Asymptomatic nephrolithiasis detected by ultrasound

Screening for asymptomatic nephrolithiasis in primary hyperparathyroidism patients is warranted

BACKGROUND

We aimed to investigate the prevalence, characteristics, and management of nephrolithiasis in primary hyperparathyroidism (PHPT) patients.

METHODS

Medical records of patients who underwent parathyroidectomy at a tertiary care hospital in British Columbia from January 2016 to April 2023 were retrospectively reviewed. Demographic data, laboratory results, imaging reports, and urologic consultations were examined. Descriptive statistics and relevant statistical tests, including logistic regressions, were utilized for data analysis.

RESULT

Of the 413 PHPT patients included in the study population, 41.9% harbored renal stones, and nearly half (48.6%) required urological interventions. Male sex, elevated preoperative serum ionized calcium (iCa) and 24-h urinary calcium (24 ​h urine Ca) levels were independent risk factors for stone formation. Additionally, male sex, younger age, and lower preoperative serum 25-hydroxyvitamin D (25(OH)D) level were associated with higher odds of requiring urological intervention for stones.

CONCLUSIONS

This study identified significant prevalence of asymptomatic renal calcifications in PHPT patients, with a substantial proportion necessitating urological intervention. These findings emphasize the importance of incorporating screening and treatment of renal stones into the management of PHPT patients.

Clinical characteristics of surgically managed patients with asymptomatic renal stones: Comparison of patients with symptomatic renal stones

PURPOSE

This study aimed to compare the characteristics of asymptomatic and symptomatic nephrolithiasis in patients who underwent surgical treatment for kidney stones.

MATERIALS AND METHODS

Between 2015 and 2019, 245 patients who underwent percutaneous nephrolithotomy or retrograde intrarenal surgery for kidney stones were included. The patients were divided into asymptomatic (n=124) and symptomatic (n=121) groups. All patients underwent blood and urine tests, preoperative non-contrast computed tomography, and postoperative stone composition analysis. We retrospectively analyzed and compared the characteristics of the patients and stones, operation time, stone-free rate, and postoperative complications between the two groups.

RESULTS

In the asymptomatic group, mean body mass index (BMI) was significantly higher (25.7±3.8 kg/m² vs. 24.3±2.8 kg/m², p=0.002) and urine pH was significantly lower (5.6±0.9 vs. 5.9±0.9, p=0.013). The ratio of calcium oxalate dihydrate stones was significantly higher in the symptomatic group (5.3% vs. 15.5%, p=0.023). No significant differences were observed in stone characteristics, postoperative outcomes, or complications. In the multivariate logistic regression analysis for predicting variables for asymptomatic renal stones, BMI (odds ratio [OR], 1.144; 95% confidence interval [CI], 1.038-1.260; p=0.007), and urine pH (OR, 0.608; 95% CI, 0.407-0.910; p=0.016) were independent predictive variables for asymptomatic renal stones.

CONCLUSIONS

This study demonstrated that thorough medical check-ups are needed for the early detection of renal stones in individuals with a high BMI or low urine pH.

[Internal differential diagnoses in acute back pain : An internal perspective on the possible causes of acute back pain]

The majority of patients with acute back pain have no serious underlying disease; however, many internal diseases can be manifested as acute or chronic back pain. Therefore, in the assessment of patients with back pain the clinical history and clinical examination are important in order to detect indications for a possible underlying disease. Particularly red flags that indicate an acute or life-threatening disease should not be missed. In most cases where such red flags, risk factors or clinical indications are not present, no systematic search for internal underlying diseases is necessary. This article summarizes the most relevant differential diagnoses and clinical indications as well as warning symptoms.

Educational Case: Urinary Stones

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, seehttp://journals.sagepub.com/doi/10.1177/2374289517715040. ¹

Natural history of small asymptomatic kidney and residual stones over a long-term follow-up: systematic review over 25 years

OBJECTIVE

To systematically review the natural history of small asymptomatic kidney and residual stones, as the incidental identification of small, asymptomatic renal calculi has risen with increasing use of high-resolution imaging.

MATERIALS AND METHODS

We reviewed the natural history of small asymptomatic kidney and residual stones using the Cochrane and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. We searched MEDLINE, Scopus, EMBASE, EBSCO, Cochrane library and Clinicaltrials.gov using themes of 'asymptomatic', 'nephrolithiasis', 'observation', 'symptoms', 'admission', 'intervention' and similar allied terms for all English language articles from 1996 to 2020 (25 years). Inclusion criteria were studies with ≥50 patients, stones ≤10 mm, and a mean follow-up of ≥24 months. Primary outcomes were occurrence of symptoms, emergency admission, and interventions.

