Interobserver variability for interpretation of DMSA scans in the RIVUR trial

INTRODUCTION

Technetium-99m dimercaptosuccinic acid (DMSA) renal scans are used in the diagnosis of renal scarring. In the Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) trial that randomized 607 children, DMSA renal scans were used for evaluating the presence and the severity of renal scarring.

OBJECTIVE

The aim was to determine interobserver variability in reporting of DMSA renal scans in the RIVUR trial.

STUDY DESIGN

We compared DMSA renal scan reports for renal scarring and acute pyelonephritis from all non-reference local radiologists (ALRs) at study sites with adjudicated as well as non-adjudicated reports from two reference radiologists (RRs) of the RIVUR trial. Two-way comparisons of concordant and discrepant responses were analyzed using an unweighted kappa statistic between the ALR and the adjudicated RR interpretations. All analyses were performed using SAS v 9.4 (SAS institute 2015) and significance was determined at the 0.05 level.

RESULTS

Of the 2872 kidneys evaluated, adjudicated RR reports had 119 (4%) kidneys with renal scarring compared with 212 (7%) by the ALRs. For 79% kidneys the grading for scarring reported by ALRs was either upgraded (24%) or downgraded (55%) by RRs. For acute pyelonephritis (n = 2924), adjudicated RR reports had 85 (3%) kidneys with pyelonephritis compared with 151 (5%) by the ALRs. For 85% kidneys, the grading for pyelonephritis reported by the ALRs was either upgraded (28%) or downgraded (57%) by the RRs. A three-way comparison revealed that all three (RR1, RR2, and ALR) agreed over presence of renal scarring in 19% cases and two of the three agreed in 80% cases. The respective numbers for pyelonephritis were 13% and 84%. The agreement rate for all DMSA scan reports between the RRs and the ALRs was 93%.

DISCUSSION

The study revealed significant interobserver variability in the reporting of abnormal DMSA renal scans compared with the previously published studies. A noteworthy limitation was a lack of uniformity in local reporting of the scans.

CONCLUSIONS

Our study highlights the need for optimizing the clinical yield of DMSA renal scans by more specific guidelines, particularly for standardized and uniform interpretation.

Variation in the level of detail in pediatric voiding cystourethrogram reports

INTRODUCTION

Voiding cystourethrogram (VCUG) provides a wealth of data on urinary tract function and anatomy, but few standards exist for reporting VCUG findings.

OBJECTIVE

We aimed to assess variability in VCUG reports and to test our hypothesis that VCUG reports from pediatric facilities and pediatric radiologists are more complete than those performed at other facilities or by non-pediatric radiologists.

STUDY DESIGN

We analyzed original VCUG reports from children enrolled in the Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) trial. A 23-item checklist was created and used to evaluate reporting of technical (e.g. catheter size), anatomic (e.g. vesicoureteral reflux (VUR) presence and grade, bladder shape), and functional information (e.g. bladder emptying). Radiologists were classified as pediatric or non-pediatric radiologists. Facilities were categorized as to whether they were a free-standing pediatric hospital (FSPH), a pediatric "hospital within a hospital" (PHWH), a non-pediatric hospital (NPH), or an outpatient radiology facility (ORF). Multivariate linear regression was used to analyze factors associated with the completeness of the VCUG reports (percent of items reported from the 23-item checklist).

RESULTS

Six-hundred and two VCUGs were performed at 90 institutions. Of those, 76% were read by a pediatric radiologist, and 49% were performed at a FSPH (Table). On average, less than half of the 23 items in our standardized assessment tool were included in VCUG reports (mean 48%, SD 12). The completeness of reports varied by facility type: 51% complete at FSPH (SD 11), 50% at PHWH (SD 10), 36% at NPH (SD 11), and 43% at ORF (SD 8) (p < 0.0001). In multivariate analysis, VCUG reports generated at NPH or ORF had 8% fewer items included (95% CI 3.0-12.8, p < 0.01), and those generated at PHWH did not differ from those generated at FSPH. Reports read by a non-pediatric radiologist had 6% fewer items included (95% CI 3-9.7; p < 0.01) compared with those read by a pediatric radiologist.

DISCUSSION

There is substantial underreporting of findings in VCUG reports when assessing a widely represented sample of routine, community-generated reports using an idealized standard. Although VUR was often reported, other crucial anatomic and functional findings of the VCUG were consistently underreported across all facility types.

CONCLUSION

Although pediatric radiologist and pediatric hospitals generated more complete VCUG reports compared with those having non-pediatric origins, the differences are small when considering the substantial underreporting of VCUG findings in general. This underscores the opportunities for improvement in reporting of VCUG findings.

