Posterior urethral valves in patients with trisomy 21: Similar renal outcomes and rates of volitional voiding

INTRODUCTION

Posterior urethral valves (PUV) occur in patients with Down Syndrome (DS) at a rate of 3-4%; far higher than the general population. Our understanding of the relationship between PUVs and DS is in its infancy, with the majority of the literature consisting of case reports. In this study, we present the largest known series of DS patients with PUVs.

AIM

We hypothesized that patients with DS and PUVs would have worse functional bladder outcomes and renal outcomes when compared to PUV patients without DS.

STUDY DESIGN

We queried our prospectively managed multi-institutional database of PUV patients from 1990 to 2021. We identified patients with a concomitant diagnosis of DS and PUV. In addition, we performed a systematic review of the literature describing the presentation of children with PUV and DS. Patient demographics, renal outcomes, voiding habits, surgical interventions, and radiologic images were aggregated and analyzed.

RESULTS

Out of the 537 patients in our PUV database, we identified 18 patients with a concomitant diagnosis of PUV and DS, as well as 14 patients with a concomitant diagnosis of PUV and DS from the literature. DS and non-DS patients had a similar age at presentation, 31.5 days (2-731) and 17 (4-846), and length of follow up 6.32 years (2-11.2) and 6.98 (1-13). Both groups had similar nadir creatinines DS 0.43 (0.4-0.8), non-DS 0.31 (0.2-0.5) and similar rates of renal failure (DS 11.1% and non-DS 14.5%). With respect to bladder outcomes, a similar percentage of patients were volitionally voiding at last follow up (DS 72.2% and non-DS 72.3%). Our literature review corroborated these findings.

CONCLUSIONS

Patients with DS and PUV have similar renal outcomes to other PUV patients in terms of renal function, progression to renal failure, and probability of volitional voiding with continence. Given the increased rate of PUVs in the DS population, physicians should have a high index of suspicion for PUV when patients with DS present with voiding dysfunction.

Assessing the Utility of Tamsulosin in Delaying Progression to Clean Intermittent Catheterization and End-stage Renal Disease in Patients With Posterior Urethral Valves: Are We Postponing the Inevitable?

OBJECTIVE

To assess whether tamsulosin may aid emptying of the lower urinary tract in posterior urethral valves patients, mitigating the likelihood of progressing to clean intermittent catheterization (CIC) or need for renal replacement therapy.

METHODS

We reviewed a prospective institutional database containing posterior urethral valves patients treated between January 2000 and January 2022. After assessing baseline characteristics, Kaplan-Meier survival curves and log-rank tests were generated to assess differences in clinically significant outcomes (progression to CIC, dialysis, or kidney transplantation) between those prescribed tamsulosin and those who were not.

RESULTS

A total of 179 patients were included. Fifty-nine patients received tamsulosin prior to initiation of CIC (group 1), and 120 did not (group 2). The baseline characteristics were similar between the two groups, except for anticholinergic use (tamsulosin group - 35/59 vs no tamsulosin - 32/120, P < .001). The median age at tamsulosin initiation was 26.0 months (IQR 15.5-48.6) and the median time from initiation of tamsulosin to progression to CIC was 52.6 months (IQR 10.1-69.3). Kaplan-Meier survival curves showed that patients on tamsulosin were less likely to progress to CIC (P = .021), however, there was no difference in progression to dialysis or kidney transplantation. A Cox-regression analysis controlling for baseline characteristics, including age, anticholinergic use, vesicoureteral reflux severity, and CKD stage at 1-year of life, showed a consistent effect of tamsulosin in delaying progression to CIC (HR 0.444 95%CI 0.218-0.902, P = .025).

CONCLUSION

While tamsulosin may delay CIC, it does not appear to delay progression to end-stage renal disease. Additional studies exploring specific patient factors are required to determine the timing and subset who may benefit the most from tamsulosin.

Mechanisms of the intestinal and urinary microbiome in kidney stone disease

Kidney stone disease affects ~10% of the global population and the incidence continues to rise owing to the associated global increase in the incidence of medical conditions associated with kidney stone disease including, for example, those comprising the metabolic syndrome. Considering that the intestinal microbiome has a substantial influence on host metabolism, that evidence has suggested that the intestinal microbiome might have a role in maintaining oxalate homeostasis and kidney stone disease is unsurprising. In addition, the discovery that urine is not sterile but, like other sites of the human body, harbours commensal bacterial species that collectively form a urinary microbiome, is an additional factor that might influence the induction of crystal formation and stone growth directly in the kidney. Collectively, the microbiomes of the host could influence kidney stone disease at multiple levels, including intestinal oxalate absorption and direct crystal formation in the kidneys.

