Prevalence of urolithiasis in asymptomatic adults: objective determination using low dose noncontrast computerized tomography

Retrograde intrarenal surgery for asymptomatic incidental renal stones: a retrospective, real-world data analysis

OBJECTIVE

To determine surgical outcomes and stone-free rates (SFRs) when offering upfront retrograde intrarenal surgery (RIRS) to patients with asymptomatic incidental renal stones (AIRS), as active surveillance, shockwave lithotripsy or upfront intervention in patients with AIRS is still a debate among urologists.

PATIENTS AND METHODS

This retrospective FLEXible Ureteroscopy Outcomes Registry (FLEXOR), supported by the Team of Worldwide Endourological Researchers (TOWER), examines adult patients who underwent RIRS. We analysed a subset of asymptomatic patients with renal stones on imaging who were treated with RIRS. Data includes patient characteristics, stone specifications, anaesthesia type, perioperative details, complications, and SFR. A multivariable logistic regression analysis was performed to assess factors associated with the SFR.

RESULTS

Among 679 patients with AIRS, 640 met the inclusion criteria. The median age was 55 years, with 33.4% being female. In all, 22.1% had positive urine cultures. The median stone diameter was 12 mm, commonly in lower and interpolar locations. RIRS was preferentially performed under general anaesthesia using a reusable scope in 443 cases. Prophylactic antibiotics were administered to 314 patients. The median operation time was 58 min and the median laser time was 24 min. The SFR was 68.8%. The use of holmium laser (odds ratio [OR] 0.21, 95% confidence interval [CI] 0.06-0.63; P < 0.01) and multiple stones (OR 0.38, 95% CI 0.19-0.76; P < 0.01) were factors associated with lower odds of being stone free. Overall complications were minimal, with sepsis in 1.6% of patients. Re-interventions were performed in 76 cases (11.8%), with RIRS being the most common in 67 cases (10.6%).

CONCLUSION

Our multicentre real-world study is the first of its kind that highlights the pros and cons of offering RIRS to patients with AIRS and demonstrates a favourable SFR with acceptable complications. Pre-emptively discussing potential re-intervention helps patients make informed decisions, particularly in cases involving large and multiple stones.

Ex Vivo Surgical Removal Versus Conservative Management of Small Asymptomatic Kidney Stones in Living Donors and Long-term Kidney Transplant Outcomes

BACKGROUND

Donors with small asymptomatic kidney stones have been increasingly accepted because of organ shortages and advances in endoscopic urology. This study aims to evaluate and compare long-term living-donor kidney transplant outcomes following ex vivo surgical removal versus conservative management of donors' gifted asymptomatic stones.

METHODS

Between January 2007 and December 2021, 119 kidney transplant recipients received stone-bearing kidneys, divided into the removal group (N = 63) and observation group (N = 56). We evaluated posttransplant stone events, urinary infections, kidney function, delayed graft function, length of hospital stay, and survival outcomes.

RESULTS

After a median follow-up of 75.5 mo, the removal group had a 10.9% lower absolute incidence of stone events (7/56 [12.5%] versus 1/63 [1.6%]; hazard ratio, 0.08; 95% confidence interval, 0.01-0.77) and a 14.3% lower absolute incidence of urinary infections (16/56 [28.6%] versus 9/63 [14.3%]; hazard ratio, 0.42; 95% confidence interval, 0.19-0.95) than the observation group. The removal group also showed superior kidney graft function. The 2 groups had comparable length of hospital stay (11.0 versus 12.0 d; P = 0.297) and exhibited similar delayed graft function incidence (1/56 [1.8%] versus 2/63 [3.2%]; P = 1.000) and urinary stricture incidence (1/56 [1.8%] versus 3/63 [4.8%]; P = 0.621). Graft survival (P = 0.350) and patient survival (P = 0.260) were comparable between 2 groups. Subgroup analyses in recipients who received kidneys with stones <4 mm also reported similar results.

CONCLUSIONS

Ex vivo surgical removal might outperform conservative management for donors' gifted asymptomatic kidney stones, improving long-term transplant outcomes and reducing stone events without increasing perioperative complications, even for stones <4 mm.

Radiologic evaluation of the kidney transplant donor and recipient

The kidney is the most common solid organ transplant globally and rates continue to climb, driven by the increasing prevalence of end stage renal disease (ESRD). Compounded by advancements in surgical techniques and immunosuppression leading to longer graft survival, radiologists evermore commonly evaluate kidney transplant patients and candidates, underscoring their role along the transplant process. Multiphase computed tomography (CT) with multiplanar and 3D reformatting is the primary method for evaluating renal donor candidates, detailing renal size, vascular/collecting system anatomy, and identifying significant pathologies such as renal vascular diseases and nephrolithiasis. Ultrasound is the preferred initial postoperative imaging modality for graft evaluation due to its low cost, accessibility, noninvasiveness, and lack of radiation. CT and magnetic resonance imaging (MRI) may be useful adjunctive imaging techniques in diagnosing transplant pathology when ultrasound alone is not diagnostic. Kidney transplant complications are categorized by an approximate timeline framework, aiding in differential diagnosis based on onset, duration, and severity and include perinephric fluid collections, graft compression, iatrogenic injuries, vascular compromise, graft rejection, and neoplastic processes. This review discusses imaging strategies and important findings along the transplant timeline, from donor assessment to long-term recipient complications.

Prevalence and related factors of nephrolithiasis among medical staff in Qingdao, China: a retrospective cross-sectional study

BACKGROUND

Certain occupations may predispose individuals to urolithiasis, a multi-factorial disease. The study aimed to evaluate the prevalence and related factors of nephrolithiasis in medical staff in Qingdao, China.

METHODS

Physical examination results of 5115 in-service medical staff aged 22-60 years old were retrospectively analyzed. Multivariable logistic regression analysis and stratified analyses by age and gender were applied to explore the related factors of nephrolithiasis in these medical staff.

RESULTS

The overall nephrolithiasis prevalence in medical staff in Qingdao, China was 4.65%. Doctors were more prone to nephrolithiasis than nurses (5.63% vs. 3.96%, P = 0.013) and the peak prevalence (6.69%) was observed in medical staff working in the emergency department (ED). Male gender (OR = 1.615, 95% CI = 1.123-2.323, P = 0.010), overweight or obesity (OR = 1.674, 95% CI = 1.266-2.214, P < 0.001), work seniority ≥ 10 years (OR = 2.489, 95%CI = 1.675-3.699, P < 0.001) and working in the ED (OR = 1.815, 95% CI = 1.202-2.742, P = 0.005) were independent predictors for nephrolithiasis in medical staff based on the results of multivariate logistic regression analysis. The associations between overweight or obesity and nephrolithiasis risk as well as between work seniority ≥ 10 years and nephrolithiasis risk in medical staff were independent of age or gender in stratified analysis.

