Changes in upper urinary tract stone composition in Australia over the past 30 years

Spectrum of Bacterial Pathogens from Urinary Infections Associated with Struvite and Metabolic Stones

OBJECTIVE

The purposes of this multi-center study were to evaluate the rate of infection stones and to evaluate the urine cultures of patients with infection stones.

MATERIALS

Charts of adulpatients with urinary stones were reviewed and data on stone analyses and urine cultures were collected.

RESULTS

In total, 1204 renal stone formers (RSFs) from 10 countries were included (776 males, 428 females). Fifty-six patients (4.6%) had struvite stones. The highest frequency of struvite stones was observed in India (23%) and Pakistan (18%). Lower rates were reported in Canada (2%), China (3%), Argentina (3%), Iraq (3%), Italy (3.5%) and Poland (3%), and intermediate rates in Egypt (5.5%) and Bulgaria (5.4%). Urine cultures were retrieved from 508 patients. Patients with struvite stones had a positive culture in 64.3% of the samples and patients with other stones, in 26.7%. In struvite stones, the most common isolates were Escherichia coli (27.7%) and Proteus spp. (27.7%), followed by Klebsiella spp. (16.7%); in other types of stone, it was Escherichia coli (47.6%), followed by Gram-positive bacteria (14.0%) Conclusions: The struvite stone composition was associated with a urinary infection, although an infection was not demonstrable with a conventional midstream urine culture in about 30%.

A 15-year longitudinal analysis of the trends in the surgical management of renal and ureteric stones in Australia

Objective:

This study evaluates the evolving surgical management of renal stones in Australia over the past 15 years.

Methods:

The National Australian Medicare and Australian Institute of Health and Welfare (AIWH) data were used to obtain the annual number of hospital presentations for urolithiasis and surgical procedures for upper urinary tract stones from 2005 to 2020. The four treatment modalities observed included nephrolithotomy, shockwave lithotripsy (SWL), percutaneous nephrolithotomy (PCNL) and endoscopic lithotripsy.

Results:

The total number of renal colic presentations in Australian hospitals and urology procedures claimed by Medicare has increased during the past 15 years. A total of 218,999 urological procedures were claimed by Medicare for renal stones over 15 years. There has been a dramatic rise in endoscopic lithotripsy surgery for stones. In 2005–2006, endoscopic lithotripsy comprised 56.6% of total stonework claimed by Medicare, and this proportion jumped to 88.9% in 2019–2020. All other modalities saw a decline in absolute and relative numbers.

Conclusion:

Endoscopic management of upper renal tract stones predominates in the current management of renal stone disease in Australia. Epidemiology audits such as this study can provide insight into national disease trends and guide future healthcare policies and resource planning.

Level of evidence:

2b

Epidemiological trends of urinary tract infections, urolithiasis and benign prostatic hyperplasia in 203 countries and territories from 1990 to 2019

BACKGROUND

Urinary tract infections (UTI), urolithiasis, and benign prostatic hyperplasia (BPH) are three of the most common nonmalignant conditions in urology. However, there is still a lack of comprehensive and updated epidemiological data. This study aimed to investigate the disease burden of UTI, urolithiasis, and BPH in 203 countries and territories from 1990 to 2019.

METHODS

Data were extracted from the Global Burden of Disease 2019, including incident cases, deaths, disability-adjusted life-years (DALYs) and corresponding age-standardized rate (ASR) from 1990 to 2019. Estimated annual percentage changes (EAPC) were calculated to evaluate the trends of ASR. The associations between disease burden and social development degrees were analyzed using a sociodemographic index (SDI).