RESULTS

Our literature search returned 2247 results of which 10 papers were included in the final review. Risk of symptomatic episodes ranged from 0% to 59.4%. Meta-analysis did not identify any significant difference in the likelihood of developing symptoms when comparing stones <5 mm to those >5 mm, nor those <10 mm to those >10 mm. Risk of admission varied from 14% to 19% and the risk of intervention from 12% to 35%. Meta-analysis showed a significantly decreased likelihood of intervention for stones <5 vs >5 mm and <10 vs >10 mm. Studies had variable risk of bias due to heterogeneous reporting of outcome measures with significant likelihood that observed differences in results were compatible with chance alone (Symptoms: I² =0%, Cochran's Q = 3.09, P = 0.69; Intervention: I² =0%, Cochran's Q = 1.76, P = 0.88).

CONCLUSIONS

The present systematic review indicates that stone size is not a reliable predictor of symptoms; however, risk of intervention is greater for stones >5mm vs <5 mm and >10 vs <10 mm. This review will inform urologists as they discuss management strategies with patients who have asymptomatic renal stones and offer insight to committees during the development of evidence-based guidelines.

Assessing the Relationship Between Serum Urate and Urolithiasis Using Mendelian Randomization: An Analysis of the UK Biobank

RATIONALE & OBJECTIVE

The association between hyperuricemia and urolithiasis has been previously reported. However, this association is based on observational data, which are prone to residual confounding. The aim of this work was to use Mendelian randomization (MR) to evaluate if this relationship represents a causal effect of hyperuricemia.

STUDY DESIGN

MR analysis using 2 approaches: 2-stage MR and 2-sample MR.

SETTING & PARTICIPANTS

Participants aged 40-69 years from the UK Biobank Resource.

EXPOSURE

Serum urate.

OUTCOME

Urolithiasis.

ANALYTICAL APPROACH

An observational analysis testing for an association between serum urate level and urolithiasis was performed using logistic regression. For MR analyses, serum urate-associated single-nucleotide polymorphisms, identified from genome-wide association data, were used as instrumental variables for serum urate. In the 2-stage MR analysis, a weighted genetic urate score was calculated from the instrumental variables, and a control function estimation model was fit. In the 2-sample MR analysis, multiple-instrument MR via the inverse-variance weighted method was performed.

RESULTS

Individual-level data were available for 359,827 participants, of whom 6,398 (1.8%) reported urolithiasis. In the observational analysis, serum urate was positively associated with urolithiasis in an unadjusted analysis (odds ratio [OR], 1.47 [95% CI, 1.42-1.51]); however, after adjustment for relevant confounders, no association was observed (OR, 1.03 [95% CI, 0.99-1.08]). In the 2-stage MR analysis, no significant causal effect of serum urate level on urolithiasis was observed in the unadjusted (OR, 0.93 [95% CI, 0.81-1.08]) or adjusted (OR, 0.94 [95% CI, 0.80-1.09]) models. In the 2-sample MR analysis, multiple-instrument MR did not indicate a causal effect of serum urate on urolithiasis.

LIMITATIONS

Stone composition and urinalysis data, including urine pH, were not available for this study.

CONCLUSIONS

Our analyses do not support a causal effect of serum urate level on urolithiasis. The association between serum urate level and urolithiasis reported in observational studies is likely due to residual confounding.

Perturbations of the Gut Microbiome and Metabolome in Children with Calcium Oxalate Kidney Stone Disease

BACKGROUND

The relationship between the composition and function of gut microbial communities and early-onset calcium oxalate kidney stone disease is unknown.

METHODS

We conducted a case-control study of 88 individuals aged 4-18 years, which included 44 individuals with kidney stones containing ≥50% calcium oxalate and 44 controls matched for age, sex, and race. Shotgun metagenomic sequencing and untargeted metabolomics were performed on stool samples.

RESULTS

Participants who were kidney stone formers had a significantly less diverse gut microbiome compared with controls. Among bacterial taxa with a prevalence >0.1%, 31 taxa were less abundant among individuals with nephrolithiasis. These included seven taxa that produce butyrate and three taxa that degrade oxalate. The lower abundance of these bacteria was reflected in decreased abundance of the gene encoding butyryl-coA dehydrogenase (P=0.02). The relative abundance of these bacteria was correlated with the levels of 18 fecal metabolites, and levels of these metabolites differed in individuals with kidney stones compared with controls. The oxalate-degrading bacterial taxa identified as decreased in those who were kidney stone formers were components of a larger abundance correlation network that included Eggerthella lenta and several Lactobacillus species. The microbial (α) diversity was associated with age of stone onset, first decreasing and then increasing with age. For the individuals who were stone formers, we found the lowest α diversity among individuals who first formed stones at age 9-14 years, whereas controls displayed no age-related differences in diversity.