Publication Trends in Pediatric Stone Disease: A Bibliometric Analysis

Introduction In the pediatric population, the prevalence of stone disease has increased in recent years. We aim to analyze the bibliometric characteristic of available literature on the management of stones in this population.

Methods We performed a search for articles published until December 2019 on the Scopus, Google Scholar, PubMed, Embase, and Web of Science databases using the keywords children, lithiasis, and stones. We excluded articles involving patients older than 18 years of age and those with non-urological lithiasis. Then, we performed a bibliometric analysis using the original language, year of publication, impact factor (yearly number of citations), and absolute citation count as variables to calculate the impact index (number of sources adjusted for the time since publication).

Results We included 291 articles published between 1940 and December 2019 for analysis. The average number of citations per manuscript was of 15.3 (± 21.9), and the average impact index was of 502 (± 976.4). A total of 4 articles were published before 1970. The evaluation of historical landmarks that could affect citation counts, such as the launch of a journal specialized in pediatric urology (Journal of Pediatric Urology), showed a mean citation count of 23.29 before the first edition, and of 14.96 after (p = 0.0006). The variation on the impact index with the same criteria was of 539.6 before the first edition of the Journal of Pediatric Urology, and of 316.32 after (p = 0.001). The average number of citations before internet access was of 17.9, and, after the internet, of 15.1 (p = 0.17). We also observed a difference in counts regarding languages of publication.

Conclusions The proportional academic productivity on pediatric stone disease demonstrates that citation counts do not reflect the true academic impact of subspecialized topics.

Posterior Urethral Valves Outcomes Prediction (PUVOP): a machine learning tool to predict clinically relevant outcomes in boys with posterior urethral valves

BACKGROUND

Early kidney and anatomic features may be predictive of future progression and need for additional procedures in patients with posterior urethral valve (PUV). The objective of this study was to use machine learning (ML) to predict clinically relevant outcomes in these patients.

METHODS

Patients diagnosed with PUV with kidney function measurements at our institution between 2000 and 2020 were included. Pertinent clinical measures were abstracted, including estimated glomerular filtration rate (eGFR) at each visit, initial vesicoureteral reflux grade, and renal dysplasia at presentation. ML models were developed to predict clinically relevant outcomes: progression in CKD stage, initiation of kidney replacement therapy (KRT), and need for clean-intermittent catheterization (CIC). Model performance was assessed by concordance index (c-index) and the model was externally validated.

RESULTS

A total of 103 patients were included with a median follow-up of 5.7 years. Of these patients, 26 (25%) had CKD progression, 18 (17%) required KRT, and 32 (31%) were prescribed CIC. Additionally, 22 patients were included for external validation. The ML model predicted CKD progression (c-index = 0.77; external C-index = 0.78), KRT (c-index = 0.95; external C-index = 0.89) and indicated CIC (c-index = 0.70; external C-index = 0.64), and all performed better than Cox proportional-hazards regression. The models have been packaged into a simple easy-to-use tool, available at https://share.streamlit.io/jcckwong/puvop/main/app.py CONCLUSION: ML-based approaches for predicting clinically relevant outcomes in PUV are feasible. Further validation is warranted, but this implementable model can act as a decision-making aid. A higher resolution version of the Graphical abstract is available as Supplementary information.

Comparative effectiveness of paediatric kidney stone surgery (the PKIDS trial): study protocol for a patient-centred pragmatic clinical trial

INTRODUCTION

The strength of the evidence base for the comparative effectiveness of three common surgical modalities for paediatric nephrolithiasis (ureteroscopy, shockwave lithotripsy and percutaneous nephrolithotomy) and its relevance to patients and caregivers are insufficient. We describe the methods and rationale for the Pediatric KIDney Stone (PKIDS) Care Improvement Network Trial with the aim to compare effectiveness of surgical modalities in paediatric nephrolithiasis based on stone clearance and lived patient experiences. This protocol serves as a patient-centred alternative to randomised controlled trials for interventions where clinical equipoise is lacking.