Antimicrobial Resistance and Urinary Tract Infection Recurrence

BACKGROUND

The Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) trial found that recurrent urinary tract infections (rUTI) with resistant organisms were more common in the trimethoprim-sulfamethoxazole prophylaxis (TSP) arm. We describe factors associated with trimethoprim-sulfamethoxazole (TMP-SMX) resistance of rUTIs in RIVUR.

METHODS

Children aged 2 to 71 months with first or second UTI (index UTI) and grade I to IV vesicoureteral reflux (VUR) were randomized to TSP or placebo and followed for 2 years. Factors associated with TMP-SMX-resistant rUTI were evaluated.

RESULTS

Among 571 included children, 48% were <12 months old, 43% had grade II VUR, and 38% had grade III VUR. Recurrent UTI occurred in 34 of 278 children receiving TSP versus 67 of 293 children receiving placebo. Among those with rUTI, 76% (26/34) of subjects receiving TSP had TMP-SMX-resistant organisms versus 28% (19/67) of subjects receiving placebo (P < .001). The proportion of TMP-SMX-resistant rUTI decreased over time: in the TSP arm, 96% were resistant during the initial 6 months versus 38% resistant during the final 6 months; corresponding proportions for the placebo arm were 32% and 11%. Among children receiving TSP, 7 (13%) of 55 with TMP-SMX-resistant index UTI had rUTI, whereas 27 (12%) of 223 with TMP-SMX-susceptible index UTI had rUTI (adjusted hazard ratio 1.38, 95% confidence interval 0.54-3.56). Corresponding proportions in placebo arm were 17 (26%) of 65 and 50 (22%) of 228 (adjusted hazard ratio 1.33, 95% confidence interval 0.74-2.38).

CONCLUSIONS

Although TMP-SMX resistance is more common among children treated with TSP versus placebo, resistance decreased over time. Among children treated with TSP, there was no significant difference in UTI recurrence between those with TMP-SMX-resistant index UTI versus TMP-SMX-susceptible UTI.

Predictors of Antimicrobial Resistance among Pathogens Causing Urinary Tract Infection in Children

OBJECTIVE

To determine which children with urinary tract infection are likely to have pathogens resistant to narrow-spectrum antimicrobials.

STUDY DESIGN

Children, 2-71 months of age (n = 769) enrolled in the Randomized Intervention for Children with Vesicoureteral Reflux or Careful Urinary Tract Infection Evaluation studies were included. We used logistic regression models to test the associations between demographic and clinical characteristics and resistance to narrow-spectrum antimicrobials.

RESULTS

Of the included patients, 91% were female and 76% had vesicoureteral reflux. The risk of resistance to narrow-spectrum antibiotics in uncircumcised males was approximately 3 times that of females (OR 3.1; 95% CI 1.4-6.7); in children with bladder bowel dysfunction, the risk was 2 times that of children with normal function (OR 2.2; 95% CI 1.2-4.1). Children who had received 1 course of antibiotics during the past 6 months also had higher odds of harboring resistant organisms (OR 1.6; 95% CI 1.1-2.3). Hispanic children had higher odds of harboring pathogens resistant to some narrow-spectrum antimicrobials.

CONCLUSIONS

Uncircumcised males, Hispanic children, children with bladder bowel dysfunction, and children who received 1 course of antibiotics in the past 6 months were more likely to have a urinary tract infection caused by pathogens resistant to 1 or more narrow-spectrum antimicrobials.

Renal Scarring in the Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) Trial

BACKGROUND AND OBJECTIVES

The main objectives of the Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) trial were to evaluate the role of antimicrobial prophylaxis in the prevention of recurrent urinary tract infection (UTI) and renal scarring in children with vesicoureteral reflux (VUR). We present a comprehensive evaluation of renal scarring outcomes in RIVUR trial participants.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This multicenter, randomized, placebo-controlled trial enrolled 607 children aged 2-71 months with grade 1-4 VUR diagnosed after a first or second febrile or symptomatic UTI. Study participants received trimethoprim-sulfamethoxazole or placebo and were followed for 2 years. Renal scarring was evaluated by baseline and follow-up (99m)technetium dimercaptosuccinic acid (DMSA) renal scans that were reviewed independently by two blinded reference radiologists.