CONCLUSIONS

Nephrolithiasis prevalence in medical staff in Qingdao, China seemed not to be higher than that in the general population. Medical staff with work seniority ≥ 10 years and working in the ED should pay abundant attention to take measures to modify their nephrolithiasis risk.

The awareness of renal stones amongst Syrian refugees in northern Jordan

Kidney Stone Disease (KSD) is a globally prevalent condition that can be effectively addressed through proper education. This study investigated the awareness of kidney stones among refugees residing in northern Jordan. A questionnaire was administered to 487 refugees of diverse ages and socioeconomic backgrounds. Notably, 97.3% of the respondents had not attended university, and 30.8% held unskilled jobs. Upon familiarizing themselves with the signs and symptoms of kidney stones, 16.22% of men and 12.32% of women reported experiencing such symptoms. This revealed a significant association, suggesting that men might be more susceptible to developing kidney stones than women due to a lack of medical follow-up and examination for men in the camp. However, 38.77% of individuals were uncertain whether they had kidney stones. Furthermore, 38.96% of refugees were unsure about which healthcare professional to consult when experiencing kidney stone symptoms. This report highlights a serious issue with refugees' knowledge of the symptoms, causes, and treatments for kidney stones. The results indicate that Syrian refugees face challenges in acquiring adequate disease awareness, potentially related to issues of migration and war, including low levels of education, limited income, living in camps, and difficulties accessing treatments when needed. Implementing additional policies is necessary to address these challenges among Syrian refugees; however, further studies are needed to validate these findings.

Play it safe: renal function after bilateral flexible ureteroscopy for kidney stones

PURPOSE

We searched for perioperative renal function deterioration risk factors in patients that underwent bilateral flexible ureteroscopy (fURS) for kidney stones.

METHODS

From August 2016 to February 2020, symptomatic patients > 18 years old with bilateral kidney stones up to 20 mm in each side were prospectively studied. Serum creatinine samples were collected on admission to surgery, immediate postoperative (IPO), on POD 3, 10, and 30. Estimated glomerular filtration rate (eGFR) was calculated using Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI) without a race coefficient.

RESULTS

Thirty patients underwent bilateral fURS. Comparing to preoperative eGFR, median IPO and POD3 eGFR (p < 0.001) were significantly lower, and POD10 (p = 0.092) and POD30 (p = 0.648) were similar to preoperative eGFR. During follow-up, 22/30 (73.3%), 14/30 (46.7%), and 7/30 (23.3%) of the patients presented a decrease > 10% eGFR, > 20% eGFR, and > 30% eGFR, respectively. Multivariate analysis demonstrated that lower preoperative eGFR is a risk factor for eGFR < 60 mL/min/1.73 m2, p = 0.019 [1.021-1.263; 1.136]; ASA > 1 is a risk factor for decrease of eGFR > 10%, p = 0.028 [1.25-51.13; 8.00]; longer operative time is a risk factor for decrease of eGFR > 20%, p = 0.042 [1.00-1.05; 1.028]; and operative time ≥ 120 min is a risk factor for decrease of eGFR > 30%, p = 0.026 [0.016-0.773; 0.113].

CONCLUSIONS

Renal function suffers a reversible decrease after bilateral fURS. Our study suggests that adequate selection of patients and maintaining operative time < 120 min are relevant factors in preventing acute renal function deterioration following bilateral fURS.

Feasibility of Simultaneous Bilateral Endoscopic Surgery in Prone Split-Leg Position for Bilateral Upper Urinary Tract Calculi: A Pilot Study

INTRODUCTION

We explored the viability of simultaneous bilateral endoscopic surgery (SBES) in the prone split-leg position for managing bilateral calculi.

METHODS

We retrospectively reviewed 72 patients who underwent SBES, with procedures involving ureteroscopy (URS) and contralateral percutaneous nephrolithotomy (PNL) simultaneously, in prone split-leg position.

RESULTS

Operative times averaged 109.38 ± 30.76 min, with an average hospital stay of 7.79 ± 3.78 days. The bilateral stone-free rate (SFR) was 70.83%, while URS and PNL demonstrated comparable unilateral SFR (83.33% and 79.17%, respectively). Receiver operating characteristics curves for predicting unilateral residual fragments yielded an area under the curve of 0.84 (URS) and 0.81 (PNL) with respective cutoff values of stone diameter of 11.55 mm and 23.52 mm. Fifty-seven (79.17%) and 15 (20.83%) patients encountered grade 0-1/2 complications, with no severe complications (grade 3-5) recorded. No significant changes in blood count or renal function were observed post-SBES.

CONCLUSIONS

SBES in the prone split-leg position is a viable option for managing bilateral upper tract urolithiasis. Larger scale studies are needed to further assess safety and efficacy in various positions.

Longitudinal follow-up of incidental renal calculi on computed tomography

RATIONALE AND OBJECTIVES

Measuring small kidney stones on CT is a time-consuming task often neglected. Volumetric assessment provides a better measure of size than linear dimensions. Our objective is to analyze the growth rate and prognosis of incidental kidney stones in asymptomatic patients on CT.

MATERIALS AND METHODS

This retrospective study included 4266 scans from 2030 asymptomatic patients who underwent two or more nonenhanced CT scans for colorectal screening between 2004 and 2016. The DL software identified and measured the volume, location, and attenuation of 883 stones. The corresponding scans were manually evaluated, and patients without follow-up were excluded. At each follow-up, the stones were categorized as new, growing, persistent, or resolved. Stone size (volume and diameter), attenuation, and location were correlated with the outcome and growth rates of the stones.

RESULTS

The stone cohort comprised 407 scans from 189 (M: 124, F: 65, median age: 55.4 years) patients. The median number of stones per scan was 1 (IQR: [1, 2]). The median stone volume was 17.1 mm3 (IQR: [7.4, 43.6]) and the median peak attenuation was 308 HU (IQR: [204, 532]. The 189 initial scans contained 291stones; 91 (31.3%) resolved, 142 (48.8%) grew, and 58 (19.9) remained persistent at the first follow-up. At the second follow-up (for 27 patients with 2 follow-ups), 14/44 (31.8%) stones had resolved, 19/44 (43.2%) grew and 11/44 (25%) were persistent. The median growth rate of growing stones was 3.3 mm3/year, IQR: [1.4,7.4]. Size and attenuation had a moderate correlation (Spearman rho 0.53, P < .001 for volume, and 0.50 P < .001 for peak attenuation) with the growth rate. Growing and persistent stones had significantly greater maximum axial diameter (2.7 vs 2.3 mm, P =.047) and peak attenuation (300 vs 258 HU, P =.031) CONCLUSION: We report a 12.7% prevalence of incidental kidney stones in asymptomatic adults, of which about half grew during follow-up with a median growth rate of about 3.3 mm3/year.