CONCLUSIONS

Loss of gut bacteria, particularly loss of those that produce butyrate and degrade oxalate, associates with perturbations of the metabolome that may be upstream determinants of early-onset calcium oxalate kidney stone disease.

Systematic radiologic detection of kidney stones in Canadian children: a new era of asymptomatic stones?

INTRODUCTION

Asymptomatic, or incidental, pediatric kidney stones detected on abdominal imaging pose a clinical challenge as their significance and expected outcome are not well described.

OBJECTIVE

Our primary objective was to estimate the incidence of nephrolithiasis in pediatric patients undergoing abdominal ultrasound (US) or computerized tomography (CT), for all indications, in a pediatric tertiary care hospital. Our secondary objective was to determine the clinical outcome of these radiographically detected stones.

METHODS

All abdominal US or CT radiology reports for patients younger than 18 years between January 1, 2011, and December 31, 2016, were retrieved. Reports were automatically flagged using textual analysis if they contained one of the 32 keywords potentially indicating nephrolithiasis. Flagged reports, as well as 10% of unflagged reports, were reviewed to confirm the radiologist impression of presence or absence of stones. Patient and stone-related clinical data were extracted.

RESULTS

Two thousand four hundred forty-nine (5%) of 53 235 imaging reports cited at least one of the keywords. Manual review of flagged reports identified 498 studies having a radiologist impression of stones (244 unique patients). Stone incidence in children undergoing abdominal imaging more than doubled between 2011 and 2016. Medical record review found that 140 patients (57%) were symptomatic, while the other 104 patients (43%) were asymptomatic. Spontaneous resolution was greater (57% vs 34%) in asymptomatic patients compared to symptomatic patients. Asymptomatic patients were younger with a median age of 0.6 compared to 12.3 years. Asymptomatic and symptomatic stones were followed up for similar lengths of time (2.3 vs 2.0 years, p > 0.05) and had a similar number of follow-up USs (3.9 vs 4.6 studies, p > 0.05).

CONCLUSIONS

The incidence of radiologically identified stones in children undergoing abdominal imaging at our center increased over time. Asymptomatic stones follow a benign course with minimal need for intervention; however, they were detected almost as frequently as symptomatic stones. Asymptomatic stones may represent increased healthcare resource utilization due to similar follow-up compared to symptomatic stones. Further research regarding the optimal imaging intervals and long-term follow-up for asymptomatic stones is warranted.

ALG9 Mutation Carriers Develop Kidney and Liver Cysts

BACKGROUND

Mutations in PKD1 or PKD2 cause typical autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic kidney disease. Dominantly inherited polycystic kidney and liver diseases on the ADPKD spectrum are also caused by mutations in at least six other genes required for protein biogenesis in the endoplasmic reticulum, the loss of which results in defective production of the PKD1 gene product, the membrane protein polycystin-1 (PC1).

METHODS

We used whole-exome sequencing in a cohort of 122 patients with genetically unresolved clinical diagnosis of ADPKD or polycystic liver disease to identify a candidate gene, ALG9, and in vitro cell-based assays of PC1 protein maturation to functionally validate it. For further validation, we identified carriers of ALG9 loss-of-function mutations and noncarrier matched controls in a large exome-sequenced population-based cohort and evaluated the occurrence of polycystic phenotypes in both groups.

RESULTS

Two patients in the clinically defined cohort had rare loss-of-function variants in ALG9, which encodes a protein required for addition of specific mannose molecules to the assembling N-glycan precursors in the endoplasmic reticulum lumen. In vitro assays showed that inactivation of Alg9 results in impaired maturation and defective glycosylation of PC1. Seven of the eight (88%) cases selected from the population-based cohort based on ALG9 mutation carrier state who had abdominal imaging after age 50; seven (88%) had at least four kidney cysts, compared with none in matched controls without ALG9 mutations.

CONCLUSIONS

ALG9 is a novel disease gene in the genetically heterogeneous ADPKD spectrum. This study supports the utility of phenotype characterization in genetically-defined cohorts to validate novel disease genes, and provide much-needed genotype-phenotype correlations.

