Reflux nephropathy

Copy Number Variant Analysis and Genome-wide Association Study Identify Loci with Large Effect for Vesicoureteral Reflux

BACKGROUND

Vesicoureteral reflux (VUR) is a common, familial genitourinary disorder, and a major cause of pediatric urinary tract infection (UTI) and kidney failure. The genetic basis of VUR is not well understood.

METHODS

A diagnostic analysis sought rare, pathogenic copy number variant (CNV) disorders among 1737 patients with VUR. A GWAS was performed in 1395 patients and 5366 controls, of European ancestry.

RESULTS

Altogether, 3% of VUR patients harbored an undiagnosed rare CNV disorder, such as the 1q21.1, 16p11.2, 22q11.21, and triple X syndromes ((OR, 3.12; 95% CI, 2.10 to 4.54; P=6.35×10^-8) The GWAS identified three study-wide significant and five suggestive loci with large effects (ORs, 1.41-6.9), containing canonical developmental genes expressed in the developing urinary tract (WDPCP, OTX1, BMP5, VANGL1, and WNT5A). In particular, 3.3% of VUR patients were homozygous for an intronic variant in WDPCP (rs13013890; OR, 3.65; 95% CI, 2.39 to 5.56; P=1.86×10^-9). This locus was associated with multiple genitourinary phenotypes in the UK Biobank and eMERGE studies. Analysis of Wnt5a mutant mice confirmed the role of Wnt5a signaling in bladder and ureteric morphogenesis.

CONCLUSIONS

These data demonstrate the genetic heterogeneity of VUR. Altogether, 6% of patients with VUR harbored a rare CNV or a common variant genotype conferring an OR >3. Identification of these genetic risk factors has multiple implications for clinical care and for analysis of outcomes in VUR.

Renal scarring on DMSA scan is associated with hypertension and decreased estimated glomerular filtration rate in spina bifida patients in the age of transition to adulthood

OBJECTIVE

Improved management for spina bifida (SB) has increased the number of patients transitioning to adult care. This trend increases the importance of maintaining renal function concurrently with bladder function in patients with SB. Dimercaptosuccinic acid (DMSA) renal scanning is an optimal tool for investigating renal insufficiency in children with SB; however, the benefits of DMSA scans in adulthood are unclear. The role of DMSA renal scans for patients with SB during the transition to adulthood (15-25 years of age) to reveal their association with current renal function was investigated.

MATERIALS AND METHODS

DMSA renal scanning was routinely performed patients with SB aged 15-25 years concurrently with examination of serum creatinine, serum cystatin C, urinalysis, and blood pressure between January 2006 and August 2016. Hypertension was defined as systolic or diastolic pressure above the age-specific normal range. The estimated glomerular filtration rate (eGFR) using serum creatinine or cystatin C was calculated; decreased eGFR was defined as eGFR below 90 mL/min/1.73 m². Patients were divided into two groups according to the absence or presence of renal scarring on DMSA scan. Factors associated with renal function, including hypertension, decreased eGFR, and proteinuria, were compared between groups.

RESULTS

Eighty-seven patients (36 males and 51 females) were analyzed. Median age was 19 years (range 15-24 years); 28 patients (32%) had renal scarring. Patients with renal scarring had significantly higher rates of hypertension (n = 13, 46%) and decreased eGFR (n = 5, 18%). However, there was no difference in proteinuria between the groups (Table). The group with renal scarring had significantly lower eGFR.

DISCUSSION

This study showed that DMSA scans in patients with SB aged between 15 and 25 years were useful for assessing renal scarring despite a history of febrile urinary tract infection. DMSA scans could be performed in all patients with SB in the transition to adulthood to detect renal scarring. This study also showed that renal scarring was associated with hypertension and decreased eGFR in this age group. Treatment with antihypertensive drugs should be considered for patients with SB with renal scarring in this age range to protect renal function.

CONCLUSION

Spina bifida patients in the age of transition to adulthood with renal scarring already showed signs of chronic kidney disease, suggesting that DMSA renal scans could be useful to identify patients who require close monitoring of renal function.

Reflux nephropathy and the risk of preeclampsia and of other adverse pregnancy-related outcomes: a systematic review and meta-analysis of case series and reports in the new millennium

BACKGROUND

Reflux nephropathy is a common urinary tract malformation, and a substantial cause of morbidity in women of childbearing age. While recent studies provide further new information on pregnancy-related outcomes, their results are heterogeneous and a systematic meta-analysis may help the interpretation. The aim of this review was to analyze pregnancy-related outcomes in the recent literature on reflux nephropathy (2000-2016), to perfect the estimation of risks, and to identify specific research needs.