Medial deviation of the ureter is a new sign that could predict stone impaction: a pilot study

OBJECTIVE

To assess the value medial deviation of the ureter at site of ureteric stone as a sign of ureteric stone impaction.

PATIENTS AND METHODS

All cases with medial deviation of the ureter at site of ureteric stones in our department over 4 years were enrolled in this pilot study. All cases were diagnosed with KUB and non-contrast CT (NCCT). Radiological and ureteroscopic findings were recorded.

RESULTS

A total of 32 patients with a single impacted stone in the proximal and middle third of the ureter were included in the study. Medial deviation of the ureter at the site of the stone was detected in the upper third of the ureter in 24 (75%) cases and in the middle third in 8 (25%) cases. There were mucosal polyps and mucosal erythema (inflammatory changes) seen by ureteroscopy in all cases (100%). Ureteroscopy was successfully completed with stone fragmentation in 23 (71.8%) patients: 8 of them needed ureteric catheter and 15 required JJ stent insertion. Failure of ureteroscopy with insertion of JJ stent was done in 5 (15.6%) patients. Removal of the stent and ureteroscopy was done after 4 weeks.

CONCLUSION

We conclude from this study that medial deviation of the ureter is a new reliable radiological sign of ureteric stone impaction.

Higher weight-adjusted waist index is associated with increased likelihood of kidney stones

Objectives

The objective of this study was to evaluate the association between weight-adjusted waist index (WWI) and the prevalence of kidney stones among adults in the United States.

Methods

The cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) spanning the years 2007-2018. A total of 31,344 participants were categorized into two groups: those with kidney stones and those without. WWI was determined by dividing waist circumference (cm) by the square root of body weight (kg). To examine the relationship between kidney stones and WWI, multivariate logistic regression models, smoothed curve fitting, and weighted generalized additive model (GAM) regression were employed. Subgroup analysis and interaction tests were conducted to explore the stability of this association across different groups.

Results

The final analysis comprised a total of 31,344 participants, including 2,928 individuals who had a history of kidney stones. In the fully adjusted model, an increase in WWI exhibited a positive correlation with the prevalence of kidney stones (OR=1.34, 95% CI: 1.18-1.51). When WWI was converted into quartiles (Q1-Q4), participants in the highest quartile (Q4) had a 69% greater risk of developing kidney stones compared to those in the lowest quartile (Q1) (OR=1.69, 95% CI: 1.28-2.25). This positive association was particularly notable among non-diabetic patients.

Conclusion

Our study demonstrates a significant positive association between weight-adjusted waist index levels and an elevated prevalence of kidney stones among US adults. Furthermore, this research highlights the potential utility of weight-adjusted waist index in the prevention of kidney stones in the overall population. This relationship is limited and further research is needed to test this hypothesis.

Residual fragment size following retrograde intrarenal surgery: a critical evaluation of related variables

Given the limited data on the predictive factors of residual kidney stone size after flexible ureteroscopy (fURS), this study aims to investigate the variables affecting residual stone size. The medical records of 642 patients without complications being treated for kidney stones with fURS between July 2014 and May 2022 were reviewed retrospectively, and the information of the 170 patients in whom residual stones were found was recorded. In addition to patient-specific factors and stone characteristics, length of postoperative hospital stay, postoperative fever, and preoperative antiaggregant use were evaluated. Of the 170 patients ultimately included in the study. The mean age was 51.56 (± 14.70). The mean stone size was 14.01 mm (± 5.75), the mean residual stone size was 7.04 mm (± 2.51), and the mean stone density was 829 Hounsfield units (± 395.06). The mean infundibulopelvic angle (IPA) was 49.37º (± 15.37), and 41.2% of the stones were non-opaque. The mean parenchymal thickness was 22.88 mm (± 5.55). 34 patients were on antiaggregant therapy. Preoperative stone size increases in stone density and decreases in IPA were found to be correlated with increase residual stone size (p < 0.001, p < 0.001, and p < 0.001, respectively). In addition, larger residual stones were observed after the fURS procedure in patients using anticoagulants and those without hydronephrosis (p = 0.02 and p = 0.016, respectively). Use of reliable predictive factors to forecast residual stone size after fURS may help to inform those treated and enable urologists to design rational surgical strategies.

Improving Outcomes of Same-sitting Bilateral Flexible Ureteroscopy for Renal Stones in Real-world Practice-Lessons Learnt from Global Multicenter Experience of 1250 Patients

Background

Bilateral kidney stones are commonly treated in staged procedures.

Objective

To evaluate outcomes after same-sitting bilateral retrograde intrarenal surgery (SSB-RIRS) for renal stones.

Design setting and participants

Data from adults who underwent bilateral RIRS in 21 centers were retrospectively reviewed (from January 2015 to June 2022). The inclusion criteria were unilateral/bilateral symptomatic bilateral stone(s) of any size/location in both kidneys and bilateral stones on follow-up with symptom/stone progression. Stone-free rate (SFR) was defined as absence of any fragment >3 mm at 3 mo.

Outcome measurements and statistical analysis

Continuous variables are presented as medians and 25-75th percentiles. A multivariable logistic regression analysis was performed to evaluate independent predictors of sepsis and bilateral SFR.

Results and limitations

A total of 1250 patients were included. The median age was 48.0 (36-61) yr. Of the patients, 58.2% were prestented. The median stone diameter was 10 mm on both sides. Multiple stones were present in 45.3% and 47.9% of the left and right kidneys, respectively. Surgery was stopped in 6.8% of cases. The median surgical time was 75.0 (55-90) min. Complications were transient fever (10.7%), fever/infection needing prolonged stay (5.5%), sepsis (2%), and blood transfusion (1.3%). Bilateral and unilateral SFRs were 73.0% and 17.4%, respectively. Female (odds ratio [OR] 2.97, 95% confidence interval [CI] 1.18-7.49, p = 0.02), no antibiotic prophylaxis (OR 5.99, 95% CI 2.28-15.73, p < 0.001), kidney anomalies (OR 5.91, 95% CI 1.96-17.94, p < 0.001), surgical time ≥100 min (OR 2.86, 95% CI 1.12-7.31, p = 0.03) were factors associated with sepsis. Female (OR 1.88, 95% CI 1.35-2.62, p < 0.001), bilateral prestenting (OR 2.16, 95% CI 1.16-7.66, p = 0.04), and the use of high-power holmium:YAG laser (OR 1.63, 95% CI 1.14-2.34, p < 0.01) and thulium fiber laser (OR 2.50, 95% CI 1.32-4.74, p < 0.01) were predictors of bilateral SFR. Limitations were retrospective study and no cost analysis.