The Urological Association of Asia clinical guideline for urinary stone disease

The Urological Association of Asia, consisting of 25 member associations and one affiliated member since its foundation in 1990, has planned to develop Asian guidelines for all urological fields. The field of stone diseases is the third of its guideline projects. Because of the different climates, and social, economic and ethnic environments, the clinical practice for urinary stone diseases widely varies among the Asian countries. The committee members of the Urological Association of Asia on the clinical guidelines for urinary stone disease carried out a surveillance study to better understand the diversity of the treatment strategy among different regions and subsequent systematic literature review through PubMed and MEDLINE database between 1966 and 2017. Levels of evidence and grades of recommendation for each management were decided according to the relevant strategy. Each clinical question and answer were thoroughly reviewed and discussed by all committee members and their colleagues, with suggestions from expert representatives of the American Urological Association and European Association of Urology. However, we focused on the pragmatic care of patients and our own evidence throughout Asia, which included recent surgical trends, such as miniaturized percutaneous nephrolithotomy and endoscopic combined intrarenal surgery. This guideline covers all fields of stone diseases, from etiology to recurrence prevention. Here, we present a short summary of the first version of the guideline - consisting 43 clinical questions - and overview its key practical issues.

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.

No Reported Renal Stones with Intravenous Vitamin C Administration: A Prospective Case Series Study

A few cases associating high dose intravenous vitamin C (IVC) administration with renal stone formation have been reported in the literature, however, no long-term studies investigating IVC administration and reported renal stones have been carried out. Our aim was to measure the frequency of reported renal stones in patients receiving IVC therapy. We carried out a prospective case series study of 157 adult patients who commenced IVC therapy at Integrated Health Options clinic between 1 September 2011 and 31 August 2012, with follow-up for 12 months. Inquiries into the occurrence of renal stones were conducted at enrolment, 6 and 12 months, and renal function blood tests were conducted at enrolment, 4 weeks and every 12 weeks thereafter in a subgroup of patients. No renal stones were reported by any patients in the study, despite 8% of the patients having a history of renal stones. In addition, the majority of patients investigated had stable renal function during the study period as evidenced by little change in serum creatinine levels and estimated glomerular filtration rate (eGFR) following IVC. In conclusion, IVC therapy was not associated with patient-reported renal stones. Although not the primary focus of this study, it was also observed that there was no significant change in mean serum creatinine or eGFR for those who had follow-up renal function blood tests.

Oral Antibiotic Exposure and Kidney Stone Disease

Background Although intestinal and urinary microbiome perturbations are associated with nephrolithiasis, whether antibiotics are a risk factor for this condition remains unknown.Methods We determined the association between 12 classes of oral antibiotics and nephrolithiasis in a population-based, case-control study nested within 641 general practices providing electronic health record data for >13 million children and adults from 1994 to 2015 in the United Kingdom. We used incidence density sampling to match 25,981 patients with nephrolithiasis to 259,797 controls by age, sex, and practice at date of diagnosis (index date). Conditional logistic regression models were adjusted for the rate of health care encounters, comorbidities, urinary tract infections, and use of thiazide and loop diuretics, proton-pump inhibitors, and statins.Results Exposure to any of five different antibiotic classes 3-12 months before index date was associated with nephrolithiasis. The adjusted odds ratio (95% confidence interval) was 2.33 (2.19 to 2.48) for sulfas, 1.88 (1.75 to 2.01) for cephalosporins, 1.67 (1.54 to 1.81) for fluoroquinolones, 1.70 (1.55 to 1.88) for nitrofurantoin/methenamine, and 1.27 (1.18 to 1.36) for broad-spectrum penicillins. In exploratory analyses, the magnitude of associations was greatest for exposure at younger ages (P<0.001) and 3-6 months before index date (P<0.001), with all but broad-spectrum penicillins remaining statistically significant 3-5 years from exposure.Conclusions Oral antibiotics associated with increased odds of nephrolithiasis, with the greatest odds for recent exposure and exposure at younger age. These results have implications for disease pathogenesis and the rising incidence of nephrolithiasis, particularly among children.