RESULTS

At the end of the study, 58 (10%) of 599 children and 63 (5%) of 1197 renal units had renal scarring. New renal scarring did not differ between the prophylaxis and placebo groups (6% versus 7%, respectively). Children with renal scarring were significantly older (median age, 26 versus 11 months; P=0.01), had a second UTI before enrollment (odds ratio [OR], 2.85; 95% confidence interval [95% CI], 1.38 to 5.92), were more likely to be Hispanic (OR, 2.22; 95% CI, 1.13 to 4.34), and had higher grades of VUR (OR, 2.79; 95% CI, 1.56 to 5.0). The proportion of new scars in renal units with grade 4 VUR was significantly higher than in units with no VUR (OR, 24.2; 95% CI, 6.4 to 91.2).

CONCLUSIONS

Significantly more renal scarring was seen in relatively older children and in those with a second episode of febrile or symptomatic UTI before randomization. Preexisting and new renal scars occurred significantly more in renal units with grade 4 VUR than in those with low-grade or no VUR. Antimicrobial prophylaxis did not decrease the risk of renal scarring.

Antimicrobial prophylaxis for children with vesicoureteral reflux

BACKGROUND

Children with febrile urinary tract infection commonly have vesicoureteral reflux. Because trial results have been limited and inconsistent, the use of antimicrobial prophylaxis to prevent recurrences in children with reflux remains controversial.

METHODS

In this 2-year, multisite, randomized, placebo-controlled trial involving 607 children with vesicoureteral reflux that was diagnosed after a first or second febrile or symptomatic urinary tract infection, we evaluated the efficacy of trimethoprim-sulfamethoxazole prophylaxis in preventing recurrences (primary outcome). Secondary outcomes were renal scarring, treatment failure (a composite of recurrences and scarring), and antimicrobial resistance.

RESULTS

Recurrent urinary tract infection developed in 39 of 302 children who received prophylaxis as compared with 72 of 305 children who received placebo (relative risk, 0.55; 95% confidence interval [CI], 0.38 to 0.78). Prophylaxis reduced the risk of recurrences by 50% (hazard ratio, 0.50; 95% CI, 0.34 to 0.74) and was particularly effective in children whose index infection was febrile (hazard ratio, 0.41; 95% CI, 0.26 to 0.64) and in those with baseline bladder and bowel dysfunction (hazard ratio, 0.21; 95% CI, 0.08 to 0.58). The occurrence of renal scarring did not differ significantly between the prophylaxis and placebo groups (11.9% and 10.2%, respectively). Among 87 children with a first recurrence caused by Escherichia coli, the proportion of isolates that were resistant to trimethoprim-sulfamethoxazole was 63% in the prophylaxis group and 19% in the placebo group.

CONCLUSIONS

Among children with vesicoureteral reflux after urinary tract infection, antimicrobial prophylaxis was associated with a substantially reduced risk of recurrence but not of renal scarring. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; RIVUR ClinicalTrials.gov number, NCT00405704.).

Development and impact of an intervention to boost recruitment in a multicenter pediatric randomized clinical trial

OBJECTIVES

Our primary objective was to develop and evaluate an intervention to increase recruitment in a multicenter pediatric randomized clinical trial (RCT). Our secondary objective was to assess the impact beyond 120 days.

METHODS

The study was conducted at 17 academic centers participating in a pediatric RCT. The intervention consisted of utilizing a recruitment assessment tool at a site visit or teleconference with key site personnel.

RESULTS

We found a significant increase in the number of individuals enrolled for all 17 sites at 120 days postintervention (mean = 1.12 per site; median = 1 per site; 95% confidence interval = 1-2; P = .04). No significant differences were apparent beyond the first 120 days postintervention.

CONCLUSIONS

Successful recruitment in RCTs is essential to the quality, generalizability, and cost-effectiveness of clinical research. Implementation of this recruitment intervention may effectively increase recruitment in RCTs. Beyond the first 120 days postintervention, repeated interventions may be required. What is new? Despite general and pediatric-specific challenges to recruitment in RCTs, a paucity of evidence exists on effective recruitment strategies or assessment tools to reliably enhance recruitment. We developed a recruitment intervention for use in RCTs that enables clinical researchers to enhance recruitment.

Childhood vesicoureteral reflux studies: registries and repositories sources and nosology

Despite several recent studies, the advisability of antimicrobial prophylaxis and certain imaging studies for urinary tract infections (UTIs) remains controversial. The role of vesicoureteral reflux (VUR) on the severity and re-infection rates for UTIs is also difficult to assess. Registries and repositories of data and biomaterials from clinical studies in children with VUR are valuable. Disease registries are collections of secondary data related to patients with a specific diagnosis, condition or procedure. Registries differ from indices in that they contain more extensive data. A research repository is an entity that receives, stores, processes and/or disseminates specimens (or other materials) as needed. It encompasses the physical location as well as the full range of activities associated with its operation. It may also be referred to as a biorepository. This report provides information about some current registries and repositories that include data and samples from children with VUR. It also describes the heterogeneous nature of the subjects, as some registries and repositories include only data or samples from patients with primary reflux while others also include those from patients with syndromic or secondary reflux.