Conclusions

SSB-RIRS is an effective treatment with an acceptable complication rate in selected patients with kidney stones.

Patient summary

In this large multicenter study, we looked at outcomes after same-sitting bilateral retrograde intrarenal surgery (SSB-RIRS) for renal stones in a large cohort. We found that SSB-RIRS was associated with acceptable morbidity and good stone clearance after a single session.

A comparison between asymptomatic and symptomatic ureteral stones

To investigate the characteristics and impact of asymptomatic (silent) ureteral stones on renal function and compare them with those of symptomatic stones. We retrospectively reviewed the medical records of 677 patients who underwent ureteroscopic lithotripsy or laparoscopic ureterolithotomy for ureteral stones between 2016 and 2020. Patients were divided into two groups according to the presence of recognizable symptoms. We investigated the characteristics and impact of silent stones on post-treatment renal function recovery and compared them with those of symptomatic stones. Among the 677 patients, 43 (6.4%) had asymptomatic ureteral stones, and 634 (93.6%) had symptomatic ureteral stones. Compared to symptomatic stones, asymptomatic stones were larger (11.4 mm vs. 9.6 mm, p = 0.003), more commonly present in the upper ureter (62.7% vs. 48.0%, p = 0.04), and more commonly associated with high-grade hydronephrosis (32.8% vs. 12.3%, p < 0.001); however, no difference in metabolite composition was observed between the two group of stone. In the asymptomatic stone group, the mean preoperative estimated glomerular filtration rate (eGFR) was 77.37 ± 23.54 mL/min/1.73 m², and the mean postoperative eGFR indicated no significant improvement at 1 day, 7 days, 3 months, and 12 months (76.66 ± 21.45, 77.89 ± 20.87, 77.29 ± 22.22, and 76.71 ± 24.21 mL/min/1.73 m², respectively; p = 0.567, p = 0.613, p = 0.924, and p = 0.202, respectively). In the symptomatic stone group, the mean preoperative eGFR was 78.17 ± 28.25 mL/min/1.73 m²; the mean postoperative eGFRs at 1 day, 7 days, 3 months, and 12 months were 81.24 ± 26.38, 86.16 ± 25.61, 89.11 ± 25.43, and 89.50 ± 26.01 mL/min/1.73 m², respectively and demonstrated significant improvement (p = 0.002, p < 0.001, p < 0.001, and p < 0.001, respectively). Silent stones irreversibly impaired renal function, even after proper management. Therefore, active treatment strategies are required for all patients who are hesitant to receive treatment for silent stones because of their asymptomatic status to prevent permanent renal impairment.

Duration of Follow-up and Timing of Discharge from Imaging Follow-up, in Adult Patients with Urolithiasis After Surgical or Medical Intervention: A Systematic Review and Meta-analysis from the European Association of Urology Guideline Panel on Urolithiasis

CONTEXT

No algorithm exists for structured follow-up of urolithiasis patients.

OBJECTIVE

To provide a discharge time point during follow-up of urolithiasis patients after treatment.

EVIDENCE ACQUISITION

We performed a systematic review of PubMed/Medline, EMBASE, Cochrane Library, clinicaltrials.gov, and reference lists according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Fifty studies were eligible.

EVIDENCE SYNTHESIS

From a pooled analysis of 5467 stone-free patients, we estimated that for a safety margin of 80% for remaining stone free, patients should be followed up using imaging, for at least 2 yr (radiopaque stones) or 3 yr (radiolucent stones) before being discharged. Patients should be discharged after 5 yr of no recurrence with a safety margin of 90%. Regarding residual disease, patients with fragments ≤4 mm could be offered surveillance up to 4 yr since intervention rates range between 17% and 29%, disease progression between 9% and 34%, and spontaneous passage between 21% and 34% at 49 mo. Patients with larger residual fragments should be offered further definitive intervention since intervention rates are high (24-100%). Insufficient data exist for high-risk patients, but the current literature dictates that patients who are adherent to targeted medical treatment seem to experience less stone growth or regrowth of residual fragments, and may be discharged after 36-48 mo of nonprogressive disease on imaging.

CONCLUSIONS

This systematic review and meta-analysis indicates that stone-free patients with radiopaque or radiolucent stones should be followed up to 2 or 3 yr, respectively. In patients with residual fragments ≤4 mm, surveillance or intervention can be advised according to patient preferences and characteristics, while for those with larger residual fragments, reintervention should be scheduled.

PATIENT SUMMARY

Here, we review the literature regarding follow-up of urolithiasis patients. Patients who have no stones after treatment should be seen up to 2-3 yr, those with large fragments should be reoperated, and those with small fragments could be offered surveillance with imaging.

The Role of Radiological Imaging in the Diagnosis and Treatment of Urolithiasis: A Narrative Review

The incidence and prevalence of urolithiasis have been increasing worldwide for the last several decades. This increase could be attributed to many factors, including missed cases of small stones, a sedentary lifestyle, a high BMI, a lack of physical activity, and poor dietary intake. In addition, the increased incidence of co-morbidities such as diabetes, dyslipidemia, infections, and multiple urinary tract surgeries could contribute significantly to the formation of urolithiasis. Radiology has a major role in diagnosing a variety of these stone types and can be used in planning management approaches, either as guidance or as a direct therapeutic method for stones. Because of the availability, safety, cost, and effectiveness of radiological imaging nowadays, urolithiasis is rarely missed; furthermore, the availability of radiological treatment options decreases the need for surgical intervention for urolithiasis, which minimizes hospital stay and surgical-related complications. This review aims to scope and analyze the role of radiological imaging modalities in reaching a diagnosis and planning treatment options for urolithiasis in different circumstances. Information was gathered from relevant peer-reviewed publications in PubMed and thereafter refined and summarized to provide a comprehensive review. The selected indexing terms included "radiological imaging modality," "treatment of urolithiasis," and "diagnosis of urolithiasis," among others.