METHODS AND ANALYSIS

The PKIDS is a collaborative learning organisation composed of 26 hospitals that is conducting a prospective pragmatic clinical trial comparing the effectiveness of ureteroscopy, shockwave lithotripsy and percutaneous nephrolithotomy for youth aged 8-21 years with kidney and/or ureteral stones. Embedded within clinical care, the PKIDS trial will collect granular patient-level, surgeon-level and institution-level data, with a goal enrolment of 1290 participants over a 21-month period. The primary study outcome is stone clearance, defined as absence of a residual calculus of >4 mm on postoperative ultrasound. Secondary outcomes include patient-reported physical, emotional and social health outcomes (primarily using the Patient-Reported Outcome Measurement Information System), analgesic use and healthcare resource use. Timing and content of secondary outcomes assessments were set based on feedback from patient partners. Heterogeneity of treatment effect for stone clearance and patient-reported outcomes by participant and stone characteristics will be assessed.

ETHICS AND DISSEMINATION

This study is approved by the central institutional review board with reliance across participating sites. Participating stakeholders will review results and contribute to development dissemination at regional, national and international meetings.

TRIAL REGISTRATION NUMBER

NCT04285658; Pre-results.

Pre-natal vs Post-natal Presentation of PUV: A Multi-institutional Experience

OBJECTIVE

To compare the outcomes of prenatally versus postnatally diagnosed posterior urethral valves (PUV) at two large pediatric centres in North America to ascertain if the prenatal diagnosis of PUV is associated with better outcomes.

MATERIALS AND METHODS

All patients with PUV were identified at 2 large pediatric institutions in North America between 2000-2020 (The Hospital for Sick Children [SK] and Children's Hospital of Philadelphia [CHOP]). Baseline characteristics and outcome measures were compared between those diagnosed prenatally vs. postnatally. Main outcomes of interest included progression of chronic kidney disease (CKD), the need for renal replacement therapy (RRT) and bladder function compromise as determined by need for clean intermittent catheterization (CIC). Time-to-event analyses were completed when possible.

RESULTS

During the study period, 152 patients with PUV were treated at SK (39% prenatal) and 216 patients with PUV were treated at CHOP (71% prenatal). At SK, there was no difference between prenatal and postnatal groups in the proportion of patients who required RRT, progressed to CKD stage 3 and above, or who were managed with CIC when comparing the timing of diagnosis. The time to event for RRT and CIC was significantly younger for prenatally detected PUV. At CHOP, significantly more prenatal patients required RRT, however there was no significant difference in the age this outcome was reached. The proportion of children managed with CIC was not different but the time to event was significantly earlier in the prenatal group.

CONCLUSION

This study represents the largest multi-institutional series of patients with PUV and failed to identify any difference in the outcomes of prenatal versus postnatal detection of PUV. A multidisciplinary approach with standardization of the treatment pathways will help in understanding the true impact of prenatal/ early detection on outcomes of PUV.

Ultrasound-Based Renal Parenchymal Area and Kidney Function Decline in Infants With Congenital Anomalies of the Kidney and Urinary Tract

Congenital anomalies of the kidney and urinary tract are the leading cause of chronic kidney disease in children. Noninvasive imaging biomarkers that predict chronic kidney disease progression in early infancy are needed. We performed a pilot study nested in the prospective Chronic Kidney Disease in Children cohort study to determine the association between renal parenchymal area (RPA) on first post-natal renal ultrasound and change in estimated glomerular filtration rate (eGFR) in children with congenital anomalies of the kidney and urinary tract. Among 14 participants, 78.6% were males, the median age at the time of the ultrasound was 3.4 months (interquartile range, 1.3-7.9 mo), and the median total RPA z-score at baseline was -1.01 (interquartile range, -2.39 to 0.52). After a median follow-up period of 7.4 years (interquartile range, 6.8-8.2 y), the eGFR decreased from a median of 49.4 mL/min per 1.73 m² at baseline to 29.4 mL/min per 1.73 m², an annual eGFR percentage decrease of -4.68%. Lower RPA z-scores were correlated weakly with a higher annual decrease in eGFR (Spearman correlation, 0.35; 95% confidence interval, -0.25 to 0.76). This pilot study shows the feasibility of obtaining RPA from a routine ultrasound and suggests that a lower baseline RPA may be associated with a greater decrease in eGFR over time. Further studies with larger patient cohorts are needed to confirm this association.