METHODS

We searched Medline, EMBASE and the Cochrane review databases for the period 2000-2016 (PROSPERO registration no. 42016042713).

SELECTION CRITERIA

all case series and case reports dealing with reflux nephropathy and reporting on at least one pregnancy outcome. Data were extracted from eligible case series (≥ 6 cases). For the outcomes preeclampsia (PE), pregnancy-induced hypertension (PIH), preterm birth, and newborns small for gestational age, we employed as a control group the low-risk pregnancies from a multicenter database including 1418 live-born singletons. Case reports were analyzed narratively.

RESULTS

The search retrieved 2507 papers, of which 7 case series and 4 case reports were retained. The series report on 434 women with 879 pregnancies; no study reported controls. Compared to the low-risk controls, the meta-analysis showed an increased risk of PIH (odds ratio, OR 5.55; confidence interval, CI 3.56-8.66), PE (OR 6.04; CI 2.41-15.13), and all hypertensive disorders combined (OR 10.43; CI 6.90-15.75). No difference was observed in preterm delivery and caesarean sections. A higher incidence of stillbirth was reported in one paper. Conversely, the 4 case reports (on 10 pregnancies) alert us to a potentially severe complication, hydro(uretero)nephrosis with or without infection.

CONCLUSION

Reflux nephropathy is associated with an increased risk of PIH and PE, but not of preterm delivery, suggesting the occurrence of late 'maternal' PE. The finding of a higher incidence of stillbirths in one series requires further analysis. Strict follow-up of these women is needed, in particular in late pregnancy stages, to avoid and manage in particular hypertensive pregnancy complications.

Kidney atrophy vs hypertrophy in diabetes: which cells are involved?

One of the first structural changes in diabetic nephropathy (DN) is the renal enlargement. These changes resulted in renal hypertrophy in both glomerular and tubular cells. Shrink in the kidney size, which described as kidney atrophy resulted from the loss of nephrons or abnormal nephron function and lead to loss of the kidney function. On the other hand, increase in kidney size, which described as hypertrophy resulted from increase in proximal tubular epithelial and glomerular cells size. However overtime, tubular atrophy and tubulointerstitial fibrosis occurs as subsequent changes in tubular cell hypertrophy, which is associated with the infiltration of fibroblast cells into the tubulointerstitial space. The rate of deterioration of kidney function shows a strong correlation with the degree of tubulointerstitial fibrosis. A consequence of long-standing diabetes/hyperglycemia may lead to major changes in renal structure that occur but not specific only to nephropathy. Identifying type of cells that involves in renal atrophy and hypertrophy may help to find a therapeutic target to treat diabetic nephropathy. In summary, the early changes in diabetic kidney are mainly includes the increase in tubular basement membrane thickening which lead to renal hypertrophy. On the other hand, only renal tubule is subjected to apoptosis, which is one of the characteristic morphologic changes in diabetic kidney to form tubular atrophy at the late stage of diabetes.

Vesicoureteral reflux and the extracellular matrix connection

Primary vesicoureteral reflux (VUR) is a common pediatric condition due to a developmental defect in the ureterovesical junction. The prevalence of VUR among individuals with connective tissue disorders, as well as the importance of the ureter and bladder wall musculature for the anti-reflux mechanism, suggest that defects in the extracellular matrix (ECM) within the ureterovesical junction may result in VUR. This review will discuss the function of the smooth muscle and its supporting ECM microenvironment with respect to VUR, and explore the association of VUR with mutations in ECM-related genes.

Voiding cystourethrogram: How much should we be selective?

OBJECTIVE

In this study, we examined the patients' characteristics, who underwent voiding cystourethrography (VCUG), in order to determine any selectivity for indication of this invasive method.

MATERIAL AND METHODS

After exclusion of indications of neurogenic bladder or antenatal hydronephrosis and control VCUGs, 159 VCUGs performed in our clinic within one year were evaluated. Patients are divided into three groups accoding to age. Clinical characteristic and findings of renal ultrasonography (US) and renal scintigraphy were examined.

RESULTS

Vesicoureteral reflux (VUR) was detected in 61 (38.3%) of 159 patients who underwent cystourethrographic examinations, in 45.8% of the patients with a history of recurrent urinary tract infection (UTI), in 22.0% of the patients with pathological urinary system US without history of recurrent UTI. High-grade reflux rate was significantly more frequent in renal units with pathological US findings. Severe scar was significantly more frequent in renal units with high-grade reflux when compared to renal units without reflux and those with low-grade reflux. Predictive values of recurrent UTI, scarring status and pathological US for VUR were separately analyzed and seen that likelihood of indicating VUR was increased when all 3 risk factors were assessed together.