Automated Assessment of Renal Calculi in Serial Computed Tomography Scans

An automated pipeline is developed for the serial assessment of renal calculi using computed tomography (CT) scans obtained at multiple time points. This retrospective study included 722 scans from 330 patients chosen from 8544 asymptomatic patients who underwent two or more CTC (CT colonography) or non-enhanced abdominal CT scans between 2004 and 2016 at a single medical center. A pre-trained deep learning (DL) model was used to segment the kidneys and the calculi on the CT scans at each time point. Based on the output of the DL, 330 patients were identified as having a stone candidate on at least one time point. Then, for every patient in this group, the kidneys from different time points were registered to each other, and the calculi present at multiple time points were matched to each other using proximity on the registered scans. The automated pipeline was validated by having a blinded radiologist assess the changes manually. New graph-based metrics are introduced in order to evaluate the performance of our pipeline. Our method shows high fidelity in tracking changes in renal calculi over multiple time points.

Removal of Small, Asymptomatic Kidney Stones and Incidence of Relapse

BACKGROUND

The benefits of removing small (≤6 mm), asymptomatic kidney stones endoscopically is unknown. Current guidelines leave such decisions to the urologist and the patient. A prospective study involving older, nonendoscopic technology and some retrospective studies favor observation. However, published data indicate that about half of small renal stones left in place at the time that larger stones were removed caused other symptomatic events within 5 years after surgery.

METHODS

We conducted a multicenter, randomized, controlled trial in which, during the endoscopic removal of ureteral or contralateral kidney stones, remaining small, asymptomatic stones were removed in 38 patients (treatment group) and were not removed in 35 patients (control group). The primary outcome was relapse as measured by future emergency department visits, surgeries, or growth of secondary stones.

RESULTS

After a mean follow-up of 4.2 years, the treatment group had a longer time to relapse than the control group (P<0.001 by log-rank test). The restricted mean (±SE) time to relapse was 75% longer in the treatment group than in the control group (1631.6±72.8 days vs. 934.2±121.8 days). The risk of relapse was 82% lower in the treatment group than the control group (hazard ratio, 0.18; 95% confidence interval, 0.07 to 0.44), with 16% of patients in the treatment group having a relapse as compared with 63% of those in the control group. Treatment added a median of 25.6 minutes (interquartile range, 18.5 to 35.2) to the surgery time. Five patients in the treatment group and four in the control group had emergency department visits within 2 weeks after surgery. Eight patients in the treatment group and 10 in the control group reported passing kidney stones.

CONCLUSIONS

The removal of small, asymptomatic kidney stones during surgery to remove ureteral or contralateral kidney stones resulted in a lower incidence of relapse than nonremoval and in a similar number of emergency department visits related to the surgery. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the Veterans Affairs Puget Sound Health Care System; ClinicalTrials.gov number, NCT02210650.).

Optimal Delivery of Follow-Up Care for the Prevention of Stone Recurrence in Urolithiasis Patients: Improving Outcomes

Urolithiasis is a common clinical condition with frequent recurrences. Advances in knowledge of pathophysiological mechanisms permit the categorization of patients to low and high risk for recurrence, with specific metabolic abnormalities diagnosed in the second category. Follow-up is essential for patients with urolithiasis and consists of both imaging and metabolic follow-up with urine studies. No formal guidelines or solid evidence currently exists regarding frequency and type of follow-up studies to be performed in each category. This review aims to summarize existing evidence regarding follow-up, in order to guide clinicians on how and when to follow-up urolithiasis patients according to existing clinical scenario.

A deep learning system for automated kidney stone detection and volumetric segmentation on noncontrast CT scans

PURPOSE

Early detection and size quantification of renal calculi are important for optimizing treatment and preventing severe kidney stone disease. Prior work has shown that volumetric measurements of kidney stones are more informative and reproducible than linear measurements. Deep learning-based systems that use abdominal noncontrast computed tomography (CT) scans may assist in detection and reduce workload by removing the need for manual stone volume measurement. Prior to this work, no such system had been developed for use on noisy low-dose CT or tested on a large-scale external dataset.

METHODS

We used a dataset of 91 CT colonography (CTC) scans with manually marked kidney stones combined with 89 CTC scans without kidney stones. To compare with a prior work half the data was used for training and half for testing. A set of CTC scans from 6185 patients from a separate institution with patient-level labels were used as an external validation set. A 3D U-Net model was employed to segment the kidneys, followed by gradient-based anisotropic denoising, thresholding, and region growing. A 13 layer convolutional neural network classifier was then applied to distinguish kidney stones from false positive regions.

RESULTS

The system achieved a sensitivity of 0.86 at 0.5 false positives per scan on a challenging test set of low-dose CT with many small stones, an improvement over an earlier work that obtained a sensitivity of 0.52. The stone volume measurements correlated well with manual measurements (r 2 = 0.95 $r^2 = 0.95$ ). For patient-level classification, the system achieved an area under the receiver-operating characteristic of 0.95 on an external validation set (sensitivity = 0.88, specificity = 0.91 at the Youden point). A common cause of false positives were small atherosclerotic plaques in the renal sinus that simulated kidney stones.

CONCLUSIONS

Our deep-learning-based system showed improvements over a previously developed system that did not use deep learning, with even higher performance on an external validation set.

Should we support prophylactic intervention for asymptomatic kidney stones? A retrospective cohort study with long-term follow-up

The purpose of this study was to evaluate the long-term outcomes of patients undergoing prophylactic intervention or active surveillance for asymptomatic kidney stones and identify factors influencing the outcomes. In this retrospective cohort study, we reviewed the medical records of patients with asymptomatic kidney stones in two institutes between November 2014 and November 2019. Standardized questions were asked via phone calls to supplement the outcomes. Pain, hydronephrosis, stone growth, serious infection, gross hematuria, and spontaneous passage were defined as stone-related events. Future intervention was also recorded to evaluate management. A total of 101 patients with 120 kidney units were enrolled in this study. The median follow-up time was 63 months. The patients were classified into the control group (79 cases) or exposure group (41 cases) according to whether they underwent prophylactic intervention before any stone-related events. Generally, the rates of stone-related events and future intervention were significantly different between the two groups (57.0 vs. 12.2%, p < 0.001; and 31.6 vs. 4.9%, p = 0.002, respectively). After applying stabilized inverse probability of treatment weighted, Cox regression suggested that patients who underwent prophylactic intervention were less likely to experience stone-related events and future intervention (HR = 0.175, and HR = 0.028, respectively). In conclusion, patients who underwent prophylactic intervention had a lower risk of stone-related events and future intervention, although they had some slight complications.