SaRNA-mediated activation of TRPV5 reduces renal calcium oxalate deposition in rat via decreasing urinary calcium excretion

Hypercalciuria is a main risk factor for kidney stone  formation. TRPV5 is the gatekeeper protein for mediating calcium transport and reabsorption in the kidney. In the present study, we tested the effect of TRPV5 activation with small activating RNA (saRNA), which could induce gene expression by targeting the promoter of the gene, on ethylene glycol (EG)-induced calcium oxalate (CaOx) crystals formation in rat kidney. Five pairs of RNA activation sequences targeting the promoter of rat TRPV5 were designed and synthesized. The synthesized saRNA with the strongest activating effect was selected, and transcellular calcium transportation was tested by Fura-2 analysis. Subsequently, Sprague-Dawley rats were equally divided into three groups and fed with water, 1% EG for 28 days after injecting the negative control saRNA, 1% EG for 28 days after injecting the selected TRPV5-saRNA, respectively. The CaOx crystal formation and the 24-h urine components were assessed. In vitro study, saRNA ds-320 could significantly activate the expression of TRPV5 and transcellular calcium transportation. In vivo study, after 28 days treatment of EG, rats pre-infected with saRNA ds-320 had lower urinary calcium excretion and renal CaOx crystals formation as compared to that pre-infected with negative control saRNA. Activation of TRVP5 with saRNA ds-320 could inhibit EG-induced calcium oxalate crystals formation via promoting urine calcium reabsorption and decreasing urine calcium excretion in rats.

The efficacy of a shared-care surveillance protocol for asymptomatic renal calculi

Objective:

Patients at our institution with asymptomatic calyceal stones (<11 mm) are discharged to their GPs with a request for 12- and 24-month X-ray KUBs with specific re-referral criteria. We aimed to assess the effectiveness of this shared care protocol as well as to investigate long-term outcomes.

Patients and methods:

All patients satisfying the above criteria discharged during October 2009–June 2011 were reviewed for protocol compliance, symptomatic events and/or surgical intervention up to July 2015.

Results:

A total of 134 patients were identified. Out of 115 patients eligible for their first X-ray, and 100 patients eligible for their second X-ray, 43% and 26% respectively were performed. Of these, 75% demonstrated no progression. No patients were treated surgically solely on the basis of radiographic progression. Over a mean five-year follow-up, patients had a 39% chance of experiencing a symptomatic event and a 24% chance of requiring surgical intervention (ESWL, ureteroscopy and/or PCNL). Risk factors included a previous stone history and having a total stone size >10 mm.

Conclusion:

There was poor adherence to this protocol. Despite this, only symptomatic patients were treated surgically, challenging the value of indefinite surveillance of asymptomatic patients. Longitudinal studies are needed to determine a cost-effective manner in which these patients can be safely followed up.

If You Twinkle When You Tinkle, Stones Are Found on Ultrasound

Urolithiasis in children is an underrecognized cause of pediatric abdominal pain. Our case describes a child who presented to the emergency department with right lower quadrant pain, in whom a point-of-care ultrasound detected an ureterovesicular stone, which obviated the need for any further radiographic studies. We review the current literature on pediatric urolithiasis with a focus on sonographic diagnosis.

Costs for in hospital treatment of urinary lithiasis in the Brazilian public health system

OBJECTIVE

To estimate costs associated to hospital treatment of urinary lithiasis in the Brazilian public health system as well as to evaluate demographic and epidemiological data referred to hospital admissions in the Brazilian public health system (or unified health care system).

METHODS

Data from the Informatic Department of Brazilian public health system were obtained as referred to costs in hospital admissions for urinary lithiasis during 2010 and also epidemiological data from 1996 through 2010.

RESULTS

There were 69,039 hospital admissions for urinary lithiasis, totaling 0.61% of all hospital admissions in the Brazilian public health system. The mean cost of each of these hospital admissions was US$ 240,23 or R$ 423.42 having as result an overall cost of US$ 16,240,378.00 or R$ 29.232.682,56. Hospital admissions for urinary lithiasis in the Brazilian public health system increased 69% from 1996 to 2010 (43,176 versus 69,309; p < 0.001; OR = 1.69). The number of hospital admissions was 5% greater between December and March as compared to the period between June and September (35,290 versus 33,749; p < 0.001; OR = 1.10). For Caucasian patients the hospital admission was 75% greater as compared to black patients (63.2% versus 35.8%; p = 0.02; OR = 1,75).

CONCLUSION

Hospital admission for urinary liyhiasis has an elevated impact on the public health system with a cost of US$ 16,2 or R$ 29.2 million per year. The number of hospital admissions was greater in hotter months than in cold ones and also in the last decade, mainly in Caucasian population. These data may be helpful for the organization and optimization of health programs in the public health system as referred to prevention and treatment of urinary lithiasis in Brazil.

Prevalence of kidney stones and vertebral fractures in primary hyperparathyroidism using imaging technology

CONTEXT

The fourth International Workshop on the Management of Asymptomatic Primary Hyperparathyroidism (PHPT) has recently suggested that skeletal and renal imaging be routinely conducted. So far, no study has systematically assessed this issue.