CONCLUSION

Vesicoureteral reflux is a problem in which diagnostic process and management strategy should have to be considered in individualized manner for each patient. Before prescribing invasive VCUG, imaging urinary system by US and scintigraphy and determining whether there is recurrent UTI will improve selectivity and success of VCUG.

[Vesico-ureteral reflux: Diagnosis and treatment recommendations]

BACKGROUND

Vesico-ureteral reflux (VUR) is one of the most common urologic diseases in childhood. About every third child that presents with a urinary tract infection (UTI) has urinary reflux to the ureter or kidney. Demonstration of a backflow of urine into the ureters or kidneys proves vesicoureteral reflux. In unclear cases, a positioned instillation of contrast agent (PIC) cystogram might be performed and is able to prove vesico-ureteral reflux.

OBJECTIVES

Since low-grade VUR has a high probability of maturation and self-limitation, infants with VUR should be given prophylactic antibiotics during their first year of life, reevaluating the status of VUR after 12 months. The aim of any treatment is to prevent renal damage.

THERAPY

The individual risk of renal scarring is decisive for the choice of adequate therapy. This risk is mainly dependent on reflux grade, age, and gender of the child as well as parental therapy adherence. In principle, therapeutic options include conservative as well as endoscopic or open surgical antireflux therapies.

CONCLUSION

Decisions on treatment should be made individually with parents taking into account all the findings available.

Clinical characteristics and prevalence of complications of chronic kidney disease in children: the Taiwan Pediatric Renal Collaborative study

BACKGROUND

Little information is available regarding the clinical characteristics and prevalence of complications in children with chronic kidney disease (CKD), especially in early disease stages. The objective of this study was to determine the clinical characteristics and prevalence of complications in children with predialytic CKD.

METHODS

This multicenter, cross-sectional study enrolled children at all stages of predialytic CKD. Children who were between the ages of 1 year and 18 years and who fulfilled the clinical criteria of CKD were included in the study. Baseline demographic data, previous history, clinical characteristics, and laboratory data were collected.

RESULTS

A total of 757 children were included in the study. The median age at the time of enrollment was 10.6 years; 397 patients (52.4 %) were males. A total of 39.0 % of the patients were in CKD stage 1, 37.6 % were in stage 2, 14.8 % were in stage 3, 3.0 % were in stage 4, and 5.5 % were in stage 5. Nonglomerular renal diseases were the primary cause of CKD, comprising 51.9 % of the patients with CKD. The age at disease onset, gender, CKD stage distribution, and proportion of co-morbidities varied between the glomerular and nonglomerular CKD cases. Anemia, hyperlipidemia, hypocalcemia, and hyperphosphatemia were more prevalent in patients with glomerular CKD. The overall prevalence of complications was as follows: uncontrolled blood pressure, 44.1 %; anemia, 34.2 %; hyperlipidemia, 44.9 %; short stature, 10.3 %; and failure to thrive, 8.2 %. Uncontrolled blood pressure (BP), anemia, and hyperlipidemia were common, even in the early CKD stages. The prevalence of CKD complications generally increased with the worsening stage of CKD.

CONCLUSIONS

This study reveals differences in CKD etiology and prevalence of specific complications according to the stage of CKD. Early recognition and awareness of complications are mandatory for clinicians during the follow-up visits of children with CKD.

Hypertension and symptomatic hypokalemia in a patient with simultaneous unilateral stenoses of intrarenal arteries and mesangioproliferative glomerulonephritis

We present the case of a young patient with hypertension and unprovoked symptomatic hypokalemia. His workup uncovered secondary aldosteronism, moderate proteinuria, and, quite unusually, concurrent chronic hepatitis B. Detailed investigations, including renal angiography, renal vein sampling, and kidney biopsy, showed unilateral renin hypersecretion due to intrarenal arterial stenoses and mesangioproliferative glomerulonephritis, presumed to be secondary to hepatitis B infection. Targeted pharmacotherapy reversed all clinical manifestations, normalizing blood pressure and serum potassium level and achieving full remission of proteinuria and loss of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg), and a dramatic decrease in viral load.