Predictive accuracy of prenatal ultrasound findings for lower urinary tract obstruction: A systematic review and Bayesian meta-analysis

BACKGROUND

Lower urinary tract obstruction (LUTO) is a rare but critical fetal diagnosis. Different ultrasound markers have been reported with varying sensitivity and specificity.

AIMS

The objective of this systematic review and meta-analysis was to identify the diagnostic accuracy of ultrasound markers for LUTO.

MATERIALS AND METHODS

We performed a systematic literature review of studies reporting on fetuses with hydronephrosis or a prenatally suspected and/or postnatally confirmed diagnosis of LUTO. Bayesian bivariate random effects meta-analytic models were fitted, and we calculated posterior means and 95% credible intervals for the pooled diagnostic odds ratio (DOR).

RESULTS

A total of 36,189 studies were identified; 636 studies were available for full text review and a total of 42 studies were included in the Bayesian meta-analysis. Among the ultrasound signs assessed, megacystis (DOR 49.15, [15.28, 177.44]), bilateral hydroureteronephrosis (DOR 41.33, [13.36,164.83]), bladder thickening (DOR 13.73, [1.23, 115.20]), bilateral hydronephrosis (DOR 8.36 [3.17, 21.91]), male sex (DOR 8.08 [3.05, 22.82]), oligo- or anhydramnios (DOR 7.75 [4.23, 14.46]), and urinoma (DOR 7.47 [1.14, 33.18]) were found to be predictive of LUTO (Table 1). The predictive sensitivities and specificities however are low and wide study heterogeneity existed.

DISCUSSION

Classically, LUTO is suspected in the presence of prenatally detected megacystis with a dilated posterior urethra (i.e., the keyhole sign), and bilateral hydroureteronephrosis. However, keyhole sign has been found to have modest diagnostic performance in predicting the presence of LUTO in the literature which we confirmed in our analysis. The surprisingly low specificity may be influenced by several factors, including the degree of obstruction, and the diligence of the sonographer at searching for and documenting it during the scan. As a result, providers should consider this when establishing the differential for a fetus with hydronephrosis as the presence or absence of keyhole sign does not reliably rule in or rule out LUTO.

CONCLUSIONS

Megacystis, bilateral hydroureteronephrosis and bladder wall thickening are the most accurate predictors of LUTO. Given the significant consequences of a missed LUTO diagnosis, clinicians providing counselling for prenatal hydronephrosis should maintain a low threshold for considering LUTO as part of the differential diagnosis.

Financial incentives and wearable activity monitors to increase ambulation after cystectomy: A randomized controlled trial

OBJECTIVES

Financial incentive programs are effective in increasing physical activity for overweight, ambulatory adults. We sought to determine the potential effect size and direction of financial incentives on ambulation after radical cystectomy.

MATERIALS AND METHODS

We performed a pilot randomized controlled trial of daily financial incentives to meet postoperative step goals among adults with Eastern Cooperative Oncology Group performance status ≤2 who underwent radical cystectomy for bladder cancer at a single center. Step counts were measured over a 3- to 14-day preoperative period and 30-day postoperative period using a wearable activity monitor. Postoperative daily step goals of 10%, 25%, 40%, and 55% of mean preoperative daily step counts were set for postoperative weeks 1 through 4, respectively. The primary outcome was the number of postoperative days on which the step goals were met. Secondary outcomes included the number of daily postoperative steps taken and the length of stay. Participants randomized to the intervention arm received $1.50 for every day the goal was met with a 20% chance of a $100 reward if the step goal was met on >75% of the first 30 postoperative days. Questionnaires assessing self-reported physical activity, disability, and social support were administered preoperatively at 30 days postoperatively.

RESULTS

Thirty-three patients were analyzed, 11 in the control and 22 in the intervention arms. There were no statistically significant differences between incentive and control arms for the primary outcome (4.5/30 days vs. 9/30 days, P = 0.53). Results after adjusting for differences in baseline characteristics were similar (RR 1.00, 95% CI 0.24-4.19, P = 1.00). There were also no differences in average daily postoperative steps (median 979 vs. 1191, 95% CI -810 to 1,400, P = 0.59), length of stay (7.5 vs. 7, 95% CI -2.7 to 5.1, P = 0.56), or self-reported measures of disability, activity, and social support.