OBJECTIVE

The objective was to evaluate the prevalence of kidney stones (KS) and vertebral fractures (VFs) in a cohort of patients with PHPT utilizing noninvasive imaging technology.

DESIGN

This was a prospective study evaluating patients consecutively diagnosed with PHPT in a single center over a 5-year period (2009-2013).

SETTING

The setting was a referral center.

PATIENTS

There were a total of 140 patients with PHPT (127 women [18 premenopausal and 109 postmenopausal] and 13 men; mean age, 63.2 ± 11 y).

MAIN OUTCOMES MEASURES

Main outcome measures were the prevalence of KS by abdominal ultrasound, osteoporosis by dual-energy x-ray absorptiometry (DXA) (lumbar spine, femoral neck, total hip, and distal 1/3 radius), and VFs by vertebral spine x-ray, with attention to those categorized as symptomatic or asymptomatic.

RESULTS

Fifty-five percent of all subjects had KS by ultrasound, 62.9% had osteoporosis by T-score at any site, and 35.1% had VFs by x-ray. There was no difference in the incidence of VFs and densitometric osteoporosis between symptomatic and asymptomatic patients (VFs, 34.4 vs 34.7%; osteoporosis by DXA, 59.4 vs 65.8%), whereas more KS were detected in symptomatic (78%) than asymptomatic (35.5%). Twenty-two percent of patients classified as asymptomatic at baseline without osteoporosis by DXA were found to have KS and/or VFs.

CONCLUSIONS

Nephrolithiasis and VFs are common in asymptomatic subjects with PHPT. The results provide evidence in support of recent recommendations that a more proactive approach be taken to detect silent bone and stone disease in asymptomatic PHPT.

The natural history of nonobstructing asymptomatic renal stones managed with active surveillance

PURPOSE

We documented the natural history of asymptomatic nonobstructing renal calculi managed with active surveillance and explored factors predicting stone related events to better inform shared decision making.

MATERIALS AND METHODS

Patients with asymptomatic nonobstructing renal calculi electing active surveillance of their stone(s) were retrospectively reviewed. Stone characteristics, patient characteristics, and stone related events were collected. We evaluated the effects of stone size and location on development of symptoms, spontaneous passage, requirement for surgical intervention, and stone growth.

RESULTS

We identified 160 stones with an average size of 7.0 ± 4.2 mm among 110 patients with average followup of 41 ± 19 months. Forty-five (28% of total) stones caused symptoms during followup. Notably 3 stones (3% of asymptomatic subgroup, 2% of total stones) caused painless silent obstruction necessitating intervention after an average of 37 ± 17 months. The only significant predictor of spontaneous passage or symptom development was location. Upper pole/mid renal stones were more likely than lower pole stones to become symptomatic (40.6% vs 24.3%, p = 0.047) and to pass spontaneously (14.5% vs 2.9%, p = 0.016).

CONCLUSIONS

Among asymptomatic nonobstructing renal calculi managed with active surveillance, most remained asymptomatic through an average followup of more than 3 years. Less than 30% caused renal colic, less than 20% were operated on for pain and 7% spontaneously passed. Lower poles stones were significantly less likely to cause symptoms or pass spontaneously. Despite 3 stones causing silent hydronephrosis suggestive of obstruction, regular followup imaging facilitated interventions that prevented renal loss.

The ROKS nomogram for predicting a second symptomatic stone episode

Most patients with first-time kidney stones undergo limited evaluations, and few receive preventive therapy. A prediction tool for the risk of a second kidney stone episode is needed to optimize treatment strategies. We identified adult first-time symptomatic stone formers residing in Olmsted County, Minnesota, from 1984 to 2003 and manually reviewed their linked comprehensive medical records through the Rochester Epidemiology Project. Clinical characteristics in the medical record before or up to 90 days after the first stone episode were evaluated as predictors for symptomatic recurrence. A nomogram was developed from a multivariable model based on these characteristics. There were 2239 first-time adult kidney stone formers with evidence of a passed, obstructing, or infected stone causing pain or gross hematuria. Symptomatic recurrence occurred in 707 of these stone formers through 2012 (recurrence rates at 2, 5, 10, and 15 years were 11%, 20%, 31%, and 39%, respectively). A parsimonious model had the following risk factors for recurrence: younger age, male sex, white race, family history of stones, prior asymptomatic stone on imaging, prior suspected stone episode, gross hematuria, nonobstructing (asymptomatic) stone on imaging, symptomatic renal pelvic or lower-pole stone on imaging, no ureterovesicular junction stone on imaging, and uric acid stone composition. Ten-year recurrence rates varied from 12% to 56% between the first and fifth quintiles of nomogram score. The Recurrence of Kidney Stone nomogram identifies kidney stone formers at greatest risk for a second symptomatic episode. Such individuals may benefit from medical intervention and be good candidates for prevention trials.