The RIVUR trial: profile and baseline clinical associations of children with vesicoureteral reflux

BACKGROUND AND OBJECTIVE

Vesicoureteral reflux (VUR) is diagnosed in ∼30% to 40% of children who have imaging studies after urinary tract infections (UTIs). Our goal is to characterize children enrolled in the Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) trial and to compare our study cohort with those from previously published studies.

METHODS

RIVUR investigators from 19 pediatric sites in the United States recruited 607 children with grade I through IV VUR. Children were enrolled after a first or second UTI. This cross-sectional report of baseline data includes extensive clinical, parental report, and imaging study results.

RESULTS

RIVUR recruited 607 children (558 girls, 49 boys) with grade I (11%), II (42%), III (38%), or IV (8%) reflux. The median age was 12 months, and most children (91%) were enrolled after their first UTI. The UTI leading to enrollment was both febrile and symptomatic for 323 children, febrile only in 197 children, and symptomatic only in 86. Renal involvement at baseline as documented by a (99m)Tc dimercaptosuccinic acid scan was uncommon with cortical defects identified in 89 (15%) children. Bladder and bowel dysfunction was identified in 71 (56%) of 126 toilet-trained subjects assessed.

CONCLUSIONS

RIVUR is the largest prospective, randomized trial for children with primary VUR to date, comparing prophylaxis with placebo. The study sample comprises patients from 19 pediatric clinical sites in the United States, whose demographic and clinical characteristics may differ from those of children enrolled in previous trials from other countries.

Factors that influence parental decisions to participate in clinical research: consenters vs nonconsenters

IMPORTANCE

A child's health, positive perceptions of the research team and consent process, and altruistic motives play significant roles in the decision-making process for parents who consent for their child to enroll in clinical research. This study identified that nonconsenting parents were better educated, had private insurance, showed lower levels of altruism, and less understanding of study design.

OBJECTIVE

To determine the factors associated with parental consent for their child's participation in a randomized, placebo-controlled trial.

DESIGN

Cross-sectional survey conducted from July 2008 to May 2011. The survey was an ancillary study to the Randomized Intervention for Children with VesicoUreteral Reflux Study.

SETTING

Seven children's hospitals participating in a randomized trial evaluating management of children with vesicoureteral reflux.

PARTICIPANTS

Parents asked to provide consent for their child's participation in the randomized trial were invited to complete an anonymous online survey about factors influencing their decision. A total of 120 of the 271 (44%) invited completed the survey; 58 of 125 (46%) who had provided consent and 62 of 144 (43%) who had declined consent completed the survey.

MAIN OUTCOMES AND MEASURES

A 60-question survey examining child, parent, and study characteristics; parental perception of the study; understanding of the design; external influences; and decision-making process. RESULTS Having graduated from college and private health insurance were associated with a lower likelihood of providing consent. Parents who perceived the trial as having a low degree of risk, resulting in greater benefit to their child and other children, causing little interference with standard care, or exhibiting potential for enhanced care, or who perceived the researcher as professional were significantly more likely to consent to participate. Higher levels of understanding of the randomization process, blinding, and right to withdraw were significantly positively associated with consent to participate. CONCLUSIONS AND RELEVANCE Parents who declined consent had a relatively higher socioeconomic status, had more anxiety about their decision, and found it harder to make their decision compared with consenting parents, who had higher levels of trust and altruism, perceived the potential for enhanced care, reflected better understanding of randomization, and exhibited low decisional uncertainty. Consideration of the factors included in the conceptual model should enhance the quality of the informed consent process and improve participation in pediatric clinical trials.

Rickets: Part I

Rickets is characterized by impaired mineralization and ossification of the growth plates of growing children caused by a variety of disorders, the most frequent of which is nutritional deficiency of vitamin D. Despite ample knowledge of its etiology and the availability of cost-effective methods of preventing it, vitamin D deficiency rickets remains a significant problem in developing and developed countries. This two-part review covers the history, etiology, pathophysiology and clinical and radiographical findings of vitamin D deficiency rickets. Other less frequent causes of rickets and some of the disorders entering into the differential diagnoses of rickets are also considered. Controversial issues surrounding vitamin D deficiency include determination of what constitutes vitamin D sufficiency and the potential relationship between low levels of vitamin D metabolites in many individuals and unexplained fractures in infants.

