein kinase and kidney injury molecule-1proteins were evaluated by Western blot analyses.

Results:Angelica sinensis polysaccharide exhibited concentration-dependent inhibition of CaOx crystal formation. The in vitro assay revealed significant inhibition of crystal formation (6.99 ± 1.07) in the group treated with 4.0 mg/mL Angelica sinensis polysaccharide extract compared with the control group (58.38 ± 5.63; p < .05). In vivo, after treatment with ethylene glycol for 28 days, urinary oxidative stress, oxalate, creatinine, urea and urolithiasis-related protein were significantly increased (p < .05), except for serum oxidative stress (p > .05). The rats administered the extract of Angelica sinensis polysaccharide showed significantly decreased pathological change and CaOx deposition (p < .05) compared with the urolithiatic rats. Significantly reduced levels of urinary oxidative stress, oxalate, creatinine, urea and urolithiasis-related protein were observed in the Angelica sinensis polysaccharide treatment groups (p < .05) compared with the nephrolithic rats.

Conclusion: The results presented here suggest that Angelica sinensis polysaccharide has the potential to inhibit CaOx crystallization in vitro and may present anti-urolithiatic effects in vivo.

Empiric therapy for kidney stones

Careful phenotyping of patients to classify those with kidney stones has a long and important history in revealing the chemical basis for stone formation. Advances in our genetic understanding of kidney stones will lead to incredible insights regarding the pathophysiology of this common disorder. At this time, both evaluation of urine chemistry and genotyping of patients are extremely useful in the setting of a university and research-based kidney stone clinic. For much of the world, in a more clinically focused setting, these techniques are neither available nor absolutely necessary. Careful implementation of an empiric prescription based on stone composition would have an important effect to reduce stone recurrence in the world's many stone formers. Increased fluid intake, generic dietary manipulations, and prescription of potassium citrate and thiazides are all appropriate empiric therapies for people with calcium and uric acid kidney stones.

Living kidney donation from people at risk of nephrolithiasis, with a focus on the genetic forms

Deciding whether to accept a donor with nephrolithiasis is a multifaceted task because of the challenge of finding enough suitable donors while at the same time ensuring the safety of both donors and recipients. Until not long ago, donors with a history of renal stones or with stones emerging during screening on imaging were not considered ideal, but recent guidelines have adopted less stringent criteria for potential donors at risk of stones. This review goes through the problems that need to be approached to arrive at a wise clinical decision, balancing the safety of donors and recipients with the need to expand the organ pool. The risk of declining renal function and worsening stone formation is examined. Documents (consensus statements, guidelines, etc.) on this issue released by the most important medical societies and organizations are discussed and compared. Specific problems of living kidney donation associated with certain systemic (chronic hypercalcemia due to CYP24A1 gene mutations, primary hyperoxaluria, APRT deficiency) and renal (medullary sponge kidney, cystinuria, distal renal tubular acidosis, Dent's disease, Bartter syndrome, familial hypomagnesemia with hypercalciuria and nephrocalcinosis) Mendelian disorders that cause nephrolithiasis are also addressed.

Defining metabolic activity of nephrolithiasis - Appropriate evaluation and follow-up of stone formers

Considering the variation in metabolic evaluation and medical management of kidney stone disease, this consensus review was created to discuss the metabolic activity of nephrolithiasis, define the difference between single and recurrent stone formers, and develop a schema for metabolic and radiologic follow-up. A systematic review of the literature was performed to identify studies of metabolic evaluation and follow-up of patients with nephrolithiasis. Both single and recurrent stone formers share many similarities in metabolic profiles. The study group determined that based on an assessment of risk for stone recurrence and metabolic activity, single and recurrent stone formers should be evaluated comprehensively, including two 24 h urine studies on a random diet. Targeted medication and dietary recommendations are effective for many patients in reducing the risk of stone recurrence. Follow-up of those with stone disease should be obtained depending on the level of metabolic activity of the patient, the risk of chronic kidney disease and the risk of osteoporosis/osteopenia. A standard scheme includes a baseline metabolic profile, a repeat study 3-6 months after initiation of treatment, and then yearly when stable, with abdominal imaging obtained every 1-2 years.