Prophylactic effects of quercetin and hyperoside in a calcium oxalate stone forming rat model

Quercetin and hyperoside (QH) are the two main constituents of the total flavone glycosides of Flos Abelmoschus manihot, which has been prescribed for treating chronic kidney disease for decades. This study aimed to investigate the effect of QH on calcium oxalate (CaOx) formation in ethylene glycol (EG)-fed rats. Rats were divided into three groups: an untreated stone-forming group, a QH-treated stone-forming group (20 mg/kg/day) and a potassium citrate-treated stone-forming group (potassium citrate was a worldwide-recognized calculi-prophylactic medicine). Ethylene glycol (0.5 %) was administered to the rats during the last week, and vitamin D3 was force-fed to induce hyperoxaluria and kidney calcium oxalate crystal deposition. 24 h urine samples were collected before and after inducing crystal deposits. Rats were killed and both kidneys were harvested after 3 weeks. Bisected kidneys were examined under a polarized light microscope for semi-quantification of the crystal-formation. The renal tissue superoxide dismutase and catalase levels were measured by Western blot. QH and potassium citrate have the ability to alkalinize urine. The number of crystal deposits decreased significantly in the QH-treated stone-forming group as compared to the other groups. Superoxide dismutase and catalase levels also increased significantly in the QH-treated stone-forming group, as compared with the untreated stone-forming group. QH administration has an inhibitory effect on the deposition of CaOx crystal in EG-fed rats and may be effective for preventing stone-forming disease.

Nephrolithiasis in patients with inflammatory bowel disease in the community

Background

Inflammatory bowel disease (IBD) has been associated with renal stone formation. The objective of this study was to determine prospectively the prevalence of nephrolithiasis in a community-based population of patients with IBD and to analyze factors associated with renal calculus formation.

Methods

Screening renal ultrasound was performed in a well characterized cohort of patients seen between 2009 and 2012 at an IBD clinic. We enrolled 168 patients, including 93 with Crohn’s disease and 75 with ulcerative colitis. Clinical and phenotypic variables associated with asymptomatic nephrolithiasis were determined.

Results

Nephrolithiasis was detected in 36 patients with Crohn’s disease and in 28 patients with ulcerative colitis (38% for both). Although none of the patients had been previously hospitalized for symptomatic nephrolithiasis, nine with Crohn’s disease and five with ulcerative colitis had recurrent urinary tract infections or hydronephrosis. In patients with Crohn’s disease, ileocolonic (L3) disease was associated with a greater risk of nephrolithiasis than was ileal (L1) or colonic (L2) disease (odds ratio [OR] 2.3, 95% confidence interval [CI] 1.8–7). Active ulcerative colitis (regardless of severity) represented a significant risk factor for formation of renal calculi (OR 4.2, 95% CI 1.1–15, P = 0.02).

Conclusion

In surgery-naïve patients with IBD in the community, asymptomatic nephrolithiasis is common and should be considered when renal dysfunction or infection is detected.

Natural history of asymptomatic renal stones and prediction of stone related events

PURPOSE

The appropriate management for asymptomatic renal stones remains unclear. We assessed the natural history and progression rate of such stones and identified clinical factors associated with an increased risk of stone related events.

MATERIALS AND METHODS

We retrospectively reviewed the medical records of 201 male and 146 female patients with asymptomatic renal stones. It was recommended that patients be followed every 6 months. Mean followup was 31 months (range 6 to 180). Patients were divided into 2 groups by stone related events, including spontaneous stone passage, flank pain, stone growth or the need for intervention during followup.

RESULTS

Spontaneous passage occurred in 101 patients (29.1%). Of the patients 186 (53.6%) and 161 (46.4%) did and did not have stone related events, respectively. Of the whole cohort 85 patients (24.5%) required intervention but only 4.6% needed surgery. At 19 months after diagnosis 50% of the patients had a symptom. Those with stone related events were more likely to be younger (mean ± SD age 46.6 ± 12.7 vs 49.3 ± 12.6 years) and male, and have a stone history (p = 0.047, 0.017 and 0.014, respectively). Male gender significantly decreased the probability of freedom from stone related events (log rank test p = 0.0135) and it was an independent predictor of stone related events (HR 1.521, p = 0.009). Younger patients, and those with smaller stones and no stone growth were more likely to experience spontaneous passage and less likely to undergo intervention (each p <0.05).