The RIVUR voiding cystourethrogram pilot study: experience with radiologic reading concordance

PURPOSE

Two reference radiologists independently review voiding cystourethrograms for the National Institutes of Health sponsored RIVUR (Randomized Intervention for Children with Vesicoureteral Reflux) trial for children with vesicoureteral reflux. A pilot study was required from all clinical centers before enrolling patients.

MATERIALS AND METHODS

Digital images were reviewed. Responses were compared and discrepancies adjudicated by teleconference to a final assessment.

RESULTS

A total of 75 studies from 19 sites were reviewed. Discrepancies in vesicoureteral reflux grade level were noted on the left and right side in 11 (15%, kappa 0.85) and 12 (16%, kappa 0.83) ureters, respectively. Other areas of disagreement were the presence of paraureteral diverticulum (left 11%, kappa 0.31; right 9%, kappa 0.34), urethral anatomy (15%, kappa 0.33), whether the child voided (8%, kappa 0.21), the presence of ureteral duplication (left 7%, kappa 0.64; right 3%, kappa 0.78) and the presence of bladder trabeculation (5%, kappa 0.32). Of 83 ureters in which reflux was seen there was grade disagreement about 23 (28%). Of 61 ureters initially assessed as grade II or III reflux by both readers, there was disagreement on 9 (15%). Of these 9 discrepancies 7 (78%) were adjudicated to the higher grade (grade III).

CONCLUSIONS

Discrepancies in the assessment of intermediate grade vesicoureteral reflux were noteworthy. Recommendations for patients with grade II or III reflux advanced by studies which rely on a single reading, which categorize only grade III or higher reflux as significant, may not be valid.

Theobald palm and his remarkable observation: how the sunshine vitamin came to be recognized

The seminal discovery that sunlight was important in the prevention of nutritional rickets was made in 1890 by Theobald A. Palm, a medical missionary who contrasted the prevalence of rickets in northern European urban areas with similar areas in Japan and other tropical countries. He surmised that exposure to sunlight prevented rickets. Over the next 40 years his observation led to an understanding of ultraviolet irradiation and its role in vitamin D synthesis. This opened a new era of appreciation for the curative powers of the sun and "the sunshine vitamin". While Palm's observations were in some ways obscure, they had a potent effect on the development of photobiology.

Post-streptococcal acute glomerulonephritis in children: clinical features and pathogenesis

Post-streptococcal acute glomerulonephritis (PSAGN) is one of the most important and intriguing conditions in the discipline of pediatric nephrology. Although the eventual outcome is excellent in most cases, PSAGN remains an important cause of acute renal failure and hospitalization for children in both developed and underdeveloped areas. The purpose of this review is to describe both the typical and less common clinical features of PSAGN, to outline the changes in the epidemiology of PSAGN over the past 50 years, and to explore studies on the pathogenesis of the condition with an emphasis on the search for the elusive nephritogenic antigen.

Milk composition in free-ranging polar bears (Ursus maritimus) as a model for captive rearing milk formula

The goals of this study were to have an improved understanding of milk composition and to help create a suitable milk formula for cubs raised in captivity. Milk samples were evaluated for fat, fatty acids, carbohydrate, vitamin D(3), 25(OH)D(3), vitamin A (retinol), vitamin E (α-tocopherol), protein, and amino acids. Total lipids in milk did not differ for cubs (mean ± SEM = 26.60 ± 1.88 g/100 ml vs. yearlings 27.80 ± 2.20 g/100 ml). Milk lipids were of 23.6% saturated fatty acid for cubs and 22.4% for yearlings. Milk consumed by cubs and yearlings contained 43.8 and 42.0% mono-unsaturated fatty acids and 23.4 and 21.9% polyunsaturated fatty acids, respectively. Carbohydrate content was higher in milk for cubs (4.60 ± 0.64 g/100 ml) than for yearlings (2.60 ± 0.40 g/100 ml). Vitamin D(3) concentration of milk was 18.40 ± 5.00 ng/ml in early lactation compared with 7.60 ± 2.00 ng/ml for mid-lactation. 25(OH)D(3) was lower in milk consumed by cubs (162.00 ± 6.70 pg/ml) than in milk consumed by yearlings (205.00 ± 45.70 pg/ml). Vitamin A concentrations were 0.06 ± 0.01 and 0.03 ± 0.01 µg/ml for cubs and yearlings, respectively. Vitamin E was higher in milk consumed by cubs (20.16 ± 4.46 µg/ml) than by yearlings (7.30 ± 1.50 µg/ml). Protein content did not differ in milk available to cubs (11.40 ± 0.80 g/100 ml compared with milk for yearlings 11.80 ± 0.40 g/100 ml). Taurine was the most abundant free amino acid at 3,165.90 ± 192.90 nmol/ml (0.04% as fed basis).