Vesicoureteral reflux and reflux nephropathy

Primary vesicoureteral reflux (VUR) is the commonest congenital urological abnormality in children, which has been associated with an increased risk of urinary tract infection (UTI) and renal scarring, also called reflux nephropathy (RN). In children, RN is diagnosed mostly after UTI (acquired RN) or during follow-up for antenatally diagnosed hydronephrosis with no prior UTI (congenital RN). The acquired RN is more common in female children, whereas the congenital RN is more common in male children. This observation in children might help explain the differences in the clinical presentation of RN in adults, with males presenting mostly with hypertension, proteinuria, and progressive renal failure as compared with females who present mostly with recurrent UTI and have a better outcome. Known risk factors for RN include the severity of VUR, recurrent UTI, and bladder-bowel dysfunction; younger age and delay in treatment of UTI are believed to be other risk factors. Management of VUR is controversial and includes antimicrobial prophylaxis, surgical intervention, or surveillance only. No evidence-based guidelines exist for appropriate follow-up of patients with RN.

Could prophylactic antibiotics be stopped in patients with history of vesicoureteral reflux?

OBJECTIVE

To compare the incidence and type of urinary tract infection (UTI) in patients with primary vesicoureteral reflux (VUR) diagnosed after a febrile UTI while they were on prophylactic antibiotics (PA) and after stopping PA.

MATERIALS AND METHODS

Criteria to discontinue PA were: no UTI during 12+ or more months on PA, old enough to communicate UTI symptoms, potty trained and absence of risk factors for UTI. Patients with at least 1 year of follow up without PA were included (n=77). We recorded: age at which PA was indicated and stopped, time on and off PA, incidence and type of UTI (cystitis vs acute pyelonephritis (APN)), and renal scan results.

RESULTS

PA was started and stopped at a mean age of 18.5 and 61 months, respectively. Mean time on PA was 39 months (range 12-95): 25 patients had 44 UTI episodes (0.17 episodes/patient/year), and 31 (70%) of them were APN. Mean time of antibiotics was 44.5 months (range 12-162): 13 patients had 24 UTI episodes (0.08 episodes/patient/year), eight (33%) of which were APN (P<0.05). A renal scan was performed in 71 patients after the index infection and repeated in 12. Two patients lost renal function while still on PA.

CONCLUSION

Discontinuing PA in patients with history of VUR is a safe practice and should be considered as a management option.

Cell biology and physiology of the uroepithelium

The uroepithelium sits at the interface between the urinary space and underlying tissues, where it forms a high-resistance barrier to ion, solute, and water flux, as well as pathogens. However, the uroepithelium is not simply a passive barrier; it can modulate the composition of the urine, and it functions as an integral part of a sensory web in which it receives, amplifies, and transmits information about its external milieu to the underlying nervous and muscular systems. This review examines our understanding of uroepithelial regeneration and how specializations of the outermost umbrella cell layer, including tight junctions, surface uroplakins, and dynamic apical membrane exocytosis/endocytosis, contribute to barrier function and how they are co-opted by uropathogenic bacteria to infect the uroepithelium. Furthermore, we discuss the presence and possible functions of aquaporins, urea transporters, and multiple ion channels in the uroepithelium. Finally, we describe potential mechanisms by which the uroepithelium can transmit information about the urinary space to the other tissues in the bladder proper.

Tubulointerstitial nephritis associated with IgG4-related autoimmune disease

Autoimmune pancreatitis is a chronic fibroinflammatory condition primarily affecting the pancreas. Recent accumulating evidence suggested that autoimmune pancreatitis is a systemic autoimmune disease (immunoglobulin G4 [IgG4]-related autoimmune disease) affecting various organs with dense infiltration of IgG4-positive mononuclear cells. Tubulointerstitial nephritis is still a mysterious disease with an unknown cause. We report 2 cases of tubulointerstitial nephritis associated with autoimmune pancreatitis. In these patients, dense infiltrations of IgG4-positive mononuclear cells were observed in renal interstitium, with high serum IgG4 levels. Furthermore, in patient 1, who had sclerosing cholangitis, serum alkaline phosphatase and serum creatinine levels changed synchronously. Steroid therapy was followed by improved renal function and serum IgG4 levels in both patients. Because tubulointerstitial nephritis associated with IgG4-related autoimmune disease shows a favorable response to steroids and the renal dysfunction and pancreatic dysfunction are reversible, awareness of this entity is necessary for early diagnosis and prompt treatment. In addition, these cases support the hypothesis that IgG4-related autoimmune disease could be one cause of tubulointerstitial nephritis.