RESULTS

Compared with 1990, the incident cases of UTI, urolithiasis, and BPH increased by 60.40%, 48.57%, and 105.70% in 2019, respectively. The age-standardized incidence rate (ASIR) of UTI increased (EAPC = 0.08), while urolithiasis (EAPC = - 0.83) and BPH (EAPC = - 0.03) decreased from 1990 to 2019. In 2019, the age-standardized mortality rate (ASMR) of UTI and urolithiasis were 3.13/100,000 and 0.17/100,000, respectively. BPH had the largest increase (110.56%) in DALYs in the past three decades, followed by UTI (68.89%) and urolithiasis (16.95%). The burden of UTI was mainly concentrated in South Asia and Tropical Latin America, while the burden of urolithiasis and BPH was recorded in Asia and Eastern Europe. Moreover, the ASIR and SDI of urolithiasis in high-SDI regions from 1990 to 2019 were negatively correlated, while the opposite trend was seen in low-SDI regions. In 2019, the ASIR of UTI in females was 3.59 times that of males, while the ASIR of urolithiasis in males was 1.96 times higher than that in females. The incidence was highest in the 30-34, 55-59, and 65-69 age groups among the UTI, urolithiasis, and BPH groups, respectively.

CONCLUSION

Over the past three decades, the disease burden has increased for UTI but decreased for urolithiasis and BPH. The allocation of medical resources should be based more on the epidemiological characteristics and geographical distribution of diseases.

Association between aortic calcification and the presence of kidney stones: calcium oxalate calculi in focus

PURPOSE

The current research is aimed at analyzing the relationship between kidney stone (KS) and abdominal aortic calcification (AAC) and the relationship between KS components and AAC.

METHODS

This is a retrospective, case-control study. Kidney stone formers (KSFs) were treated at the Department of Urology, West China Hospital, Sichuan University for urological calculus disease from January 2014 to January 2020. Matched non-stone formers (non-SFs) were drawn from the same hospital for routine health examination from January 2018 to February 2019. Research-related information was collected and reviewed retrospectively from the hospital's computerized records. AAC were evaluated using available results of computed tomography imaging and abdominal vascular ultrasound. The relationships of AAC between KSFs and non-SFs were compared. The composition of renal calculi was analyzed by Fourier-transform infrared spectrophotometer. KSFs were divided into AAC groups and non-AAC based on AAC. The relationship of the composition of renal calculi between AAC and non-AAC were compared. The independent-sample t test, the chi-squared test and binary logistics regression were performed.

RESULTS

Altogether, 4516 people were included, with 1027 KSFs and 3489 non-SFs. There were no significant differences in the laboratory parameters between KSFs and non-SFs. The association between the presence of AAC and KS was significant in multivariable model 2 [adjusting hypertension, diabetes mellitus, fasting blood glucose, uric acid, serum triglyceride (TG), serum calcium, and urine pH] (OR 5.756, 95% CI 4.616-7.177, p < 0.001). The result of KSFs showed that calcium oxalate calculi (CaOx) was significantly associated with AAC in multivariable model 3 (adjusting age, hypertension, diabetes mellitus, drinking history, smoking history, and TG) (OR 1.351, 95% CI 1.002-1.822, p = 0.048).

CONCLUSIONS

The current study pioneered the revelation of the relationship between CaOx and AAC. Through an elimination of the confounding factors, the study demonstrated that KS and AAC were connected.

Trends in urinary stone composition in 23,182 stone analyses from 2011 to 2019: a high-volume center study in China

PURPOSE

To evaluate the distribution and dynamic trends in constituents of urinary stones in China.

MATERIALS AND METHODS

The composition of 23,182 stones were analyzed and then recorded between January 2011 and December 2019. The characteristics in terms of stone patient's gender, age and calendar year were analyzed.

RESULTS

Most stones (22,172, 95.64%) had several crystal components, among which 40.25% (8925/22,172) were mixtures with infection components. Calcium oxalate (CaOx) and uric acid (UA) stones were more commonly encountered in men, but calcium phosphate (CaP), magnesium ammonium phosphate (MAP) and carbonate apatite (CA) stones were more prevalent in women (p < 0.05). In males, the proportion of CaOx stones increased up to the age of 40, but subsequently decreased (p < 0.001). Interestingly, females showed an inverse trend regarding CaOx stones (p < 0.001). The proportion of UA stones increased with age (p < 0.001), and CA stones most frequently were recorded at age 20-49. Over the past 9 years, UA, CA, and MAP stones increased over time, whereas there was a tendency for CaOx stones to decrease (p < 0.05).