Metabolic bone disease in lion cubs at the London Zoo in 1889: the original animal model of rickets

In 1889 Dr. John Bland-Sutton, a prominent London surgeon, was consulted about fatal rickets in over 20 successive litters of lion cubs born at the London Zoo. He evaluated the diet and found the cause of rickets to be nutritional in origin. He recommended that goat meat with crushed bones and cod-liver oil be added to the lean horsemeat diet of the cubs and their mothers. Rickets were reversed, the cubs survived, and subsequent litters thrived. Thirty years later, in classic controlled studies conducted in puppies and young rats, the definitive role of calcium, phosphate and vitamin D in prevention and therapy of rickets was elucidated. Further studies led to identifying the structural features of vitamin D.Although the Bland-Sutton diet provided calcium and phosphate from bones and vitamins A and D from cod-liver oil, some other benefits of this diet were not recognized. Taurine-conjugated bile salts, necessary for intestinal absorption of fat-soluble vitamins, were provided in the oil cold-pressed from cod liver. Unlike canine and rodent species, felines are unable to synthesize taurine, yet conjugate bile acids exclusively with taurine; hence, it must be provided in the diet. The now famous Bland-Sutton "experiment of nature," fatal rickets in lion cubs, was cured by addition of minerals and vitamin D. Taurine-conjugated bile salts undoubtedly permitted absorption of vitamins A and D, thus preventing the occurrence of metabolic bone disease and rickets.

Taurine and the renal system

Taurine participates in a number of different physiologic and biologic processes in the kidney, often reflected by urinary excretion patterns. The kidney is key to aspects of taurine body pool size and homeostasis. This review will examine the renal-taurine interactions relative to ion reabsorption; renal blood flow and renal vascular endothelial function; antioxidant properties, especially in the glomerulus; and the role of taurine in ischemia and reperfusion injury. In addition, taurine plays a role in the renal cell cycle and apoptosis, and functions as an osmolyte during the stress response. The role of the kidney in adaptation to variations in dietary taurine intake and the regulation of taurine body pool size are described. Finally, the protective function of taurine against several kidney diseases is reviewed.

Functional TauT protects against acute kidney injury

Nephrotoxicity is common with the use of the chemotherapeutic agent cisplatin, but the cellular mechanisms that modulate the extent of injury are unknown. Cisplatin downregulates expression of the taurine transporter gene (TauT) in LLC-PK1 proximal tubular renal cells, and forced overexpression of TauT protects against cisplatin-induced apoptosis in vitro. Because the S3 segments of proximal tubules are the sites of both cisplatin-induced injury and adaptive regulation of the taurine transporter, we hypothesized that TauT functions as an anti-apoptotic gene and protects renal cells from cisplatin-induced nephrotoxicity in vivo. Here, we studied the regulation of TauT in cisplatin nephrotoxicity in a human embryonic kidney cell line and in LLC-PK1 cells, as well as in TauT transgenic mice. Cisplatin-induced activation of p53 repressed TauT and overexpression of TauT prevented the progression of cisplatin-induced apoptosis and renal dysfunction in TauT transgenic mice. Although cisplatin activated p53 and PUMA (a p53-responsive proapoptotic Bcl-2 family protein) in the kidneys of both wildtype and TauT transgenic mice, only wildtype animals demonstrated acute kidney injury. These data suggest that functional TauT plays a critical role in protecting against cisplatin-induced nephrotoxicity, possibly by attenuating a p53-dependent pathway.

Rickets in lion cubs at the London Zoo in 1889: some new insights

In 1889, when Dr John Bland-Sutton, a prominent surgeon in London, England, was consulted concerning fatal rickets in more than 20 successive litters of lion cubs at the London Zoo, he evaluated the role of diet relative to the development of rickets. He prescribed goat meat and bones and cod-liver oil to be added to the lean horse-meat diet of the cubs and their mothers. Rickets reversed, the cubs survived, and litters were reared successfully. In classic controlled studies conducted in puppies and young rats 3 decades later, the crucial role of calcium, phosphate, and vitamin D in both prevention and therapy of rickets was elucidated. Later studies led to the identification of the structural features of vitamin D. Although the Bland-Sutton interventional diet obviously provides calcium and phosphate from bones and vitamin D from cod-liver oil, other benefits of this diet were not initially recognized. Chewing bones promotes tooth and gum health and removes bacteria-laden tartar. Cod-liver oil also contains vitamin A, which is essential for the prevention of infection and for epithelial cell health. Taurine-conjugated bile salts are also necessary for the intestinal absorption of fat-soluble vitamins, including A and D. Moreover, unlike dogs and rats, all feline species are unable to synthesize taurine yet can only conjugate bile acids with taurine. This sulfur-containing beta-amino acid must be provided in the carnivorous diet of a large cat. Taurine-conjugated bile salts were provided in the oil cold-pressed from cod liver. The now famous Bland-Sutton "experiment of nature," namely, fatal rickets in lion cubs, was cured by the addition of minerals and vitamin D. However, gum health and the presence of taurine-conjugated bile salts undoubtedly permitted absorption of vitamin A and D, the latter promoting the cure of rickets.