CONCLUSIONS

While this trial was a pilot study and not powered to detect a difference between groups, there was no suggestion of any clinically important impact of this financial incentive on postoperative ambulation. While a fully-powered trial is feasible, given the small range of plausible benefit, such a trial would be unlikely to influence clinical practice.

Standardization of microbiome studies for urolithiasis: an international consensus agreement

Numerous metagenome-wide association studies (MWAS) for urolithiasis have been published, leading to the discovery of potential interactions between the microbiome and urolithiasis. However, questions remain about the reproducibility, applicability and physiological relevance of these data owing to discrepancies in experimental technique and a lack of standardization in the field. One barrier to interpreting MWAS is that experimental biases can be introduced at every step of the experimental pipeline, including sample collection, preservation, storage, processing, sequencing, data analysis and validation. Thus, the introduction of standardized protocols that maintain the flexibility to achieve study-specific objectives is urgently required. To address this need, the first international consortium for microbiome in urinary stone disease - MICROCOSM - was created and consensus panel members were asked to participate in a consensus meeting to develop standardized protocols for microbiome studies if they had published an MWAS on urolithiasis. Study-specific protocols were revised until a consensus was reached. This consensus group generated standardized protocols, which are publicly available via a secure online server, for each step in the typical clinical microbiome-urolithiasis study pipeline. This standardization creates the benchmark for future studies to facilitate consistent interpretation of results and, collectively, to lead to effective interventions to prevent the onset of urolithiasis, and will also be useful for investigators interested in microbiome research in other urological diseases.

Association of Social Distancing, Population Density, and Temperature With the Instantaneous Reproduction Number of SARS-CoV-2 in Counties Across the United States

IMPORTANCE

Local variation in the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) across the United States has not been well studied.

OBJECTIVE

To examine the association of county-level factors with variation in the SARS-CoV-2 reproduction number over time.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included 211 counties, representing state capitals and cities with at least 100 000 residents and including 178 892 208 US residents, in 46 states and the District of Columbia between February 25, 2020, and April 23, 2020.

EXPOSURES

Social distancing, measured by percentage change in visits to nonessential businesses; population density; and daily wet-bulb temperatures.

MAIN OUTCOMES AND MEASURES

Instantaneous reproduction number (Rt), or cases generated by each incident case at a given time, estimated from daily case incidence data.

RESULTS

The 211 counties contained 178 892 208 of 326 289 971 US residents (54.8%). Median (interquartile range) population density was 1022.7 (471.2-1846.0) people per square mile. The mean (SD) peak reduction in visits to nonessential business between April 6 and April 19, as the country was sheltering in place, was 68.7% (7.9%). Median (interquartile range) daily wet-bulb temperatures were 7.5 (3.8-12.8) °C. Median (interquartile range) case incidence and fatality rates per 100 000 people were approximately 10 times higher for the top decile of densely populated counties (1185.2 [313.2-1891.2] cases; 43.7 [10.4-106.7] deaths) than for counties in the lowest density quartile (121.4 [87.8-175.4] cases; 4.2 [1.9-8.0] deaths). Mean (SD) Rt in the first 2 weeks was 5.7 (2.5) in the top decile compared with 3.1 (1.2) in the lowest quartile. In multivariable analysis, a 50% decrease in visits to nonessential businesses was associated with a 45% decrease in Rt (95% CI, 43%-49%). From a relative Rt at 0 °C of 2.13 (95% CI, 1.89-2.40), relative Rt decreased to a minimum as temperatures warmed to 11 °C, increased between 11 and 20 °C (1.61; 95% CI, 1.42-1.84) and then declined again at temperatures greater than 20 °C. With a 70% reduction in visits to nonessential business, 202 counties (95.7%) were estimated to fall below a threshold Rt of 1.0, including 17 of 21 counties (81.0%) in the top density decile and 52 of 53 counties (98.1%) in the lowest density quartile.2.

CONCLUSIONS AND RELEVANCE

In this cohort study, social distancing, lower population density, and temperate weather were associated with a decreased Rt for SARS-CoV-2 in counties across the United States. These associations could inform selective public policy planning in communities during the coronavirus disease 2019 pandemic.

Hydrate Philly: An Intervention to Increase Water Access and Appeal in Recreation Centers

Introduction

Previous interventions to increase water access and consumption have focused on school settings, have shown mixed results on sugar-sweetened beverage (SSB) consumption, and have rarely addressed tap water safety. Our randomized controlled trial examined how improving access and appeal of water in recreation centers in low-income neighborhoods affected counts of SSBs carried by youth attending summer camp.