CONCLUSIONS

The scarcity of pure stones and a certain proportion of mixtures with infection stone components (e.g., mixtures of CaOx and CA) suggest that treatment directed against a single stone component is insufficient for effective recurrence prevention. Age and gender were significant determinants of stone composition, and according to the observed chronological trends, it seems that in the future, more UA, CA and MAP stones and fewer CaOx stones may be encountered in the studied population.

Time changes in the spectrum of urinary stone composition: a role for climate variations?

BACKGROUND

An increase of the frequency of uric acid urinary stones compared to calcium-containing ones has been recently described. This study was aimed at assessing the frequency of different types of urinary stones in the population of northern Italy in the period 2016-18 compared to 2001-2003.

METHODS

Analyses by infrared spectroscopy of 1007 stones endoscopically removed at two institutions in the area of Milan (Northern Italy) were retrospectively considered. Stones were classified as calcium oxalate monohydrate (COM) and dihydrate (COD), mixed uric acid/calcium oxalate (UC); uric acid (UA), struvite (ST); apatite (CAP); mixed calcium oxalate / apatite (CAPOX); others. The patients were divided into two groups: 2001-2003 and 2016-2018. The average temperature values of the region over the two time periods were obtained by the national statistical institute.

RESULTS

The average age of the 2001-2003 group (45.8+/- 15.4 years) was significantly lower than the average age of the 2016-18 group (57.9+/- 14.8) (0.000). M / F ratio was similar in the two groups: 119 / 69 (1,0.58) in 2001-2003 and 527 / 292 (1,0.55) in 2016-18 (p = 0.862). COM stones tended to more frequent in 2016-18 group than in 2001-03. COD stones were significantly more frequent in 2001-03 than in 2016-18. ST stone frequency was increased from 2001 to 03 to 2016-18. No increase of uric acid containing stones was observed in 2016-18. Results were confirmed after adjustment by age. Averages annual regional temperatures increased from 14 °C to 15.4 °C during the two observation periods.

CONCLUSIONS

No increase of UA stones was observed, probably due to the limited impact of the global warming in our temperate climate.

Identifying community chronic kidney disease risk profile utilising general practice clinical records and spatial analysis: approach to inform policy and practice

BACKGROUND

Chronic kidney disease (CKD) causes a significant health burden in Australia, and up to 50% of Australians with CKD remain undiagnosed.

AIMS

To estimate the 5-year risk for CKD from general practice (GP) clinical records and to investigate the spatial variation and hot spots of CKD risk in an Australian community.

METHOD

A cross-sectional study was designed using de-identified GP clinical data recorded from 2010 to 2015. A total of 16 GP participated in this study from West Adelaide, Australia. We used health records of 36 565 patients aged 35-74 years, with no prior history of CKD. The 5-year estimated CKD risk was calculated using the QKidney algorithm. Individuals' risk score was aggregated to Statistical Area Level 1 to predict the community CKD risk. A spatial hotspot analysis was applied to identify the communities with greater risk.

RESULTS

The mean estimated 5-year risk for CKD in the sample population was 0.95% (0.93-0.97). Overall, 2.4% of the study population was at high risk of CKD. Significant hot spots and cold spots of CKD risk were identified within the study region. Hot spots were associated with lower socioeconomic status.

CONCLUSIONS

This study demonstrated a new approach to explore the spatial variation of CKD risk at a community level, and implementation of a risk prediction model into a clinical setting may aid in early detection and increase disease awareness in regions of unmet CKD care.