Does taurine deficiency cause metabolic bone disease and rickets in polar bear cubs raised in captivity?

Rickets and fractures have been reported in captive polar bears. Taurine (TAU) is key for the conjugation of ursodeoxycholic acid (UDCA), a bile acid unique to bears. Since TAU-conjugated UDCA optimizes fat and fat-soluble vitamin absorption, we asked if TAU deficiency could cause vitamin D malabsorption and lead to metabolic bone disease in captive polar bears. We measured TAU levels in plasma (P) and whole blood (WB) from captive and free-ranging cubs and adults, and vitamin D3 and TAU concentrations in milk samples from lactating sows. Plasma and WB TAU levels were significantly higher in cubs vs captive and free-ranging adult bears. Vitamin D in polar bear milk was 649.2 +/- 569.2 IU/L, similar to that found in formula. The amount of TAU in polar bear milk is 3166.4 +/- 771 nmol/ml, 26-fold higher than in formula. Levels of vitamin D in bear milk and formula as well as in plasma do not indicate classical nutritional vitamin D deficiency. Higher dietary intake of TAU by free-ranging cubs may influence bile acid conjugation and improve vitamin D absorption.

Randomized Intervention for Children With Vesicoureteral Reflux (RIVUR): background commentary of RIVUR investigators

Because of the frequency of urinary tract infections in children, off-label use of antimicrobial prophylaxis is often the usual treatment of children with vesicoureteral reflux, and such use is increasingly being called into question; hence, a definitive study to determine the value of antimicrobial prophylaxis with regard to the recurrence of urinary tract infection and the incidence of renal scarring is essential. The currently recommended follow-up procedures (repeated urine cultures, renal and genitourinary imaging, antimicrobial therapy and prophylaxis, as well as other factors including cleanliness, adequate bladder and bowel emptying, and compliance with protocols) are expensive (in terms of time, attention to detail, and cost) and cumbersome. Such recommendations should be evidence-based.

Rationale and design issues of the Randomized Intervention for Children With Vesicoureteral Reflux (RIVUR) study

OBJECTIVE

Our goal is to determine if antimicrobial prophylaxis with trimethoprim/sulfamethoxazole prevents recurrent urinary tract infections and renal scarring in children who are found to have vesicoureteral reflux after a first or second urinary tract infection.

DESIGN, PARTICIPANTS, AND METHODS

The Randomized Intervention for Children With Vesicoureteral Reflux (RIVUR) study is a double-blind, randomized, placebo-controlled trial. Six hundred children aged 2 to 72 months will be recruited from both primary and subspecialty care settings at clinical trial centers throughout North America. Children who are found to have grades I to IV vesicoureteral reflux after the index febrile or symptomatic urinary tract infection will be randomly assigned to receive daily doses of either trimethoprim/sulfamethoxazole or placebo for 2 years. Scheduled follow-up contacts include in-person study visits every 6 months and telephone interviews every 2 months. Biospecimens (urine and blood) and genetic specimens (blood) will be collected for future studies of the genetic and biochemical determinants of vesicoureteral reflux, recurrent urinary tract infection, renal insufficiency, and renal scarring.

RESULTS

The primary outcome is recurrence of urinary tract infection. Secondary outcomes include time to recurrent urinary tract infection, renal scarring (assessed by dimercaptosuccinic acid scan), treatment failure, renal function, resource utilization, and development of antimicrobial resistance in stool flora.

CONCLUSIONS

The RIVUR study will provide useful information to clinicians about the risks and benefits of prophylactic antibiotics for children who are diagnosed with vesicoureteral reflux after a first or second urinary tract infection. The data and specimens collected over the course of the study will allow researchers to better understand the pathophysiology of recurrent urinary tract infection and its sequelae.