Disruption of ROBO2 is associated with urinary tract anomalies and confers risk of vesicoureteral reflux

Congenital anomalies of the kidney and urinary tract (CAKUT) include vesicoureteral reflux (VUR). VUR is a complex, genetically heterogeneous developmental disorder characterized by the retrograde flow of urine from the bladder into the ureter and is associated with reflux nephropathy, the cause of 15% of end-stage renal disease in children and young adults. We investigated a man with a de novo translocation, 46,X,t(Y;3)(p11;p12)dn, who exhibits multiple congenital abnormalities, including severe bilateral VUR with ureterovesical junction defects. This translocation disrupts ROBO2, which encodes a transmembrane receptor for SLIT ligand, and produces dominant-negative ROBO2 proteins that abrogate SLIT-ROBO signaling in vitro. In addition, we identified two novel ROBO2 intracellular missense variants that segregate with CAKUT and VUR in two unrelated families. Adult heterozygous and mosaic mutant mice with reduced Robo2 gene dosage also exhibit striking CAKUT-VUR phenotypes. Collectively, these results implicate the SLIT-ROBO signaling pathway in the pathogenesis of a subset of human VUR.

Vesicoureteric reflux and tumor necrosis factor-alpha gene polymorphism

AIM

To determine the role of tumor necrosis factor-alpha (TNF-alpha) gene polymorphism in promoting renal scarring among patients with vesicoureteric reflux (VUR). This genetic variant involves a guanosine to adenine transition at position -308, and this single-base polymorphism is associated with increased transcription of the TNF-alpha gene. Recent studies suggest that the TNF-alpha gene may be associated with predisposition to renal scarring.

PATIENTS AND METHODS

A total of 195 (51.8% females) patients with VUR demonstrated by voiding cystourethrogram were recruited, 126 of them with reflux nephropathy diagnosed by dimercaptosuccinic scan. The control group included 266 healthy individuals. Genotyping was performed by polymerase chain reaction and digestion with a restriction enzyme.

RESULTS

Allele frequencies of -308G and -308A were 83.8% and 16.2%, respectively in patients with VUR and 88.9% and 11.1%, respectively in controls (P<0.05). No differences were found in genotype distribution related to presence/absence of renal scars. There was no relationship between TNF-alpha genotype and grade of VUR or the presence of proteinuria.

CONCLUSIONS

Our data suggest that the TNF-alpha AA genotype is not associated with reflux nephropathy. The TNF-alpha-308A allele could be related to a higher susceptibility to VUR.

Predictive factors of chronic kidney disease in severe vesicoureteral reflux

The aim of this retrospective cohort study was to evaluate independent predictive factors of chronic kidney disease (CKD) in children with severe bilateral primary vesicoureteral reflux (VUR). Between 1970 and 2004, 184 patients were diagnosed with VUR (grades III-V) and were systematically followed up at a single tertiary renal unit. CKD was defined as estimated glomerular filtration rate <75 ml/min per 1.73 m2 body surface area in two consecutive examinations. Risk of CKD was analyzed by the Kaplan-Meier method and Cox's regression model. The probability of CKD for patients with bilateral severe reflux was estimated at 15% by 10 years after VUR diagnosis. After adjustment, four variables remained independently associated with CKD during follow-up: age at diagnosis >24 months [relative risk (RR)=4.8, 95% confidence interval (95%CI), 1.8-12.7, P<0.001], VUR grade V (RR=3.5, 95%CI, 1.5-7.9, P=0.002), bilateral renal damage (RR=2.86, 95%CI, 1.3-6.1, P=0.007), and decade of admission after 1990 as a protective factor (RR=0.16, 95%CI 0.06-0.43, P<0.001). A delay in the diagnosis of VUR more than 12 months after urinary tract infection (UTI) was also a predictive factor in an alternative model (RR=2.2, 95%CI, 1.1-6.6, P=0.03). Prognosis regarding renal function was relatively poor after a long-term follow-up of patients with bilateral severe reflux.

Urinothorax associated with VURD syndrome

VURD syndrome is a congenital genitourinary anomaly combining posterior urethral V alves, U nilateral vesicoureteral R eflux and renal D ysplasia. We report on a case of VURD syndrome presenting with acute renal failure and respiratory distress syndrome due to urinothorax. Urinothorax is a rarely reported complication of obstructive uropathy, but has not been linked to VURD syndrome. The diagnosis of urinothorax was confirmed by demonstration of a pleural fluid to serum creatinine ratio greater than one. Without tube thoracotomy drainage, urinothorax resolved rapidly after urinary catheterization and the renal recovery was also excellent after primary valve ablation. We discuss the diagnosis and management of urinothorax and the possible protective effect of urinoma, urinothorax, and unilateral vesicoureteral reflux on the renal function. We consider that urinothorax and urinoma may be deemed to be the extension of the clinical spectrum of VRUD syndrome. Excellent renal prognosis in our case also favors the protective effect provided by the buffer of pressure from unilateral vesicoureteral reflux, urinoma and urinothorax.