The status and characteristics of urinary stone composition in China

OBJECTIVES

To explore characteristics of urinary stone composition in China, and determine the effects of gender, age, body mass index (BMI), stone location, and geographical region on stone composition.

PATIENTS AND METHODS

We prospectively used Fourier-transform infrared spectroscopy to analyse stones from consecutive patients presenting with new-onset urolithiasis at 46 hospitals in seven geographical areas of China, between 1 June 2010 and 31 May 2015. Chi-squared tests and logistic regression analyses were used to determine associations between stone composition and gender, age, BMI, stone location, and geographical region.

RESULTS

The most common stone constituents were: calcium oxalate (CaOx; 65.9%), carbapatite (15.6%), urate (12.4%), struvite (2.7%), and brushite (1.7%). CaOx and urate stones occurred more frequently in males, whereas carbapatite and struvite were more common in females (P < 0.01). CaOx and carbapatite were more common in those aged 30-50 and 20-40 years than in other groups. Brushite and struvite were most common amongst those aged <20 and >70 years. The detection rate of urate increased with age, whilst cystine decreased with age. Obese patients were more likely to have urate stones than carbapatite or brushite stones (P < 0.01). CaOx, carbapatite, brushite, and cystine stones were more frequently found in the kidney than other types, whereas urate and struvite were more frequent in the bladder (P < 0.01). Stone composition varied by geographical region.

CONCLUSIONS

The most common stone composition was CaOx, followed by carbapatite, urate, struvite, and brushite. Stone composition differed significantly in patients grouped by gender, age, BMI, stone location, and geographical region.

Activities of Ca2+-related ion channels during the formation of kidney stones in an infection-induced urolithiasis rat model

Bacterial infection has long been recognized to contribute to struvite urinary stone deposition; however, its contribution to the development of chronic kidney stones has not been extensively investigated. In the present study, we hypothesized another possible method of bacteria contributing to the formation of calcium oxalate (CaOx) that accounts for the biggest part of the kidney stone. Bacteria may play important roles by influencing renal Ca²⁺-related ion channel activities, resulting in chronic inflammation of the kidney along with rapid aggregation of stones. We examined the correlation among infection-promoted CaOx kidney stones and alterations in Ca²⁺-related ion channels in an animal model with experimentally induced Proteus mirabilis and foreign body infection. After the bladder was infected for 7 days, the data demonstrated that stones were presented and induced severe renal tubular breakage as well as altered levels of monocyte chemoattractant protein-1, cyclooxygenase-2, osteopontin, and transient receptor potential vanilloid member 5 expression, reflecting responses of kidney ion channels. Monocyte chemoattractant protein-1, osteopontin, and transient receptor potential vanilloid member 5 expression was significantly downregulated over time, indicating the chronic inflammation phase of the kidney and accelerated aggregation of CaOx crystals, respectively, whereas cyclooxygenase-2 exhibited no differences. These results indicated that bacterial infection is considerably correlated with an alteration in renal Ca²⁺-related ion channels and might support specific and targeted Ca²⁺-related ion channel-based therapeutics for urolithiasis and related inflammatory renal damage.

Trends in urinary calculi composition from 2005 to 2015: a single tertiary center study

The goal of this study was to investigate recent changes in stone composition and patient demographics to identify factors influencing stone formation for the purpose of reducing the incidence of urolithiasis and preventing stone recurrence. This retrospective analysis includes patients who underwent percutaneous nephrolithotripsy or ureteroscopy at our institution from 2005 to 2015. Northwestern Medicine Enterprise Data Warehouse was used to retrieve demographic information and stone composition analyses. The composition of mixed stones containing uric acid (UA) and calcium oxalate monohydrate (COM) was analyzed further. Chi-squared tests were used for categorical variables and logistic regression was used to assess trends. From 2005 to 2015, 5268 stones were treated. COM was predominant in 42.2% and only 16.6% were pure. The male/female ratio decreased significantly from 1.8 to 1.08 and patient age increased (p < 0.001) with 45.6% of patients being 60 or older in 2015. Females formed more CO dihydrate (COD; p = 0.008) and struvite (p = 0.001) overall. The incidence of COM (p = 0.007) and UA (p < 0.001) rose significantly in men whereas both sexes saw a decrease in carbonate apatite (CA; p < 0.001). COM increased considerably from 12 to 75% amongst mixed stones with UA over the 11-year span. We concluded that stone formers have become older and more gender-equal. The increase in female patients parallels the increase in female obesity in the US. The rising predominance of COM, including when mixed with UA, and the scarcity of pure stones indicates it may be necessary to develop new approaches to managing and preventing urolithiasis.