The taurine transporter: mechanisms of regulation

Taurine transport undergoes an adaptive response to changes in taurine availability. Unlike most amino acids, taurine is not metabolized or incorporated into protein but remains free in the intracellular water. Most amino acids are reabsorbed at rates of 98-99%, but reabsorption of taurine may range from 40% to 99.5%. Factors that influence taurine accumulation include ionic environment, electrochemical charge, and post-translational and transcriptional factors. Among these are protein kinase C (PKC) activation and transactivation or repression by proto-oncogenes such as WT1, c-Jun, c-Myb and p53. Renal adaptive regulation of the taurine transporter (TauT) was studied in vivo and in vitro. Site-directed mutagenesis and the oocyte expression system were used to study post-translational regulation of the TauT by PKC. Reporter genes and Northern and Western blots were used to study transcriptional regulation of the taurine transporter gene (TauT). We demonstrated that (i) the body pool of taurine is controlled through renal adaptive regulation of TauT in response to taurine availability; (ii) ionic environment, electrochemical charge, pH, and developmental ontogeny influence renal taurine accumulation; (iii) the fourth segment of TauT is involved in the gating of taurine across the cell membrane, which is controlled by PKC phosphorylation of serine 322 at the post-translational level; (iv) expression of TauT is repressed by the p53 tumour suppressor gene and is transactivated by proto-oncogenes such as WT1, c-Jun, and c-Myb; and (v) over-expression of TauT protects renal cells from cisplatin-induced nephrotoxicity.

Regulation of TauT by cisplatin in LLC-PK1 renal cells

Cisplatin is a commonly used chemotherapeutic agent that has a major limitation because of its nephrotoxicity. Since cisplatin-induced renal injury is mainly confined to the S3 segment of renal proximal tubules-the primary site for renal adaptive regulation of TauT-we hypothesize that TauT functions as an anti-apoptotic gene and plays a role in protecting renal cells from drug-induced nephrotoxicity. In the present study we demonstrated that expression of TauT was significantly reduced by cisplatin (50 muM) in LLC-PK1 cells. Down-regulation of TauT by cisplatin occurs at the transcriptional level in a dose-dependent manner, as demonstrated through a reporter gene driven by the TauT promoter. It appears that cisplatin down-regulates TauT expression, at least in part, through the p53-dependent pathway, since cisplatin induces the p53 expression, which, in turn, represses TauT. Cisplatin induces apoptosis of LLC-PK1 cells in a dose-dependent manner. However, forced over-expression of TauT by stable transfection of a taurine transporter cDNA (pNCT) in LLC-PK1 cells was able to attenuate cisplatin-induced down-regulation of taurine uptake by LLC-PK1 cells and protect renal tubular cells from apoptosis. The mechanism by which TauT serves as an anti-apoptotic gene in cisplatin-induced renal injury remains to be determined, but could relate to taurine-dependent cell volume regulation.

The future of pediatric nephrology

The delineation of renal disease in children dates to the 1880s with descriptions of Henoch's purpura, bladder exstrophy, renal rickets and nephritis. The discipline of pediatric nephrology mainly emerged during the 20th century in response to problems in fluid and electrolyte balance, characterization of the nephrotic syndrome, use of renal biopsy, antibiotic therapy of urinary tract infections, dialysis and transplantation in children, growth problems associated with chronic renal failure, detection and therapy of hypertension, and the creation of both national and international pediatric nephrology societies and a journal now in its 18th year. The development of molecular and cell biology, genetic and genomic techniques and bioinformatics methods underlie many future directions. We should anticipate further elucidation of single gene disorders, of complex trait analysis of disorders, such as diabetic nephropathy and hypertension, the interplay of developmental genes and gene products and interactions within the podocyte. Specific therapies directed against inflammation, vascular damage, cyst development, the ravages of proteinuria and graft rejection (or induction leading to tolerance) will be developed. Stem cell therapies may replace lost renal mass, even of specific nephron sites. Novel therapies will also modulate the cell cycle, tyrosine kinase signaling and apoptosis. In addition, drugs will be specifically tested in children for many renal conditions. Larger and more specialized registries will be developed; epidemiologic studies and exploration of large data sets will lead to clinical guidelines that are evidenced-based. There is a need for more careful measurement of glomerular filtration rate (GFR), proteinuria and cytokines, and a fuller appreciation of the nutritional and hormonal role of the kidney. Finally, the antecedents of adult renal disease and the need to intervene in a proactive fashion will be realized. Despite these impressive advances in care, the greatest challenges will be in providing children with renal disease access to well-trained pediatric nephrologists, especially in Asia (1 billion children), Africa, Central and South America, and in immigrant and refugee populations. Included in this challenge is the capacity to have affordable access to use of contemporary techniques, and effective medications and prevention strategies. The International Pediatric Nephrology Association (IPNA), its journal, and pediatric advocates will need to use their energies to take on these challenges.