The uroepithelium: not just a passive barrier

The uroepithelium lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, where it forms a tight barrier that allows for retention of urine, while preventing the unregulated movement of ions, solutes, and toxic metabolites across the epithelial barrier. In the case of the bladder, the permeability barrier must be maintained even as the organ undergoes cyclical changes in pressure as it fills and empties. Beyond furthering our understanding of barrier function, new analysis of the uroepithelium is providing information about how detergent-insoluble membrane/protein domains called plaques are formed at the apical plasma membrane of the surface umbrella cells, how mechanical stimuli such as pressure alter exocytic and endocytic traffic in epithelial cells such as umbrella cells, and how changes in pressure are communicated to the underlying nervous system.

Prevalence of vesicoureteral reflux in neonatal urinary tract infection

Vesicoureteral reflux (VUR) after a first episode of urinary tract infection (UTI) is apparently diagnosed much more frequently (25%-40%) in children than in neonates. The aims of the study were to determine the actual rate of VUR in neonates with UTI and to define the clinical clues to its diagnosis. The study sample included term infants with a diagnosis of UTI during their first month of life who were seen in this hospital between January 1997 and May 1999. All infants underwent complete diagnostic work-up (renal ultrasound and voiding cystourethrography [VCUG]). The medical files were reviewed for patient sex, age at UTI diagnosis, laboratory findings (including causative pathogen), and ultrasonographic findings. These parameters were correlated with the finding of VUR on VCUG. Sixty-four neonates (55 males, 9 females) with UTI were included in this study. UTI was 6 times more common in males than females, although the incidence of VUR was equal between the sexes (about 20%). The presence of VUR was associated with a significantly younger age at presentation of UTI (11.4+/-4 vs 16.9+/-6.6 days, p<0.01). VUR was diagnosed at a fourfold higher rate in neonates with Klebsiella-induced UTI compared to those with E. Coli-UTI. In 80% of those with significantly abnormal ultrasonographic findings VUR was found on VCUG. Jaundice was noted at UTI diagnosis 3 times more often in infants with VUR, and elevated creatinine level, 2.5 times more often.

Primary ureteral reflux: emerging insights from molecular and genetic studies

The incidence of primary vesicoureteral reflux is about 1% to 2% of the general population and is as high as 50% in siblings as well as offspring of affected patients, suggesting autosomal dominant inheritance. The current diagnosis of vesicoureteral reflux involves voiding cystourethrograms, which are invasive and costly. Consequently, vesicoureteral reflux screening in siblings and offspring is not routinely practiced, because of the known high risk. Early detection of vesicoureteral reflux will be valuable for prevention of reflux nephropathy, because the incidence of reflux nephropathy can be reduced effectively by antibiotic prophylaxis. Furthermore, the presence of reflux nephropathy can only be accurately assessed currently by dimercapto-succinic acid nuclear scans, which are costly, time and labor intensive, and often require conscious sedation by a pediatric anesthesiology team. As a result, the clinical assessment of reflux nephropathy is also not routinely practiced. There is a pressing need to develop less invasive and less costly tests for the early diagnosis of primary vesicoureteric reflux and reflux nephropathy. Recent molecular and genetic studies have greatly increased our understanding of vesicoureteral reflux and provide a promise of novel non-invasive tests. Targeted disruption of angiotensin type II receptor and uroplakin III genes result in the phenotype of primary vesicoureteral reflux. There are characteristic patterns of message and protein changes in the knockout animals, providing the basis for detection of genetic mutations leading to vesicoureteral reflux in humans by studying differential gene expression by functional genomics methodology. The urothelium is also known to secrete proteins into the urine. Preliminary studies showed unique fingerprints in urinary protein patterns in children with primary VUR, providing the basis for developing novel noninvasive molecular diagnostic tests of vesicoureteral reflux by proteomics methodology.