A User-Friendly Application to Automate CT Renal Stone Measurement

INTRODUCTION

CT is the gold standard for visualizing renal and ureteral calculi. CT three-dimensional reformatting allows for automatic, accurate, and reliable measurement of stone size, volume, density, and location. In this study, we aimed to develop and test a software platform capable of calculating a battery of clinically important urinary stone parameters at the point-of-care (POC).

METHODS

The syngo Calcium Scoring (Siemens Corporation) algorithm was modified to identify calcium-based stones using an attenuation threshold (250 HU) within a region of interest. Information automatically obtained after reconstruction included voxel sum and calculated volume, maximum diameter, largest diameter in the x, y, and z planes, cumulative diameter, distribution of attenuation in HU, and position relative to the skin for calculation of the skin-to-stone distance (SSD). This algorithm was packaged into a stand-alone application (MATLAB 9.1). From April 2017 to May 2017, all patients undergoing a noncontrast CT of the abdomen or the abdomen and pelvis at the Johns Hopkins Hospital were eligible for inclusion in this validation cohort.

RESULTS

A total of 55 index renal stones were included. The mean volume calculated by voxel sum was 216.53 mm³ (standard deviation [SD] ±616.19, range 1.50-4060.13). The mean volume calculated using the Ackermann's formula and for a sphere was 232.96 mm³ (SD ± 702.65, range 1.24-4074.04) and 1214.63 mm³ (SD ± 4233.41, range 1.77-25,246.40), respectively. The mean largest diameter in any one direction was 6.95 mm (SD ± 7.31, range 1.50-36.40). The maximum density of the stones ranged from 164 to 1725 HU. The mean SSD at the shortest possible point was 14.19 cm (SD ± 6.13, range 6.67-31.28).

CONCLUSIONS

We developed a stand-alone platform with a simple easy-to-use interface, which will allow any user the ability to calculate a battery of clinically important urinary stone parameters from CT imaging at the POC. This program is now freely available online.

24-h urine metabolic profile: is it necessary in all kidney stone formers?

PURPOSE

A 24-h urine metabolic profile (24-UMP) is an integral part of nephrolithiasis work-up. We aimed to explore whether it can be waived under certain circumstances.

MATERIALS AND METHODS

We reviewed our prospective registry database of patients seen at our outpatient clinic for nephrolithiasis between the years 2010 and 2017. Data included: gender, age at first stone, body mass index (BMI), self-reported comorbidities and family history of nephrolithiasis. A 24-UMP was obtained from each patient under random diet. The following were recorded: urine volume, urinary levels of sodium, calcium, uric acid, oxalate and citrate. Presence of at least one comorbidity (i.e., hypertension/diabetes/hyperlipidemia) was defined as "associated comorbidities" (AC). Their absence was defined as "no comorbidities" (NC). Subjects were divided into two subgroups: first-time and recurrent stone formers, which were further divided into two subgroups: 1st + AC; 1st + NC; recurrent + AC; recurrent + NC. 24-UMPs have been compared between the four groups.

RESULTS

Four hundred and fifty-seven patients were included in the study. In the AC groups, patients demonstrated higher BMI levels (p = 0.001), and were statistically significantly obese (BMI > 30, p = 0.001) and older at first stone event (p = 0.001). First formers, either with AC or NC were more likely to have low urine volume (LUV) compared with recurrent formers (72.5 vs. 59.5%, p = 0.005). In the remaining metabolic abnormalities, no such differences were observed.

CONCLUSIONS

First-time stone formers, either with or without AC are likely to demonstrate LUV as their primary metabolic abnormality in 24-UMP. Therefore, 24-UMP may be postponed until recurrent stone event.

Incidence and characteristics of kidney stones in patients with horseshoe kidney: A systematic review and meta-analysis

Introduction

The horseshoe kidney (HSK) is the most common type of renal fusion anomaly. The incidence and characteristics of kidney stones in patients with HSK are not well studied. The aim of this meta-analysis was to evaluate the incidence and types of kidney stones in patients with HSK.

Methods

A systematic literature search was performed using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from the databases' inception through November 2016. Studies assessing the incidence and types of kidney stones in patients with HSK were included. We applied a random-effects model to estimate the incidence of kidney stones. The study protocol was registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42016052037).

