Renal tubular markers as screening tools for severe vesicoureteral reflux

Update of the Spanish clinical practice guideline for urinary tract infection in infants and children. Summary of recommendations for diagnosis, treatment and follow-up

The management of urinary tract infection (UTI) in infants and children has changed significantly over the past few decades based on scientific evidence that questioned the efficacy of strategies used to prevent kidney injury and subsequent progression to chronic kidney disease, which is very unlikely in most paediatric cases. However, there is still substantial heterogeneity in its management and uncertainty regarding the diagnosis, indication of imaging tests, treatment or follow-up in these patients. The Spanish clinical practice guideline has been updated through the review of the literature published since 2009 and a rigorous evaluation of current clinical practice aspects, taking into account the evidence on the benefits of each intervention in addition to its risks and drawbacks to attempt to provide more precise recommendations.

Nanocrystal-induced chronic tubular-nephropathy in tropical countries: diagnosis, mitigation, and eradication

In tropical countries, a mysterious tubulo-interstitial chronic renal disease (CKD), unrelated to diabetes, hypertension, and immunological causes, manifested four decades ago. Approximately 25,000 primarily middle-aged male farmers succumb annually to this crystal-tubular nephropathy (CTN). Without any known causative factors, it was identified as CKD of unknown aetiology (CKDu). Because multiple factors contribute to causing it later, was changed to CKD of multi-factorial (CKDmfo). Despite no evidence, it was hypothesised to cause by agrochemicals or heavy metals in food or drinking contaminated water. However, current data suggest that the CKD-CTN is due to natural geogenic water contamination. Consumption of concentrated stagnant groundwater from deep-dug wells and tube wells containing hard water and fluoride, overdecades is necessary for its clinical manifestations. In all affected countries have prolonged annual dry seasons that led to the evopo-concentration of ions and minerals in groundwater, making hard water even more unpalatable, thus, peasants consume lesser amounts of water. They develop chronic dehydration from daily exposure to hot climatic conditions aggravated by regular alcohol intake. These conditions provide a highly conducive environment-a perfect storm for calcium phosphate (CaPO₄) crystal formation in renal tissues. Our recent histological and preliminary electron microscopic data reveal deposition of CaPO₄ crystals and nano-tubes in kidneys. While CaPO₄ nano-minerals are unstable, the presence of fluoride ions stabilises and allows their growth. This new concept paves the path for highly cost-effective, straightforward local solutions to protect farm workers and eliminate the disease, without embarking on expensive medications, interventions, or building hospitals. Chronic dehydration-associated CKD-CTN is preventable by increased consumption of potable water. Increasing clean water consumption reduces CKD-CTN incidence, and associated morbidities and premature deaths. However, the damage becomes irreversible when the disease advances beyond CKD stage IIIB. The incidence of this deadly renal failure can be prevented by its education, lifestyle changes, and increased water consumption, not by treating the renal disease or expanding dialysis centres/hospitals, or transplantation services. Eradication of CKD-CTN cost significantly less than the current approach of treating affected persons and unnecessarily expanding health infrastructure. Since the manifestation of CKD-CTN is due to consuming naturally contaminated drinking water (with calcium containing hard water and fluoride), it is not difficult to remove these to prevent CKD-CTN: thus, international assistance is unwarranted for its eradication. The straightforward approaches described here will prevent CKD-CTN and save thousands of lives in affected farming communities.

Kidney concentrating capacity in children with autosomal recessive polycystic kidney disease is linked to glomerular filtration and hypertension

BACKGROUND

Impaired kidney concentration capacity is present in half of the patients with autosomal dominant polycystic kidney disease (ADPKD). The kidney concentrating capacity was further impaired within the animal model of autosomal recessive polycystic kidney disease (ARPKD). To date, only one small study has investigated it in children having ARPKD. Therefore, we aimed to study the kidney concentrating ability in a larger cohort of children with ARPKD.

METHODS

Eighteen children (median age 8.5 years, range 1.3-16.8) were retrospectively investigated. A standardized kidney concentrating capacity test was performed after the application of a nasal drop of desmopressin (urine osmolality > 900 mOsmol/kg). The glomerular filtration rate was estimated using the Schwartz formula (eGFR) and blood pressure (BP) was measured as office BP.

RESULTS

Kidney concentrating capacity was decreased (urine osmolality < 900 mOsmol/kg) in 100% of children with ARPKD. The median urine osmolality after desmopressin application was 389 (range 235-601) mOsmol/kg. Sixteen patients (89%) were defined as hypertensive based on their actual BP level or their use of antihypertensive drugs. The maximum amounts of urinary concentration correlated significantly with eGFR (r = 0.72, p < 0.0001) and hypertensive scores (r = 0.50, p < 0.05), but not with kidney size. Twelve patients (67%) were defined as having CKD stages 2-4. The median concentrating capacity was significantly lower in children within this group, when compared to children with CKD stage 1 possessing a normal eGFR (544 mOsmol/kg, range 413-600 mOsmol/kg vs. 327 mOsmol/kg, range 235-417 mOsmol/l, p < 0.001).