Decision-Making, Preference, and Treatment Choice for Asymptomatic Renal Stones-Balancing Benefit and Risk of Observation and Surgical Intervention: A Real-World Survey Using Social Media Platform

Introduction: The burden of kidney stone disease has risen, and several treatment options now exist. We wanted to evaluate the preference and treatment choices based on the information provided for management of hypothetical 8 and 15 mm renal stone, and factors that influenced their decision. Materials and Methods: An online questionnaire to investigate trends in decision-making for two hypothesized scenarios of asymptomatic kidney stones (8 and 15 mm) was formatted online in Microsoft Forms and posted on social media (Facebook) in Europe. The ethical approval was obtained from the University Ethics Committee, and data were collected from general public between September and November 2020. Results: A total of 476 participants of different age and background answered the survey with a male:female ratio of 1:2.7. The age groups were categorized as 18-25 years (n = 149), 26-49 years (n = 192), and 50+ years (n = 135). In the 8 mm scenario, 107 of the 476 participants (22.5%) chose observation, 249 (52.3%) chose extracorporeal shockwave lithotripsy (SWL) and 120 (25.2%) opted for ureteroscopy (URS). In the 15 mm scenario, 194 participants chose SWL treatment (40.8%), 216 (45.4%) URS, and 66 (13.9%) preferred percutaneous nephrolithotomy. The influencing factors were success rate, complication risk and invasiveness of the procedure. On comparison to 8 mm stone, while stent avoidance and activity limitation were considered less important with 15 mm stone (p < 0.001), complication rates were considered more important (p < 0.001). Conclusion: More than one treatment choice for kidney stones often exists and clinicians must take patient choice into account via an informed decision-making process. While some might accept a higher risk of invasiveness and complications for higher stone-free rate, others might have a more conservative approach to this. It is about time that urologists take patient priorities and concerns into account and perhaps use Patient Reported Outcome Measures in addition to clinical outcomes when comparing treatment success.

THE FUNCTIONAL STATE OF THE RENAL PARENCHYMA AFTER VARIOUS VIDEO ENDOSURGICAL METHODS OF TREATMENT OF PATIENTS WITH LARGE AND COMPLEX KIDNEY STONES

The work is based on the analysis of literature data devoted to the problem of preserving the functional state of the kidneys with various video endoscopic methods of surgical treatment of large and complex kidney stones. The purpose of the review is to highlight the likelihood of deterioration in the functional state of the kidneys in the postoperative period. A detailed analysis of postoperative outcomes in various minimally invasive methods of treatment of patients with large and complex kidney stones was carried out, with an overview of the possibility of using dynamic nephroscintigraphy as a method of objectively assessing the functional state of the kidneys.

Contemporary considerations in the management and treatment of lower pole stones

The presence of lower pole stones poses a unique challenge due to the anatomical considerations involved in their management and treatment. Considerable research has been performed to determine the optimal strategy when faced with this highly relevant clinical scenario. Standard options for management include observation, shock wave lithotripsy, retrograde intrarenal surgery, or percutaneous nephrolithotomy. Indeed, each approach confers a distinct set of risks and benefits, which must be placed into the context of patient preference and expected outcomes. The current state of practice reflects a combination of lessons learned from managing calculi not only in the lower pole, but also from other locations within the kidney as well.

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.

Role of conservative management of stones

Urinary tract stone disease is one of the most common pathologies of the modern era with a rising prevalence owing to incidentally detected renal stones from imaging for other reasons. Although there is consensus on active management of symptomatic and asymptomatic stones in high-risk patient groups, conservative management of stones is still controversial. We have reviewed the literature pertaining to conservative management of 3 groups of stones-asymptomatic calyceal stones, staghorn stones, and ureteric stones-and summarized the findings to provide guidance in the conservative management of stones. In the calyceal stone group, our review showed an average spontaneous stone passage rate of 18% (range, 8%-32%) and an average requirement for surgical intervention of 20% (range, 7%-40%), with 62% of patients remaining safely on surveillance over a mean time of 4 years. In the staghorn group, overall disease-specific mortality was noted to be 16% (range, 0%-30%) and chance of renal deterioration was 21% (range, 0%-34.5%), with a mean incidence of infection of 22%. In case of conservatively managed ureteric stones, the rate of spontaneous passage for stones smaller than 5 mm was 75%, compared with 62% for those larger than 5 mm. Based on the position in the ureter, spontaneous passage rates were 49%, 58%, and 68% for proximal, middle, and distal thirds, respectively. Conservative management may be recommended for asymptomatic patients and those who are deemed unfit for any procedures. However, careful patient selection and thorough counseling about the risks of conservative management could make it a suitable option for an appropriate subset of patients.

Performance of Dual-Source CT in Calculi Component Analysis: A Systematic Review and Meta-Analysis of 2151 Calculi

Objective:

To evaluate the performance of dual-source computed tomography (DSCT) in the component analysis of all types of calculi by doing a systematic review and meta-analysis.

Methods:

We searched MEDLINE, Embase, Scopus, and CNKI up to February 28, 2020, for in vivo studies investigating the performance of DSCT in the component analysis of calculi. We pooled the sensitivity, specificity, and areas under the summary receiver operating characteristic (AUROC) curves using a random-effect model in the meta-analysis. Publication bias was evaluated using Deek’s funnel plot asymmetry test.

Results:

This analysis included a total of 37 studies in 1840 patients with 2151 calculi (462 uric acid [UA], 1383 calcium oxalate [CaOx], 55 cystine [Cys], 197 hydroxyapatite [HA], and 54 struvite [SV]). Using DSCT, the pooled accuracy for diagnosing UA (sensitivity, 0.95; specificity, 0.99), CaOx (0.98; 0.93), Cys (0.99; 0.99), HA (0.91; 0.99), and SV (0.42; 0.98) was calculated, respectively. The AUROC value was 0.99, 0.99, 1.00, 0.99, and 0.93, respectively. The P values for publication bias test were .49, .70, .07, .04, and .19, respectively.

Conclusion:

Dual-source computed tomography has high sensitivity and specificity for the component analysis of UA, CaOx, Cys, and HA calculi in vivo. This tool may have the potential to replace the current analysis tool in vitro in diagnosing calculi.

The Prevalence of Incidentally Detected Urolithiasis in Subjects Undergoing Computerized Tomography

Background and objective

Urolithiasis is defined as the presence of calculi in the urinary tract. Multiple studies have shown that urinary tract stones are one of the most common incidental findings in medical imaging. These stones are potentially dangerous and can cause severe impairment to renal function if they remain undiagnosed for a long time. The objective of this study was to determine the prevalence of incidentally detected urolithiasis in patients undergoing abdominopelvic CT scans.

Materials and methods

A retrospective cross-sectional study was conducted, which involved 721 patients selected by consecutive non-randomized sampling. The study population included patients who underwent an abdominopelvic CT scan in the radiology department of a tertiary care hospital in Pakistan. Patients aged below 10 years and those above 90 years were excluded from the study. Patients undergoing kidney, ureter, and bladder (KUB) scan for urolithiasis-associated symptoms and those with already known urolithiasis were also excluded. The data were recorded in a predesigned pro forma and analyzed with SPSS Statistics version 20.00 (IBM, Armonk, NY).