Results

A total of 14 observational studies with 943 patients (522 adults and 421 pediatric) with HSK were enrolled. The estimated pooled incidence of kidney stones was 36% (95% confidence interval [CI], 15%-59%) in adults with the HSK. Kidney stones were less common in pediatric patients with HSK with an estimated pooled incidence of 3% (95% CI, 2%-5%). The mean age of adult stone formers with HSK was 44.9 ± 6.2 years, and 75% were males. Within reported studies, 89.2% of kidney stones were calcium-based stones (64.2% calcium oxalate [CaOx], 18.8% calcium phosphate [CaP], and 6.2% mixed CaOx/CaP), followed by struvite stones (4.2%), uric acid stones (3.8%), and others (2.8%).

Conclusions

Kidney stones are very common in adult patients with HSK with an estimated incidence of 36%. Calcium-based stones are the most prevalent kidney stones in adults with HSKs. These findings may impact the prevention and clinical management of kidney stones in patients with HSK.

Ultrasound-guided percutaneous nephrolithotomy for the treatment in patients with kidney stones

BACKGROUND

In this study, we aimed to explore the effect of ultrasound-guided percutaneous nephrolithotomy (UGPN) for the treatment in patients with kidney stones (KS).

METHODS

We randomly assigned 86 patients with KS to a UGPN group or a control group, each group comprising 43 patients. Patients from the UGPN group underwent UGPN whereas those from control group underwent fluoroscopic-guided percutaneous nephrolithotomy (FGPN). The primary outcome included the stone-free rate. Secondary outcomes included complication rates, operative time, and length of hospitalization.

RESULTS

UGPN did not show better efficacy than the FGPN procedure in decreasing stone-free rate (UGPN group 79.1% vs control group 69.8%, P = .45), operative time (UGPN group 108.4 ± 31.7 minute vs control group 113.2 ± 34.5 minute, P = .50), and length of hospitalization (UGPN group 2.7 ± 1.3 days vs control group 3.1 ± 1.5 days, P = .19). Additionally, no complications, except fever (UGPN group 4.7% vs control group 9.3%, P = .41) and hemoglobin slightly reduced (UGPN group 7.0% vs control group 11.6%, P = .46) were noted in patients from both groups in this study.

CONCLUSIONS

To summarize, we demonstrated that both UGPN and FGPN techniques showed similar efficacy and complications when used for the management of KS.

Medical and dietary interventions for preventing recurrent urinary stones in children

BACKGROUND

Nephrolithiasis, or urinary stone disease, in children causes significant morbidity, and is increasing in prevalence in the North American population. Therefore, medical and dietary interventions (MDI) for recurrent urinary stones in children are poised to gain increasing importance in the clinical armamentarium.

OBJECTIVES

To assess the effects of medical and dietary interventions (MDI) for the prevention of idiopathic urinary stones in children aged from one to 18 years.

SEARCH METHODS

We searched multiple databases using search terms relevant to this review, including studies identified from the Cochrane Central Register of Controlled Trials (CENTRAL, 2017, Issue 1), MEDLINE OvidSP (1946 to 14 February 2017), Embase OvidSP (1980 to 14 February 2017), International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov. Additionally, we handsearched renal-related journals and the proceedings of major renal conferences, and reviewed weekly current awareness alerts for selected renal journals. The date of the last search was 14 February 2017. There were no language restrictions.

SELECTION CRITERIA

Randomized controlled trials of at least one year of MDI versus control for prevention of recurrent idiopathic (non-syndromic) nephrolithiasis in children.

DATA COLLECTION AND ANALYSIS

We used standard methodologic procedures expected by Cochrane. Titles and abstracts were identified by search criteria and then screened for relevance, and then data extraction and risk of bias assessment were carried out. We assessed the quality of evidence using GRADE.