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.

Mediators of the Effects of Gender on Uric Acid Nephrolithiasis: A Novel Application of Structural Equation Modeling

Numerous epidemiological studies have shown that male patients with uric acid nephrolithiasis outnumber female patients. To our knowledge, no research exists evaluating the reasons gender affects the development of uric acid nephrolithiasis. We hereby used a novel application of structural equation modeling to analyze the mediators of the effects of gender on uric acid nephrolithiasis. In 1,098 patients with nephrolithiasis between 2012 and 2016, male gender was found to have a statistically significant positive indirect effect on the development of uric acid nephrolithiasis, which was mediated by lower urine pH (estimate: 0.010, standard error: 0.005, critical ratio: 2.135, 95% confidence interval: 0.002–0.023, P = 0.017), lower estimated glomerular filtration rate (estimate: 0.014, standard error: 0.005, critical ratio: 2.993, 95% confidence interval: 0.006–0.025, P < 0.001), and higher incidence rate of gout (estimate: 0.009, standard error: 0.005, critical ratio: 2.028, 95% confidence interval: 0.002–0.021, P = 0.009). We conclude that low urine pH, impaired renal function, and gout are the mediators of the effect of male gender on the development of uric acid nephrolithiasis. The survey, treatment, and follow-up of kidney diseases, acidic urine, and uric acid metabolism disorders should be considered in men with uric acid nephrolithiasis.

Evaluating factors that dictate struvite stone composition: A multi-institutional clinical experience from the EDGE Research Consortium

INTRODUCTION

Struvite stones account for 15% of urinary calculi and are typically associated with urease-producing urinary tract infections and carry significant morbidity. This study aims to characterize struvite stones based on purity of stone composition, bacterial speciation, risk factors, and clinical features.

METHODS

Retrospective data was collected from patients diagnosed with infection stones between 2008 and 2012. Stone analysis, perioperative urine cultures, bacterial speciation, and clinical data were collected and analyzed. The purity of struvite stones was determined. Statistical comparisons were made among homogeneous and heterogeneous struvite stones.

RESULTS

From the four participating centres, 121 struvite stones were identified. Only 13.2% (16/121) were homogenous struvite. Other components included calcium phosphate (42.1%), calcium oxalate (33.9%), calcium carbonate (27.3%), and uric acid (5.8%). Partial or full staghorn calculi occurred in 23.7% of cases. Urease-producing bacteria were only present in 30% of cases. Proteus, E. coli, and Enterococcus were the most common bacterial isolates from perioperative urine, and percutaneous nephrolithotomy was the most common modality of treatment. Only 40% of patients had a urinalysis that was nitrite-positive, indicating that urinalysis alone is not reliable for diagnosing infection stones. The study's limitation is its retrospective nature; as such, the optimal timing of cultures with respect to stone analysis or treatment was not always possible, urine cultures were often not congruent with stone cultures in the same patient, and our findings of E. coli commonly cultured does not suggest causation.

CONCLUSIONS

Struvite stones are most often heterogeneous in composition. Proteus remains a common bacterial isolate; however, E. coli and Enterococcus were also frequently identified. This new data provides evidence that patients with struvite stones can have urinary tract pathogens other than urease-producing bacteria, thus challenging previous conventional dogma.