Vesicoureteric reflux and reflux nephropathy as seen at a tertiary care adult nephrology service in India--an analysis of 86 patients

Clinical features and risk factors for renal failure in patients with reflux nephropathy (RN) as seen in an adult nephrology service are likely to be different than those seen in a pediatric service. There are only a few studies on adults with vesicoureteric reflux (VUR) and RN and data on RN as seen in developing countries is still evolving. Retrospective analysis of records of patients diagnosed to have VUR by conventional micturating cystourethrogram over a 13 year period, as seen in the adult nephrology services of this tertiary care hospital in north India was carried out. Results are presented as mean +/- 2 SD. Unpaired t-test was used to compare means, chi-square test to define associations, and logistic regression analysis was done to define risk factors. Out of 86 patients diagnosed to have VUR, 69 (80.2%) were males and 22 (25.6%) were children. The mean age at presentation was 24.3 +/- 14.5 years and at onset of symptoms was 19.64 +/- 14.8 years. Sixty-nine (80.2%) patients had chronic renal failure (CRF) at presentation, including 33 (38.4%) patients who already had end stage renal failure (ESRF) at presentation in whom reflux was diagnosed during routine pretransplant evaluation and these constituted 5.5% of all ESRF patients. The clinical features at presentation were hypertension in 51 (59.3%), recurrent urinary tract infection (UTI) in 31 (36.1%), history of stones in 7 (8.1%), and gross hematuria in 4 (4.7%). Patients with history of recurrent UTI were more likely to be females (p < 0.01) and to present without renal failure (p < 0.05). Proteinuria > 1 g/day was significantly associated (p < 0.02) with hypertension at presentation. Patients who presented with renal failure were more likely to be males (p < 0.05), not to have history of recurrent UTI (p < 0.05), have proteinuria > 1 g/day (p < 0.02) and higher grades (grades IV and V) of reflux (p < 0.05). On logistic regression analysis, higher age of onset (odds ratio 4.6, p < 0.03), proteinuria > 1 g/day (odds ratio 3.8, p < 0.05), and male gender (odds ratio 3.5, p < 0.05) were significant risk factors for presentation for the first time with renal failure. The clinical features and course of VUR and RN as seen in India are different from those reported from elsewhere. The vast majority of patients in India are males and almost two thirds do not have a past history of UTI. Renal failure is present in more than three fourths of patients when a diagnosis of reflux is made and one third of all patients present with ESRD. Patients with a prior history of UTI are more commonly females and are less likely to have renal failure at presentation. Higher age of onset of symptoms, proteinuria > 1 g/day and male gender were risk factors for the development of renal failure. It is likely that these asymptomatic patients remain undetected during childhood, presenting late only after having incurred severe renal damage.

Reliability of contrast enhanced sonography with harmonic imaging for detecting early renal scarring in experimental pyelonephritis in a porcine model: preliminary results

PURPOSE

Contrast medium enhanced harmonic ultrasound is a recently developed ultrasound technique that improves the assessment of renal parenchymal vascularity. We performed a preliminary study to define the ability of contrast enhanced ultrasound with harmonic imaging to detect and localize renal scars in a porcine model of experimentally induced pyelonephritis.

MATERIALS AND METHODS

Vesicoureteral reflux was surgically induced in 10 pigs weighing 10 kg. with the contralateral kidney serving as a control. Approximately 4 weeks after the creation of vesicoureteral reflux cystography confirmed reflux. Infection was induced by placing a suspension of paraffin broth impregnated with Escherichia coli in the bladder of each pig. At 4 to 8 weeks (mean 6.5) after the induction of infection a radiologist blinded to the side of the previous procedure performed conventional gray scale ultrasound, color Doppler ultrasound and contrast enhanced ultrasound with harmonic power imaging. The animals were sacrificed; the kidneys were inspected and tissues from the upper, mid and lower poles were sent for culture and histological examination. Histology results were compared with the findings of the 3 ultrasound modalities.

RESULTS

All 10 pigs survived the surgical procedures with no complications. Post-contrast harmonic ultrasound images were available in 9 pigs (18 renal units). Harmonic ultrasound revealed decreased blood flow in 11 renal units, including the upper pole in 7, lower pole in 3, and upper and lower poles in 2. Renal tissue cultures were positive in 11 renal units (6 refluxing units). Histological findings revealed fibrosis in 10 renal units (8 refluxing units). Harmonic ultrasound findings in these 10 renal units showed 9 with changes consistent with inflammation or scars. Using histological results as the gold standard for renal injury harmonic ultrasound was more sensitive than gray scale ultrasound for detecting renal injury with 90% sensitivity, 75% specificity, 81% positive predictive value and 85% negative predictive value.

CONCLUSIONS

Preliminary results indicate that contrast enhanced ultrasound with harmonic imaging is a sensitive method for determining renal scarring without the need for radiation exposure. It may be prove to be a useful adjunct for evaluating children who present with urinary tract infection.