MAIN RESULTS

The search identified one study of 125 children (72 boys and 53 girls) with calcium-containing idiopathic nephrolithiasis and normal renal morphology following initial treatment with shockwave lithotripsy (SWL). Patients were randomized to oral potassium citrate 1 mEq/kg per day for 12 months versus no specific medication or preventive measure with results reported for a total of 96 patients (48 per group). This included children who were stone-free (n = 52) or had residual stone fragments (n = 44) following SWL. Primary outcomes:Medical therapy may lower rates of stone recurrence with a risk ratio (RR) of 0.19 (95% confidence interval (CI) 0.06 to 0.60; low quality evidence). This corresponds to 270 fewer stone recurrences per 1000 (133 fewer to 313 fewer) children. We downgraded the quality of evidence by two levels for very serious study limitations related to unclear allocation concealment (selection bias) and a high risk of performance, detection and attrition bias. While the data for adverse events were incomplete, they reported that six of 48 (12.5%) children receiving potassium citrate left the trial because of adverse effects. This corresponds to a RR of 13.0 (95% CI 0.75 to 224.53; very low quality evidence); an absolute effect size estimate could not be generated. We downgraded the quality of evidence for study limitations and imprecision.We found no information on retreatment rates.

SECONDARY OUTCOMES

We found no evidence on serum electrolytes, 24-hour urine collection parameters or time to new stone formation.We were unable to perform any preplanned secondary analyses.

AUTHORS' CONCLUSIONS

Oral potassium citrate supplementation may reduce recurrent calcium urinary stone formation in children following SWL; however, our confidence in this finding is limited. A substantial number of children stopped the medication due to adverse events. There is no trial evidence on retreatment rates. There is a critical need for additional well-designed trials in children with nephrolithiasis.

Effectiveness of Treatment Modalities on Kidney Stone Recurrence

Nephrolithiasis is highly prevalent across all demographic groups in the Western world and beyond, and its incidence rates are rising. In addition to the morbidity of the acute event, stone disease often becomes a lifelong problem that requires preventative therapy to diminish ongoing morbidity. Across the majority of stone types, increased fluid intake and targeted dietary modifications are mainstays of therapy. Specific dietary interventions associated with reduced calcium stone risk include adequate dietary calcium intake and restriction of sodium, protein, and oxalate intake, among others. Pharmaceutical therapy may be required if lifestyle changes are insufficient to minimize risk of stone recurrence, and must be targeted to the specific metabolic abnormalities portending risk for a given patient. Therapeutic options for idiopathic calcium stone disease include thiazides, citrate salts, and uric acid-lowering agents. Alkali salts are also the treatment of choice for uric acid stone disease. Management of struvite stone disease is largely surgical, but acetohydroxamic acid is a proven second line therapy. Cystinuria requires lifestyle modifications and may call for thiol-binding agents. Significant heterogeneity of the clinical population with stone disease has previously limited opportunities for large randomized controlled trials. However, as clinical phenotypes and genotypes are increasingly clarified, there are mounting opportunities for targeted randomized controlled trials in stone prevention. In the meantime, the currently available evidence for both lifestyle and pharmacologic interventions is reviewed herein.

Epidemiology and economics of nephrolithiasis

Nephrolithiasis is a disease common in both the Western and non-Western world. Several population based studies have demonstrated a rising prevalence and incidence of the disease over the last several decades. Recurrence occurs frequently after an initial stone event. The influence of diet on the risk of nephrolithiasis is important, particularly dietary calcium and fluid intake. An increasing intake of dietary calcium and fluid are consistently associated with a reduced risk of incident nephrolithiasis in both men and women. Increasing evidence suggests that nephrolithiasis is associated with systemic diseases like obesity, diabetes, and cardiovascular disease. Nephrolithiasis places a significant burden on the health care system, which is likely to increase with time.

Optimization of urinary dipstick pH: Are multiple dipstick pH readings reliably comparable to commercial 24-hour urinary pH?

Purpose

Accurate measurement of pH is necessary to guide medical management of nephrolithiasis. Urinary dipsticks offer a convenient method to measure pH, but prior studies have only assessed the accuracy of a single, spot dipstick. Given the known diurnal variation in pH, a single dipstick pH is unlikely to reflect the average daily urinary pH. Our goal was to determine whether multiple dipstick pH readings would be reliably comparable to pH from a 24-hour urine analysis.

Materials and Methods

Kidney stone patients undergoing a 24-hour urine collection were enrolled and took images of dipsticks from their first 3 voids concurrently with the 24-hour collection. Images were sent to and read by a study investigator. The individual and mean pH from the dipsticks were compared to the 24-hour urine pH and considered to be accurate if the dipstick readings were within 0.5 of the 24-hour urine pH. The Bland-Altman test of agreement was used to further compare dipstick pH relative to 24-hour urine pH.