Results

A total of 721 patients underwent an abdominopelvic CT scan during the six months from July to December in the radiology department of the hospital. Out of these, 336 (46.6%) were males, and 385 (53.4%) were females. Incidental stones were found in 20 of these patients. Among these 20 stone formers, 11 were males, and nine were females. Out of them, six had stones in the right kidney, eight in the left kidney, and four patients had bilateral stones. The remaining two patients had stones in their ureters. In most cases, stones were found in lower poles as compared to the mid pole and upper pole of the kidneys.

Conclusion

The prevalence of incidentally detected urolithiasis was found to be 2.8% in this study. Its frequency was much higher in males (3.27%) compared to females (2.33%). Most of the stones were found in the kidneys whereas no stone was detected in the urinary bladder.

Prospective Evaluation of Bilateral Retrograde Intrarenal Surgery: Is It Really Safe?

Introduction: The aim of this study was to prospectively compare the outcomes of bilateral same-session retrograde intrarenal surgery (BSS RIRS) with unilateral RIRS and to compare the outcomes of first with second operated kidneys in BSS RIRS. Subjects and Methods: Consecutive symptomatic adult patients with kidney stones up to 20 mm who accepted to be treated by RIRS were prospectively studied. Stone-free rate (SFR) was evaluated by non-contrast CT for each renal unit, and surgical complications were evaluated based on Clavien-Dindo classification. Results: SFR (73.9% vs 76.1%, p = 0.830) and hospitalization time (14.43 ± 18.81 hours vs 13.00 ± 4.89 hours, p = 0.564) were similar between unilateral and BSS RIRS groups, with less consumption of disposable devices in BSS RIRS (p = 0.017). Operative time was longer in BSS RIRS (61.24 ± 26.62 minutes vs 88.65 ± 33.19 minutes, p < 0.001). Bilateral group had significant more overall complications by Clavien-Dindo classification than unilateral (15.9% vs 39.9%, p = 0.030) and more emergency room (ER) visits (11.6% vs 34.8%, p = 0.026). Moreover, although both groups temporarily increased creatinine levels, it was significantly higher in bilateral RIRS (p = 0.019). First operated kidney outcomes were similar to second operated kidney outcomes of BSS RIRS. Conclusion: Although BSS RIRS had similar SFR and consumed less disposable devices, it had a higher overall complication rate, a higher frequency of ER visits, and higher creatinine levels during follow-up than unilateral RIRS. There is no significant outcome difference between first and second operated kidneys in BSS RIRS.

Prevalence and Trends in Kidney Stone Among Adults in the USA: Analyses of National Health and Nutrition Examination Survey 2007-2018 Data

BACKGROUND

The contemporary prevalence and trends of kidney stones are not clear.

OBJECTIVE

To evaluate the gender-specific prevalence and trends in kidney stones among the US population.

DESIGN, SETTING, AND PARTICIPANTS

Data on self-reported history of kidney stones from 34 749 participants aged ≥20 yr from the National Health and Nutrition Examination Survey (NHANES) were analyzed.

INTERVENTION

Six 2-yr study cycles (2007-2008 to 2017-2018) of nationally representative series of surveys evaluated the health status of the US population.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Weighted prevalence estimates of kidney stones and 95% confidence intervals (CIs) were calculated in each study cycle. Multivariable-adjusted logistic regression models were used to investigate the temporal trends.

RESULTS AND LIMITATIONS

In the 2017-2018 cycle, the prevalence of kidney stones was 10.9% (CI: 9.3-12.7) in men as compared with 9.5% (CI: 8-11.2) in women. The prevalence of kidney stones increased steadily from 6.5% in the 2007-2008 cycle to 9.4% in the 2017-2018 cycle (p_trend = 0.001) among women but not among men (p_trend = 0.1). These trends remained after adjusting for sociodemographic correlates in both genders. Sensitivity analyses further adjusting for dietary information held the same results in trends (men: p_trend = 0.15; women: p_trend = 0.001). Non-Hispanic white ethnicity, obesity, gout, history of two or more pregnancies, menopause, and using female hormones were associated with a higher prevalence of kidney stones. The main limitation is the cross-sectional design of the study.

CONCLUSIONS

Although kidney stones are more common in men than in women in the USA, the gender gap in kidney stone prevalence appears to be closing in the past decade. Kidney stones are consistently higher among non-Hispanic white and obese, and women who have had multiple pregnancies or have used female hormone therapy.

PATIENT SUMMARY

The prevalence of kidney stones remains higher in adult US men than in women, but the trend has been increasing only in women, closing the gender gap in kidney stone prevalence.

Nephrolithiasis in the Obese Patient

PURPOSE OF REVIEW

The link between metabolic syndrome (MetS)/obesity and kidney stone disease (KSD) has gained importance over recent years due to the increasing prevalence and healthcare burden worldwide. This review analyses the literature exploring the link between MetS/obesity and KSD and the impact that obesity has on KSD management.

RECENT FINDINGS

Metabolic syndrome has been shown to increase an individual's risk of developing kidney stone disease, with insulin resistance forming a core component of the pathophysiology. The body habitus of an individual also influences the type of intervention that is most appropriate, with flexible ureteroscopy increasingly being the preferred option in obese patients. It is important for urologists to consider the features of metabolic syndrome to effectively manage episodes of KSD in obese patients. In addition, better quality evidence is required to effectively compare different treatment options in this group of patients.

Long term follow up of kidney donors with asymptomatic renal stones

Patients with asymptomatic kidney stones have a high rate of progression to becoming symptomatic kidney stones when followed for several years. Small kidney stones are often found incidentally on imaging when evaluating patients for kidney donation, and there is a concern that after nephrectomy, the donor may become symptomatic and incur damage to the remaining kidney. We reviewed kidney donors at our institution with asymptomatic stones and surveyed them several years after donation to see if the stones became clinically active.

Kidney Stone Composition in Third-World Areas: What Kashgar Tells Us?

OBJECTIVE

To analyze urinary stone compositions in patients from Kashgar, China.

MATERIALS AND METHODS

We analyzed the components of urinary stones in 732 consecutive patients with urolithiasis admitted to the First and Second People's Hospital of Kashgar Prefecture, Xinjiang, from July 2014 to November 2016. The patients were divided into two groups by ages: group A, 0 to 18 years and group B, >18 years old. The distributions of various stone compositions were analyzed and correlated with the gender and age.