A noninvasive test for vesico-ureteric reflux in children

OBJECTIVE

To report the development and testing of a device for the noninvasive diagnosis of vesico-ureteric reflux (VUR) which avoids the need for urethral catheterization (currently required to reliably determine the presence of VUR), and which thus avoids the anxiety of parents and patients that causes many families to refuse such evaluation.

PATIENTS AND METHODS

Fifty-four children (49 girls and five boys, mean age 7.2 years, range 4-14) previously evaluated as having VUR volunteered to participate; no child was symptomatic at the time of the study. Refluxing units were known to be present by voiding cysto-urethrography (within 1 year, mean 7 months) in 45 and absent in 16. The device developed acquires electronically processed acoustic signals from the child during an observed urination. The signals are then analysed 'off-line' to determine the presence or absence of VUR. The initial preparation for the test included: (i) a full bladder [at least 0.80 x ((2 + age) x 30 mL)] measured by ultrasonography; and (ii) localization of the pelvi-ureteric junction by ultrasonography to accurately place the device's sensors on the child's back. The children were then positioned at a commode after placing the sensors; the recording was started and continued until voiding occurred. The children were tested with the recording and analysis team unaware of the presence and/or degree of VUR. The first 47 studies were single-kidney examinations and the remaining seven included simultaneous monitoring of both kidneys.

RESULTS

Sixty-one renal units were assessed and interpretable signals were obtained from 54 (89%). There were seven episodes of 'system failure' when no interpretable data were obtained. One unit with no VUR had a 'reflux' signal; in four kidneys, spontaneous (two) and postsurgical (two) resolution of reflux was predicted by the testing and subsequently verified by cyclic radionuclide cystography.

CONCLUSIONS

This noninvasive diagnostic technique detected VUR in 35 of 37 refluxing units and verified no reflux in 16 of 17 units without VUR. Further refinements may allow this technology to be used in all children with suspected VUR.

Ablation of uroplakin III gene results in small urothelial plaques, urothelial leakage, and vesicoureteral reflux

Urothelium synthesizes a group of integral membrane proteins called uroplakins, which form two-dimensional crystals (urothelial plaques) covering >90% of the apical urothelial surface. We show that the ablation of the mouse uroplakin III (UPIII) gene leads to overexpression, defective glycosylation, and abnormal targeting of uroplakin Ib, the presumed partner of UPIII. The UPIII-depleted urothelium features small plaques, becomes leaky, and has enlarged ureteral orifices resulting in the back flow of urine, hydronephrosis, and altered renal function indicators. Thus, UPIII is an integral subunit of the urothelial plaque and contributes to the permeability barrier function of the urothelium, and UPIII deficiency can lead to global anomalies in the urinary tract. The ablation of a single urothelial-specific gene can therefore cause primary vesicoureteral reflux (VUR), a hereditary disease affecting approximately 1% of pregnancies and representing a leading cause of renal failure in infants. The fact that VUR caused by UPIII deletion seems distinct from that caused by the deletion of angiotensin receptor II gene suggests the existence of VUR subtypes. Mutations in multiple gene, including some that are urothelial specific, may therefore cause different subtypes of primary reflux. Studies of VUR in animal models caused by well-defined genetic defects should lead to improved molecular classification, prenatal diagnosis, and therapy of this important hereditary problem.

Hypothyroidism mimicking chronic renal failure in reflux nephropathy

An adolescent with a history of pyelonephritis and renal scarring had antireflux surgery at the age of 2.5 years. His serum creatinine was high at the age of 14 years (133 micromol/l; glomerular filtration rate (GFR) 56 ml/min x 1.73 m(2)), and reflux nephropathy with chronic renal failure was diagnosed. Because of a fall in height velocity, endocrinological investigations were performed six months later which showed hypothyroidism caused by autoimmune thyroiditis. Substitution with thyroxine was started; renal function improved to normal six months later (GFR 108 ml/min x 1.73 m(2)). Metabolic changes of hypothyroidism led to a reduction of GFR in this patient and mimicked chronic renal failure.

Recent advances in the understanding and management of primary vesicoureteral reflux and reflux nephropathy

Vesicoureteral reflux and reflux nephropathy continue to be active areas of clinical investigation. There is conclusive evidence that vesicoureteral reflux is inherited. Prenatal diagnosis offers the opportunity for early recognition and intervention that may reduce the incidence of complications of vesicoureteral reflux such as pyelonephritis episodes and the development of reflux nephropathy.