Results

Fifty-nine percent of patients had mean urinary pH values within 0.5 pH units of their 24-hour urine pH. Bland-Altman analysis showed a mean difference between dipstick pH and 24-hour urine pH of -0.22, with an upper limit of agreement of 1.02 (95% confidence interval [CI], 0.45–1.59) and a lower limit of agreement of -1.47 (95% CI, -2.04 to -0.90).

Conclusions

We concluded that urinary dipstick based pH measurement lacks the precision required to guide medical management of nephrolithiasis and physicians should use 24-hour urine analysis to base their metabolic therapy.

Incidence of kidney stones in kidney transplant recipients: A systematic review and meta-analysis

AIM

To evaluate the incidence and characteristics of kidney stones in kidney transplant recipients.

METHODS

A literature search was performed using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from the inception of the databases through March 2016. Studies assessing the incidence of kidney stones in kidney transplant recipients were included. We applied a random-effects model to estimate the incidence of kidney stones.

RESULTS

Twenty one studies with 64416 kidney transplant patients were included in the analyses to assess the incidence of kidney stones after kidney transplantation. The estimated incidence of kidney stones was 1.0% (95%CI: 0.6%-1.4%). The mean duration to diagnosis of kidney stones after kidney transplantation was 28 ± 22 mo. The mean age of patients with kidney stones was 42 ± 7 years. Within reported studies, approximately 50% of kidney transplant recipients with kidney stones were males. 67% of kidney stones were calcium-based stones (30% mixed CaOx/CaP, 27%CaOx and 10%CaP), followed by struvite stones (20%) and uric acid stones (13%).

CONCLUSION

The estimated incidence of kidney stones in patients after kidney transplantation is 1.0%. Although calcium based stones are the most common kidney stones after transplantation, struvite stones (also known as “infection stones”) are not uncommon in kidney transplant recipients. These findings may impact the prevention and clinical management of kidney stones after kidney transplantation.

Diagnosis and Management of Nephrolithiasis

Nephrolithiasis is a common affliction, affecting approximately 10% of adults. Potentially presenting with acute abdominal or flank pain, nausea, or emesis, it may pose as a general surgical condition. Therefore, recognition, diagnosis, and management concerns are pertinent to the general surgeon. Furthermore, the risk of nephrolithiasis is increased in common general surgical conditions, including inflammatory bowel disease, hyperparathyroidism, and short gut. Nephrolithiasis may be induced as a result of general surgical interventions, including gastric bypass and bowel resection with ileostomy. An understanding of this common disease will improve coordination of patient care between urologists and general surgeons.

Endoscopic Evidence That Randall's Plaque is Associated with Surface Erosion of the Renal Papilla

OBJECTIVE

This study was conducted to assess the reliability and precision of an endoscopic grading scale to identify renal papillary abnormalities across a spectrum of equipment, locations, graders, and patients.

MATERIALS AND METHODS

Intra- and interobserver reliability of the papillary grading system was assessed using weighted kappa scoring among 4 graders reviewing a single renal papilla from 50 separate patients on 2 occasions. Grading was then applied to a cohort of patients undergoing endoscopic stone removal procedures at two centers. Patient factors were compared with papillary scores on the level of the papilla, kidney, and patient.

RESULTS

Graders achieved substantial (kappa >0.6) intra- and inter-rater reliability in scored domains of ductal plugging, surface pitting, and loss of contour. Agreement for Randall's Plaque (RP) was moderate. Papillary scoring was then performed for 76 patients (89 kidneys, 533 papillae). A significant association was discovered between pitting and RP that held both within and across institutions. A general linear model was then created to further assess this association and it was found that RP score was a highly significant independent correlate of pitting score (F = 7.1; p < 0.001). Mean pitting scores increased smoothly and progressively with increasing RP scores. Sums of the scored domains were then calculated as a reflection of gross papillary abnormality. When analyzed in this way, a history of stone recurrence and shockwave lithotripsy were strongly predictive of higher sums.

CONCLUSIONS

Renal papillary pathology can be reliably assessed between different providers using a newly described endoscopic grading scale. Application of this scale to stone-forming patients suggests that the degree of RP appreciated in the papilla is strongly associated with the presence of pitting. It also suggests that patients with a history of recurrent stones and lithotripsy have greater burdens of gross papillary disease.