RESULTS

The mean age of group A was 3.90 ± 4.09 years and that of group B was 39.88 ± 16.40 years. The overall gender ratio (male:female) was 2.27:1. Ammonium acid urate (AAU) stone was the most frequent stone, male 35.83% and female 33.48%. Female patients were significantly more common than male patients in calcium apatite stone (p = 0.004). Of all 732 cases, patients younger than 18 years were more than patients older than 18 years (58.47% vs 41.53%). The majority of the patients (77.87%) had the stone located in the upper urinary tract. Two peak ages for both genders were noted in 1 to 3 years and 19 to 40 years group of the patients. In group of 1 to 3 years patients, male were more than female (37.60% vs 24.55%, p = 0.001), whereas in the group of 10 to 18 years patients, female were more than male (10.71% vs 4.13%). AAU was the predominant stone component in group <1 year (70. 5%, p < 0.01, as compared with other groups.). Uric acid stone was more prevalent in group >60 years (66.8%, p < 0.01) than in other groups. Patients in 1 to 3 years were in the peak age group of AAU stones in both the upper and lower urinary tract.

CONCLUSION

Most of the patients with urolithiasis diagnosed and treated in Kashgar are <18 years old, especially younger than 3 years old. The most frequent stone component in this area was AAU. More than 50% patients <18 years old had AAU stone. The mechanisms that could trigger the high prevalence of AAU stone in patients <18 years old are worth further investigation.

Eleven-year Cumulative Incidence and Estimated Lifetime Prevalence of Urolithiasis in Korea: a National Health Insurance Service-National Sample Cohort Based Study

BACKGROUND

The purpose of this study was estimation of the cumulative incidence and lifetime prevalence of urolithiasis in Korea.

METHODS

We used a National Health Insurance Service (NHIS) sample cohort dataset that included approximately 1 million individuals from Korea. Data from January 2002 to December 2013 were collected. We calculated the annual prevalence, recurrence rate, and estimate lifetime prevalence of urolithiasis. Multivariate logistic regression analysis was used to identify risk factors associated with urolithiasis.

RESULTS

There were 57,921 diagnosed urolithiasis cases in the NHIS database over the 11 years studied. The annual incidence of urolithiasis increased every year (Poisson regression; hazard ratio, 1.025; P < 0.001). Of the patients with urolithiasis, 21.3% experienced disease recurrence within 5 years. The 11-year cumulative incidence was 5.71%, and the incidence in men was higher than that seen in women (7.07% vs. 4.34%, respectively). The 11-year cumulative incidence in the 60- to 69-year-old group (9.08%) was higher than that seen in any other age group. The overall standardized lifetime prevalence rate was estimated to be 11.5%: 12.9% in men and 9.8% in women. Meanwhile, age (> 60 years), income level, diabetes, body mass index, hypertension, and cancer history were identified as contributing factors to urolithiasis.

CONCLUSION

This study demonstrates that the annual incidence of urolithiasis in Korea is increasing. The overall standardized lifetime prevalence rate was higher than that reported in a previous report. This study is significant in that it is the first retrospective cohort study to estimate the lifetime prevalence of urolithiasis using a large national retrospective cohort.

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.

Infant nephrolithiasis and nephrocalcinosis: Natural history and predictors of surgical intervention

INTRODUCTION

Renal stone disease diagnosed in the first year of life is relatively uncommon. While risk factors such as low birth weight, furosemide exposure, and metabolic disorders are well established, there exists little information regarding resolution rates and need for surgical intervention. Our study objective was to evaluate urolithiasis and renal calcification resolution rates, time to resolution, and need for surgical intervention in children diagnosed in their first year of life.

MATERIAL AND METHODS

REB approved retrospective chart review of children younger than 12 months of age (corrected for prematurity) diagnosed with nephrolithiasis and/or nephrocalcinosis in a tertiary pediatric hospital between April 2000 and August 2015 with a minimum 1-year follow-up period. Exact logistic regression was performed to assess the relationship between size of the largest stone (on either side) and the need for surgical intervention. Kaplan-Meier curves were constructed to examine time to stone resolution among those not requiring surgical intervention.

RESULTS

62 patients (61% male) were diagnosed with stones or nephrocalcinosis by ultrasound at a median age of 2.9 months. Of these, 37% had been admitted to the NICU because of prematurity, low birth weight or comorbidities. A total of 45 patients were found to have stones (Table); 35 of these had a stone at initial ultrasound and 10 initially diagnosed as nephrocalcinosis were later confirmed to have a stone. 67% of all stones were asymptomatic on presentation. Metabolic anomalies were present in 56% (35/62), and 16% (10/62) required medical treatment. Seven patients ultimately required surgical intervention. Stone size was found to predict the eventual need for surgical intervention (OR 3.52, 95% CI 1.47-12.78) for each 0.1 mm increase in diameter). Among patients not requiring surgical intervention (n = 38), the estimated median time to spontaneous resolution of urolithiasis was 1.1 years (95% CI 0.89-1.53, range 2 months-6 years) and 1.2 years for nephrocalcinosis (95% CI 0.59-2.13).

CONCLUSIONS

Spontaneous resolution was a common outcome for newborns and infants diagnosed with urolithiasis in the first year of life, but high variability in time-to-resolution was observed. Only a small proportion who had confirmed stones on ultrasound required surgical intervention (15%), and large stone size was a predictive factor for surgery.

Using Behavior Change Techniques to Guide Selections of Mobile Applications to Promote Fluid Consumption

OBJECTIVE

To determine the extent to which validated techniques for behavior change have been infused in commercially available fluid consumption applications (apps).

MATERIALS AND METHODS

Coders evaluated behavior change techniques represented in online descriptions for 50 fluid consumption apps and the latest version of each app.

RESULTS

Apps incorporated a limited range of behavior change techniques (<20% of taxonomy). The number of techniques varied by operating system but not as a function of whether apps were free or paid. Limitations include the lack of experimental evidence establishing the efficacy of these apps.

CONCLUSION

Patients with urolithiasis can choose from many apps to support the recommended increase in fluid intake. Apps for iOS devices incorporate more behavior change techniques compared to apps for the Android operating system. Free apps are likely to expose patients to a similar number of techniques as paid apps. Physicians and patients should screen app descriptions for features to promote self-monitoring and provide feedback on discrepancies between behavior and a fluid consumption goal.

Challenging Case: Stones

A 40-year-old woman presents to the emergency department after a motor vehicle accident, and a CT scan revealed no injuries but incidentally notes three non-obstructing stones in the left kidney of 3, 4, and 5 mm in size. She is completely asymptomatic and has no history of urolithiasis.