Compositional analysis of various layers of upper urinary tract stones by infrared spectroscopy

The objective of the present study was to determine the composition of various layers of upper urinary stones and assess the mechanisms of stone nucleation and aggregation. A total of 40 integrated urinary tract stones with a diameter of >0.8 cm were removed from the patients. All of the stones were cut in half perpendicularly to the longitudinal axis. Samples were selected from nuclear, internal and external layers of each stone. Fourier transform infrared spectroscopy (FT-IR) was adopted for qualitative and quantitative analysis of all of the fragments and compositional differences among nuclear, internal and external layers of various types of stone were subsequently investigated. A total of 25 cases of calcium oxalate (CaOx) stones and 10 cases of calcium phosphate (CaP) stones were identified to be mixed stones, while 5 uric acid (UA) calculi were pure stones (purity, >95%). In addition, the contents of CaOx and carbapatite (CA.AP) crystals in various layers of the mixed stones were found to be variable. In CaOx stones, the content of CA.AP in nuclear layers was significantly higher than that of the outer layers (32.0 vs. 6.8%; P<0.05), while the content of CaOx was lower in the inner than in the outer layers (57.6 vs. 86.6%; P<0.05). In CaP stones, the content of CA.AP in the nuclear layers was higher than that in the outer layers (74.0 vs. 47.3%; P<0.05), while the content of CaOx was lower in the inner than in the outer layers (7.0 vs. 40.0%; P<0.05). The UA stones showed no significant differences in their composition among different layers. In conclusion, FT-IR analysis of various layers of human upper urinary tract stones revealed that CaOx and CaP stones showed differences in composition between their core and surface, while all of the UA calculi were pure stones. The composition showed a marked variation among different layers of the stones, indicating that metabolism has an important role in different phases of the evolution of stones. The present study provided novel insight into the pathogenesis of urinary tract stones and may contribute to their prevention and treatment.

Burden of Urolithiasis: Trends in Prevalence, Treatments, and Costs

CONTEXT

The recent evolution of management options for urolithiasis has presented a unique dilemma for the modern urologist. A comprehensive understanding of epidemiological trends along with current provider preferences in treating urinary stones would be beneficial.

OBJECTIVE

To review trends in the prevalence, treatments, and costs of urolithiasis worldwide.

EVIDENCE ACQUISITION

A literature review was performed using the MEDLINE database, the Cochrane Library Central search facility, Web of Science, and Google Scholar between 1986 and 2016. Keywords used for the search were "urolithiasis" and "prevalence; treatment; and cost".

EVIDENCE SYNTHESIS

The incidence and prevalence of urinary stones are rising around the world, including regions that have historically had low rates of urolithiasis. Common theories explaining this trend involve climate warming, dietary changes, and obesity. Shockwave lithotripsy (SWL) has been the preferred mode of treatment since its introduction in the 1980s. However, ureteroscopy (URS) has become increasingly popular for small stones regardless of location because of lower recurrence rates and costs. Developing countries have been slower to adopt URS technology and continue to use percutaneous nephrolithotomy at a steady rate.

CONCLUSIONS

URS has recently challenged SWL as the treatment modality preferred for small upper urinary tract stones. In some cases it is less expensive but still highly effective. As the burden of stone disease increases worldwide, appropriate selection of stone removal therapies will continue to play an important role and will thus require further investigation.

PATIENT SUMMARY

Urinary stones are becoming more prevalent. Recent advances in technology have improved the management of this disease and have decreased costs.