Calcium urolithiasis course in young stone formers is influenced by the strength of family history: results from a retrospective study

The role of the strength of family history of stones (FHS), i.e., degree of relatives with the disease, on the course of calcium urolithiasis (CU) is not fully understood, particularly in young patients where genetic background has the greatest influence on disease expression. Thus, with a retrospective cross-sectional design, we examined baseline clinical parameters and urinary chemistries of 369 subjects (196 M) with CU and 96 controls (41 M) aged between 15 and 25 at the time of the first visit at our stone clinic. Subjects with metabolic syndrome traits, known causes of CU or CU onset before the age of 15 were excluded. Clinical and metabolic parameters were compared among stone formers (SF) and controls, stratified by gender, the presence and type of FHS determined through the kinship coefficient of relatives with stones. No significant differences in clinical course were found between SF with and without FHS, except for the presence of bilateral stones (OR 2.01, 95% CI 1.20-3.39, p < 0.01). A significant age-, sex- and disease duration-adjusted trend for a higher number of colics (p for trend = 0.001), number of stones (p for trend = 0.002), stone rate (p for trend = 0.003) and the presence of retained stones (OR 1.60, 95% CI 1.14-2.21, p = 0.006) was detected with increasing FHS strength. Urinary chemistries were unaffected by FHS in both SF and controls, except for a higher calcium excretion in females with FHS (p < 0.05). The type of FHS, thus, significantly influences the clinical course of CU in young SF, mainly irrespective of urinary factors.

Kidney Function After the First Kidney Stone Event

OBJECTIVE

To determine whether there is a persistent decline in kidney function after the first kidney stone event.

PATIENT AND METHODS

Incident symptomatic stone formers and age- and sex-matched controls underwent 2 study visits 90 days apart to assess kidney function, complete a survey, and have their medical records reviewed. Kidney function was compared between stone formers and controls adjusting for clinical, blood, and urine risk factors.

RESULTS

There were 384 stone formers and 457 controls. At visit 1, a median of 104 days after the stone event, stone formers compared with controls had similar serum creatinine (0.86 vs 0.84 mg/dL; P=.23), higher serum cystatin C (0.83 vs 0.72 mg/L; P<.001), higher urine protein (34.2 vs 19.7 mg/24 h; P<.001) levels, and were more likely to have albuminuria (24 h urine albumin >30 mg: 5.4% vs 2.2%; P=.02). Findings were similar after adjustment for risk factors and at visit 2, a median of 92 days after visit 1. In the 173 stone formers with serum creatinine levels from care before study participation, the mean serum creatinine level was 0.84 mg/dL before the stone event, increased to 0.97 mg/dL (P<.001) at the stone event, but returned to 0.85 mg/dL (P=.38) after the stone event (visit 1).

CONCLUSIONS

Incident symptomatic stone formers have a rise in serum creatinine levels that resolves. However, stone formers have sustained higher cystatin C levels and proteinuria that may affect long-term risk of chronic kidney disease.

Metabolic diagnosis and medical prevention of calcium nephrolithiasis and its systemic manifestations: a consensus statement

BACKGROUND

Recently published guidelines on the medical management of renal stone disease did not address relevant topics in the field of idiopathic calcium nephrolithiasis, which are important also for clinical research.

DESIGN

A steering committee identified 27 questions, which were proposed to a faculty of 44 experts in nephrolithiasis and allied fields. A systematic review of the literature was conducted and 5216 potentially relevant articles were selected; from these, 407 articles were deemed to provide useful scientific information. The Faculty, divided into working groups, analysed the relevant literature. Preliminary statements developed by each group were exhaustively discussed in plenary sessions and approved.

RESULTS

Statements were developed to inform clinicians on the identification of secondary forms of calcium nephrolithiasis and systemic complications; on the definition of idiopathic calcium nephrolithiasis; on the use of urinary tests of crystallization and of surgical observations during stone treatment in the management of these patients; on the identification of patients warranting preventive measures; on the role of fluid and nutritional measures and of drugs to prevent recurrent episodes of stones; and finally, on the cooperation between the urologist and nephrologist in the renal stone patients.