Methods

Recreation centers (N = 28) matched on their characteristics were randomly assigned to control or intervention groups. Intervention centers received a new water fountain with a bottle filler (hydration station), water testing services, reusable water bottles, and water promotion and education training and materials. Primary outcomes were 1-year changes in center-level average daily gallons of water from fountains and hydration stations (flowmeter readings). Secondary outcomes were counts of SSBs observed, use of bottled water and reusable water bottles, staff SSB consumption, and hydration station maintenance.

Results

Results showed increased water use (b = 8.6, 95% CI, 4.2–13.0) and reusable bottle counts (b = 10.2, 95% CI, 4.2–16.1) in intervention centers compared with control centers. No change occurred in youth carrying SSBs at camp, but center staff’s past 30-day SSB consumption frequency decreased (b = −34.8, 95% CI, −67.7 to −1.9). Intervention sites had marginally lower odds of maintenance problems (OR = 0.09; 95% CI, 0.004–0.76, P = .06) than control sites.

Conclusion

Although providing hydration stations along with water testing, reusable water bottles, education, and promotion increased water consumption among youth at recreation centers, it had no effect on the number of SSBs observed during camp. Future strategies to increase water consumption should also address reducing SSB intake.

A randomized trial of a multi-level intervention to increase water access and appeal in community recreation centers

INTRODUCTION

Improving children's tap water intake and reducing sugar-sweetened beverage (SSB) consumption is beneficial for health and health equity, particularly in low-income communities and communities of color. Existing community level interventions to improve the intake of tap water have predominantly occurred in schools and have focused on promoting water consumption in cafeterias during lunch or snack periods.

METHODS

The "Hydrate Philly" intervention was developed to target multiple environmental and social factors to improve tap water consumption in community recreation centers in low-income communities: replacing old and unappealing water fountains with appealing water-bottle-filling "hydration stations", conducting water safety testing and publicizing results, disseminating reusable water bottles, promoting tap water, and discouraging SSB consumption. Efficacy of the intervention will be tested through a group-randomized controlled trial (n = 28 centers) of the intervention's impact on center-level water fountain/station use as measured by flow meters during a youth summer camp program primarily for children aged 6-12 years. Intervention impact on the primary outcome (use of drinking water sources) will be examined with a difference-in-differences approach using an ordinary least squares regression model for analysis at the center level. Secondary outcomes include SSBs brought to summer camp, reusable and single-use bottled water use, program trash, and recreation center staff SSB consumption.

DISCUSSION

Multilevel approaches are needed to increase tap water intake and decrease SSB consumption among low-income and minority youth beyond school and meal settings. The current study describes the Hydrate Philly intervention, the study design, and baseline characteristics of recreation centers participating in the study. ClinicalTrials.gov Registration: #NCT03637465.

A Dynamic Graph Cuts Method with Integrated Multiple Feature Maps for Segmenting Kidneys in 2D Ultrasound Images

RATIONALE AND OBJECTIVES

Automatic segmentation of kidneys in ultrasound (US) images remains a challenging task because of high speckle noise, low contrast, and large appearance variations of kidneys in US images. Because texture features may improve the US image segmentation performance, we propose a novel graph cuts method to segment kidney in US images by integrating image intensity information and texture feature maps.

MATERIALS AND METHODS

We develop a new graph cuts-based method to segment kidney US images by integrating original image intensity information and texture feature maps extracted using Gabor filters. To handle large appearance variation within kidney images and improve computational efficiency, we build a graph of image pixels close to kidney boundary instead of building a graph of the whole image. To make the kidney segmentation robust to weak boundaries, we adopt localized regional information to measure similarity between image pixels for computing edge weights to build the graph of image pixels. The localized graph is dynamically updated and the graph cuts-based segmentation iteratively progresses until convergence. Our method has been evaluated based on kidney US images of 85 subjects. The imaging data of 20 randomly selected subjects were used as training data to tune parameters of the image segmentation method, and the remaining data were used as testing data for validation.

RESULTS

Experiment results demonstrated that the proposed method obtained promising segmentation results for bilateral kidneys (average Dice index = 0.9446, average mean distance = 2.2551, average specificity = 0.9971, average accuracy = 0.9919), better than other methods under comparison (P < .05, paired Wilcoxon rank sum tests).