Prevalence of renal uric acid stones in the adult

The aim of this study was to estimate uric acid renal stone prevalence rates of adults in different countries of the world. PubMed was searched for papers dealing with "urinary calculi and prevalence or composition" for the period from January 1996 to June 2016. Alternative searches were made to collect further information on specific topics. The prevalence rate of uric acid stones was computed by the general renal stone prevalence rate and the frequency of uric acid stones in each country. After the initial search, 2180 papers were extracted. Out of them, 79 papers were selected after the reading of the titles and of the abstracts. For ten countries, papers relating to both the renal stone prevalence in the general population and the frequency of uric stones were available. Additional search produced 13 papers that completed information on 11 more countries in 5 continents. Estimated prevalence rate of uric acid stones was >0.75% in Thailand, Pakistan, Saudi Arabia, Iran, South Africa (white population), United States and Australia; ranged 0.50-0.75% in Turkey, Israel, Italy, India (Southern), Spain, Taiwan, Germany, Brazil; and <0.50% in Tunisia, China, Korea, Japan, Caribe, South Africa (blacks), India (Northern). Climate and diet are major determinants of uric acid stone formation. A hot and dry climate increases fluid losses reducing urinary volume and urinary pH. A diet rich in meat protein causes low urinary pH and increased uric acid excretion. On the other hand, uric acid stone formation is frequently associated with obesity, metabolic syndrome and diabetes type 2 that are linked to dietary energy excess mainly from carbohydrate and saturated fat and also present with low urine pH values. An epidemic of uric acid stone formation could be if current nutritional trends will be maintained both in developed countries and in developing countries and the areas of greater climatic risk for the formation of uric acid stones will enlarge as result of the "global warming".

Prevalence of kidney stones in mainland China: A systematic review

The data on the prevalence of kidney stones in mainland China are still lacking. We performed the present meta-analysis to assess the stone prevalence in mainland China from 1990 through 2016. A total of 18 articles were included. The pooled overall prevalence was 7.54% (95% CI, 5.94-9.15). The prevalence in age groups of <20 years, 20-29 years, 30-39 years, 40-49 years, 50-59 years, and 60 years and older was 0.27%, 3.15%, 5.96%, 8.18%, 9.14%, and 9.68%, respectively, showing that it increased with age. Moreover, the prevalence was 10.34% in males and 6.62% in females, with an odds ratio (OR) of 1.63 [95% CI: 1.51-1.76], indicating that males are more likely to suffer from this disease than females. However, urban areas (6.03%, 95% CI: 3.39-8.68) and rural areas (7.48%, 95% CI: 3.39-11.57) did not differ in the stone prevalence rate (OR = 0.84, 95% CI: 0.42-1.68). The prevalence in the year groups of 1991-2000, 2001-2010, and 2011 to date was 5.95%, 8.86%, and 10.63%, respectively, which indicated an increasing trend. Further high-quality surveys throughout mainland China are needed to confirm these findings.

Impact of dual energy characterization of urinary calculus on management

INTRODUCTION

Dual energy CT (DECT) is a recent technique that is increasingly being used to differentiate between calcium and uric acid urinary tract calculi. The aim of this study is to determine if urinary calculi composition analysis determined by DECT scanning results in a change of patient management.

METHOD

All patients presenting with symptoms of renal colic, who had not previously undergone DECT scanning underwent DECT KUB. DECT data of all patients between September 2013 and July 2015 were reviewed. Urinary calculi composition based on dual energy characterization was cross-matched with patient management and outcome.

RESULTS

A total of 585 DECT KUB were performed. 393/585 (67%) DECT scans revealed urinary tract calculi. After excluding those with isolated bladder or small asymptomatic renal stones, 303 patients were found to have symptomatic stone(s) as an explanation for their presentation. Of these 303 patients, there were 273 (90.1%) calcium calculi, 19 (6.3%) uric acid calculi and 11 (3.4%) mixed calculi. Of those with uric acid calculi, 15 were commenced on dissolution therapy. Twelve of those commenced on dissolution therapy had a successful outcome, avoiding need for surgical intervention (lithotripsy or stone retrieval). Three patients failed dissolution therapy and required operative intervention for definitive management of the stone.

CONCLUSION

Predicting urinary tract calculi composition by DECT plays an important role in identifying patients who may be managed with dissolution therapy. Identification of uric acid stone composition altered management in 15 of 303 (5.0%) patients, and was successful in 12, thereby avoiding surgery and its attendant risks.