CONCLUSIONS

This document has addressed idiopathic calcium nephrolithiasis from the perspective of a disease that can associate with systemic disorders, emphasizing the interplay needed between urologists and nephrologists. It is complementary to the American Urological Association and European Association of Urology guidelines. Future areas for research are identified.

Nephrolithiasis after bariatric surgery: A review of pathophysiologic mechanisms and procedural risk

Obesity alone is a known risk factor for nephrolithiasis, and bariatric surgery has been linked to a higher incidence of post-operative new-onset nephrolithiasis. The mean interval from bariatric surgery to diagnosis of nephrolithiasis, ranges from 1.5 to 3.6 years. The stone risk is greatest for purely malabsorptive procedures, intermediate for Roux-en-Y gastric bypass and lowest for purely restrictive procedures (laparoscopic adjustable gastric banding, laparoscopic sleeve gastrectomy) where it approaches or is reduced below that of non-operative obese controls. A history of nephrolithiasis and increasing age at the time of surgery are both associated with an increased risk of new stone formation post-operatively. The underlying pathophysiologic changes following bariatric surgery include increased colonic absorption of oxalate leading to hyperoxaluria, hypocitraturia and increased urinary calcium oxalate supersaturation, which predispose to stone formation. The majority of incident stones are medically managed, with some requiring interventions in the form of lithotripsy or ureteroscopy.

A new era of Asian urology: a SWOT analysis

Economic prosperity and increasing connectivity have made Asia an emerging centre of growth in health care, including in the field of urology. Large and varied patient populations, the availability of a trained workforce, the use of English as a common communication language, and overall low costs have contributed to this change. Rapid growth of regional urological associations and journals has fuelled the aspirations and abilities of Asian urologists to not only keep abreast of but often lead the change in urological disease management. Asian urology has immense potential to expand in areas in which it currently lags behind, the most important being research. The increasing ability to travel aids in developing networks for collaboration. However, Asian urologists will need to look at sustainable models of engagement and temper the need for short-term results if these opportunities are to reach their maximal potential.

Insights Into Nephrolithiasis From the Nurses' Health Studies

OBJECTIVES

To review the contributions of the Nurses' Health Study (NHS) I and NHS II to understanding the role of dietary factors, beverages, body size, and urinary factors in the development of kidney stones.

METHODS

We conducted a review of kidney stone-related publications of NHS I and NHS II between 1976 and 2016.

RESULTS

Studies using NHS I and NHS II data have demonstrated the importance of many factors in kidney stone formation and were the first to report that higher dietary calcium was associated with a lower risk of incident kidney stones in women. Data from these cohorts were instrumental in emphasizing that nephrolithiasis is a systemic disease and suggesting that a kidney stone or shared risk factors may lead to hypertension, diabetes, and cardiovascular disease.

CONCLUSIONS

Findings from the NHSs have changed the scientific understanding and the clinical practice of stone prevention and have been incorporated into widely consulted textbooks and the American Urological Association Medical Management of Kidney Stones guidelines.

Urinary Stone Disease: Advancing Knowledge, Patient Care, and Population Health

Expanding epidemiologic and physiologic data suggest that urinary stone disease is best conceptualized as a chronic metabolic condition punctuated by symptomatic, preventable stone events. These acute events herald substantial future chronic morbidity, including decreased bone mineral density, cardiovascular disease, and CKD. Urinary stone disease imposes a large and growing public health burden. In the United States, 1 in 11 individuals will experience a urinary stone in their lifetime. Given this high incidence and prevalence, urinary stone disease is one of the most expensive urologic conditions, with health care charges exceeding $10 billion annually. Patient care focuses on management of symptomatic stones rather than prevention; after three decades of innovation, procedural interventions are almost exclusively minimally invasive or noninvasive, and mortality is rare. Despite these advances, the prevalence of stone disease has nearly doubled over the past 15 years, likely secondary to dietary and health trends. The NIDDK recently convened a symposium to assess knowledge and treatment gaps to inform future urinary stone disease research. Reducing the public health burden of urinary stone disease will require key advances in understanding environmental, genetic, and other individual disease determinants; improving secondary prevention; and optimal population health strategies in an increasingly cost-conscious care environment.