CONCLUSIONS

The proposed method achieved promising performance for segmenting kidneys in two-dimensional US images, better than segmentation methods built on any single channel of image information. This method will facilitate extraction of kidney characteristics that may predict important clinical outcomes such as progression of chronic kidney disease.

TRANSFER LEARNING FOR DIAGNOSIS OF CONGENITAL ABNORMALITIES OF THE KIDNEY AND URINARY TRACT IN CHILDREN BASED ON ULTRASOUND IMAGING DATA

Classification of ultrasound (US) kidney images for diagnosis of congenital abnormalities of the kidney and urinary tract (CAKUT) in children is a challenging task. It is desirable to improve existing pattern classification models that are built upon conventional image features. In this study, we propose a transfer learning-based method to extract imaging features from US kidney images in order to improve the CAKUT diagnosis in children. Particularly, a pre-trained deep learning model (imagenet-caffe-alex) is adopted for transfer learning-based feature extraction from 3-channel feature maps computed from US images, including original images, gradient features, and distanced transform features. Support vector machine classifiers are then built upon different sets of features, including the transfer learning features, conventional imaging features, and their combination. Experimental results have demonstrated that the combination of transfer learning features and conventional imaging features yielded the best classification performance for distinguishing CAKUT patients from normal controls based on their US kidney images.

Risk of fracture in urolithiasis: a population-based cohort study using the health improvement network

BACKGROUND AND OBJECTIVES

Studies have shown decreased bone mineral density in individuals with urolithiasis, but their burden of fracture remains unclear. This study sought to determine whether urolithiasis is associated with increased fracture risk across the lifespan and to delineate sex effects.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A population-based retrospective cohort study using The Health Improvement Network was performed. The median calendar year for the start of the observation period was 2004 (1994-2012). This study identified 51,785 participants with ≥1 of 87 diagnostic codes for urolithiasis and 517,267 randomly selected age-, sex-, and practice-matched participants. Cox regression was used to estimate the hazard ratio (HR) for first fracture. Fractures identified using diagnostic codes were classified by anatomic site.

RESULTS

Median age was 53 years, and 67% of participants were men, confirming their greater urolithiasis burden. Median time from urolithiasis diagnosis to fracture was 10 years. The HR for fracture associated with urolithiasis differed by sex and age (P for interactions, P≤0.003). In men, the adjusted HR was greatest in adolescence (1.55; 95% confidence interval [95% CI], 1.07 to 2.25) with an overall HR of 1.10 (95% CI, 1.05 to 1.16). Urolithiasis was associated with higher fracture risk in women aged 30-79 years (HR, 1.17-1.52), and was highest in women aged 30-39 years (HR, 1.52; 95% CI, 1.23 to 1.87). Peak background fracture rates were highest in boys aged 10-19 years and in women aged 70-79 years. The incidence per 10,000 person-years in participants with versus without urolithiasis was 392 versus 258 in male participants aged 10-19 years, and 263 versus 218 in women aged 70-79 years. Distribution of fracture site within sex did not differ between participants with versus without urolithiasis.

CONCLUSIONS

Urolithiasis was associated with higher incident fracture risk. The significantly higher risk at times of peak background fracture incidence in adolescent boys and elderly women has profound public health implications.

Smooth muscle differentiation and patterning in the urinary bladder

Smooth muscle differentiation and patterning is a fundamental process in urinary bladder development that involves a complex array of local environmental factors, epithelial-mesenchymal interaction, and signaling pathways. An epithelial signal is necessary to induce smooth muscle differentiation in the adjacent bladder mesenchyme. The bladder epithelium (urothelium) also influences the spatial organization of the bladder wall. Sonic hedgehog (Shh), which is expressed by the urothelium, promotes mesenchymal proliferation and induces differentiation of smooth muscle from embryonic bladder mesenchyme. Shh, whose signal is mediated through various transcription factors including Gli2 and BMP4, is likely also important in the patterning of bladder smooth muscle. However, it is not known to what extent early mediators of mesenchymal migration, other Shh-associated transcription factors, and crosstalk between the Shh signaling cascade and other pathways are involved in the patterning of bladder smooth muscle. Here we review the role of epithelial-mesenchymal interaction and Shh signaling in smooth muscle differentiation and patterning in the bladder. We also discuss emerging signaling molecules, transcription factors, and mesenchyme properties that might be fruitful areas of future research in the process of smooth muscle formation in the bladder.