Multivariate Analyses of Urinary Calculi Composition: A 13-Year Single-Center Study

BACKGROUND

The incidence and prevalence of urinary stone are increasing throughout the world. Compared to the past, recent demographics of patient with urolithiasis compositions are strikingly different. Furthermore, recent clinical studies implied that seasonal cyclicity might influence the distribution of stone composition.

METHODS

We sought to determine the trends in pathogenesis of urolithiasis based on urinary stone analyses. Between 2002 and 2014, a total of 2,383 eligible urinary stone samples from different patients were collected in our center. Infrared spectroscopy was used for urinary calculi analysis. A logistic regression analysis was used to investigate the relationship between urinary calculi composition and calendar month (season), gender, and age in north China during the past 13 years.

RESULTS

Calcium-containing calculi were the most frequent with an overall incidence of 84.1%. Calcium phosphate (CaP) or magnesium ammonium phosphate (MAP) stones were more frequent in females, while monohydrate calcium oxalate (COM), dihydrate calcium oxalate (COD), or uric acid (UA) stones were more common in males. Older individuals were associated with an increased risk of UA stones and a decreased risk of COD, CaP, or cystine stones. Additionally, from 2002 to 2014, the frequency of COD and MAP stone increased, whereas the trend of CaP, UA and cystine stones decreased. However, calendar month (season) was not significantly associated with differences in composition.

CONCLUSION

This study provides the present distribution of urolithiasis compositions in China. From 2002 to 2014, age and gender were significantly associated with stone composition, whereas calendar month was not.

Retrograde ureteric stent insertion in the management of infected obstructed kidneys

OBJECTIVES

To quantify the outcomes of retrograde ureteric stenting in the setting of infected hydronephrosis secondary to ureteric calculi.

PATIENTS AND METHODS

Prospective analysis of all patients over a 15-month period admitted with infected obstructed kidneys secondary to ureteric calculi. Inclusion criteria were based on clinical evidence of systemic inflammatory response syndrome (SIRS) and radiological evidence of obstructing ureteric calculi. Outcome measures included success of procedure, admission to intensive care unit (ICU), length of hospital stay, morbidity, and all-cause mortality during hospital admission.

RESULTS

In all, 52 patients were included. Success of retrograde ureteric stenting was 98%. In all, 17% of patients required an ICU admission, with a post ureteric instrumentation ICU admissions rate of 6%. The mean white cell count and serum creatinine improved significantly after the procedure. Major complication rate included septic shock 6%, but there were no episodes of major haemorrhage and no deaths.

CONCLUSION

Retrograde ureteric stenting is safe and effective in infected obstructed kidneys with results comparable to percutaneous nephrostomy tube insertion. Post instrumentation ICU admissions occur in 6% of retrograde stentings.

Renal struvite stones--pathogenesis, microbiology, and management strategies

Infection stones-which account for 10-15% of all urinary calculi-are thought to form in the presence of urease-producing bacteria. These calculi can cause significant morbidity and mortality if left untreated or treated inadequately; optimal treatment involves complete stone eradication in conjunction with antibiotic therapy. The three key principles of treating struvite stones are: removal of all stone fragments, the use of antibiotics to treat the infection, and prevention of recurrence. Several methods to remove stone fragments have been described in the literature, including the use of urease inhibitors, acidification therapy, dissolution therapy, extracorporeal shockwave lithotripsy, ureteroscopy, percutaneous nephrolithotomy (PCNL), and anatrophic nephrolithotomy. PCNL is considered to be the gold-standard approach to treating struvite calculi, but adjuncts might be used when deemed necessary. When selecting antibiotics to treat infection, it is necessary to acquire a stone culture or, at the very least, urine culture from the renal pelvis at time of surgery, as midstream urine cultures do not always reflect the causative organism.