CONCLUSIONS

Asymptomatic renal stones can be followed safely but long-term followup is necessary. Periodic followup and early intervention should be recommended in patients with risk factors.

Temporal trends in the incidence of kidney stone disease

Recent reports show an increased occurrence of kidney stone disease worldwide. To further evaluate and quantify this observation, we examined recent trends in the incidence of kidney stone disease in the adult population of Iceland over a 24-year period. Computerized databases of all major hospitals and medical imaging centers in Iceland were searched for International Classification of Diseases, radiologic and surgical procedure codes indicative of kidney stones in patients aged 18 years and older. The time trends in stone frequency of 5945 incident patients (63% men) were assessed by Poisson regression analysis. The majority of patients (90.5%) had symptomatic stone disease. The total incidence of kidney stones rose significantly from 108 per 100,000 in the first 5-year interval of the study to 138 per 100,000 in the last interval. The annual incidence of symptomatic stones did not increase significantly in either men or women. There was, however, a significant increase in the annual incidence of asymptomatic stones over time, from 7 to 24 per 100,000 for men and from 7 to 21 per 100,000 for women. The increase in the incidence of asymptomatic stones was only significant for women above 50 years of age and for men older than 40 years. Thus, we found a significant increase in the incidence of kidney stone disease resulting from increased detection of asymptomatic stones. This was largely due to a more frequent use of high-resolution imaging studies in older patients.

Ambient temperature as a contributor to kidney stone formation: implications of global warming

Nephrolithiasis is a common disease across the world that is becoming more prevalent. Although the underlying cause for most stones is not known, a body of literature suggests a role of heat and climate as significant risk factors for lithogenesis. Recently, estimates from computer models predicted up to a 10% increase in the prevalence rate in the next half century secondary to the effects of global warming, with a coinciding 25% increase in health-care expenditures. Our aim here is to critically review the medical literature relating stones to ambient temperature. We have categorized the body of evidence by methodology, consisting of comparisons between geographic regions, comparisons over time, and comparisons between people in specialized environments. Although most studies are confounded by other factors like sunlight exposure and regional variation in diet that share some contribution, it appears that heat does play a role in pathogenesis in certain populations. Notably, the role of heat is much greater in men than in women. We also hypothesize that the role of a significant human migration (from rural areas to warmer, urban locales beginning in the last century and projected to continue) may have a greater impact than global warming on the observed worldwide increasing prevalence rate of nephrolithiasis. At this time the limited data available cannot substantiate this proposed mechanism but further studies to investigate this effect are warranted.

Clinical characteristics of potential kidney donors with asymptomatic kidney stones

BACKGROUND

Patients with symptomatic kidney stones are characterized by older age, male gender, white race, hypertension, obesity, metabolic syndrome and chronic kidney disease. Whether these characteristics differ in patients with asymptomatic kidney stones is unknown.

METHODS

All potential kidney donors who underwent protocol computed tomography angiograms/urograms (2000-08) at the Mayo Clinic were identified. Renal abnormalities, including kidney stones, were assessed radiographically. Comorbidities, including past symptomatic kidney stones, were abstracted from the medical record. Characteristics of persons with and without radiographic stones were compared. Stone burden among persons with and without past symptomatic stones was compared.

RESULTS

Among 1957 potential kidney donors, 3% had past symptomatic stones and 11% had radiographic stones (10% had only asymptomatic radiographic stones). Asymptomatic stone formers were more likely to be of white race, have low urine volumes and have radiographic findings of renal parenchymal thinning, focal renal scarring, medullary sponge kidney and polycystic kidney disease. Asymptomatic stone formers were not characterized by older age, male gender, hypertension, obesity, metabolic syndrome, abnormal kidney function, hyperuricemia, hypercalcemia or hypophosphatemia. Among persons with radiographic stones, those with past symptomatic stones had a slightly higher number of stones (mean 2.7 versus 2.4; P = 0.04), but a much greater diameter for the largest stone (mean 4.8 versus 1.6 mm; P < 0.001).

CONCLUSIONS

Asymptomatic kidney stone formers have different demographic characteristics and many lack the comorbidities that have been described in persons with symptomatic kidney stones. These findings suggest that different pathophysiologic mechanisms could be involved in asymptomatic stone formation versus symptomatic stone passage.