CONCLUSIONS

Impaired kidney concentrating capacity is present in most children with ARPKD and is associated with decreased eGFR and hypertension. A higher resolution version of the Graphical abstract is available as Supplementary information.

Reflux nephropathy and scarring nephropathy: So close and yet so different

OBJECTIVES

Reflux nephropathy is a radiologic condition commonly used to express the existence of renal morphological lesions in patients who have or had vesicoureteral reflux (VUR). This morphological concept is used based on the image data collected, without conducting basic complementary renal function studies. The present study was designed to demonstrate that patients with active VUR present different functional renal alterations from those shown by patients with disappeared VUR.

METHODS

Longitudinal descriptive retrospective analysis including 89 children (46M, 43F) with VUR diagnosis through a standard voiding cystourethrogram (VCUG). The basic renal function tests collected were the maximum urinary osmolality (UOsm) and the urinary albumin/creatinine and NAG/creatinine ratios. The data collected corresponded to two moments, when VUR was diagnosed and when it had already disappeared.

RESULTS

Quantitative differences were verified in the three functional parameters when comparing those corresponding to both moments of the study. In the qualitative analysis, in relation to the intensity of the VUR, differences were observed in UOsm at diagnosis and in the albumin/creatinine ratio once the VUR had cured. At this last moment, a significant increase in the albumin/creatinine ratio was observed in patients with loss of renal parenchyma in relation to those without residual morphological lesions.

CONCLUSIONS

Concentrating ability defect is the most frequent finding in children with active reflux (true reflux nephropathy), whereas the most frequent functional disturbance found, once VUR has cured, is an increase in urinary albumin excretion, related to parenchymal damage. The term dysplastic-scarring nephropathy, could be more appropriate for patients with residual morphological lesions and impaired renal function, once VUR is cured.

Urinary N-Acetyl-β-d-Glucosaminidase (NAG) Levels and Risk of Cardiovascular Events in Diabetic Patients

BACKGROUND

Cardiovascular diseases (CVDs) have a high incidence rate in population with diabetic patients. Studies on the association between urinary N-acetyl-β-d-glucosaminidase (NAG) levels, the biomarker of renal tubular damage, with cardiovascular (CV) events diabetic patients was still few.

METHODS

The relationship between urinary NAG levels and CV events was analyzed in a prospective cohort including 357 patients with type 2 diabetes mellitus at a follow-up of 5 years.

RESULTS

Twenty-six (7.3%) patients have CV events. Kaplan-Meier analysis suggested that diabetic patients with urine NAG levels ≥37.5 IU/L had a higher rate of CV events than those with urine NAG levels <37.5 IU/L (Log rank test, P = 0.021). Cox analysis revealed that elevated urine NAG levels significantly contributed to increased risk of CV events (HR = 1.43, 95% CI 1.23-1.93, P < 0.001) after adjusting for clinical confounding factors. Interestingly, we also found that "abnormal renal function" has an effect modification on the association between urine NAG levels and CV events. ROC-AUC analysis suggested that the urine NAG (AUC = 0.81, P < 0.001) had a better predictive value than eGFR (AUC = 0.74, P = 0.012).

CONCLUSION

Elevated urine NAG levels are associated with higher risk of CV events in patients with type 2 diabetes. These results might further suggested that urinary NAG is a value urinary biomarker for early detecting CV events among diabetic patients.

[Reflux nephropathy and scarring nephropathy: So close and yet so different]

OBJECTIVES

Reflux nephropathy is a radiologic condition commonly used to express the existence of renal morphological lesions in patients who have or had vesicoureteral reflux (VUR). This morphological concept is used based on the image data collected, without conducting basic complementary renal function studies. The present study was designed to demonstrate that patients with active VUR present different functional renal alterations from those shown by patients with disappeared VUR.

PATIENTS AND METHODS

Longitudinal descriptive retrospective analysis including 89 children (46M, 43F) with VUR diagnosis through a standard voiding cystourethrogram (VCUG). The basic renal function tests collected were the maximum urinary osmolality (UOsm) and the urinary albumin/creatinine and NAG/creatinine ratios. The data collected corresponded to two moments, when VUR was diagnosed and when it had already disappeared.

RESULTS

Quantitative differences were verified in the three functional parameters when comparing those corresponding to both moments of the study. In the qualitative analysis, in relation to the intensity of the VUR, differences were observed in UOsm at diagnosis and in the albumin/creatinine ratio once the VUR had cured. At this last moment, a significant increase in the albumin/creatinine ratio was observed in patients with loss of renal parenchyma in relation to those without residual morphological lesions.

CONCLUSIONS

Concentrating ability defect is the most frequent finding in children with active reflux (true reflux nephropathy), whereas the most frequent functional disturbance found, once VUR has cured, is an increase in urinary albumin excretion, related to parenchymal damage. The term dysplastic-scarring nephropathy, could be more appropriate for patients with residual morphological lesions and impaired renal function, once VUR is cured.

Risk factors for kidney scarring and vesicoureteral reflux in 421 children after their first acute pyelonephritis, and appraisal of international guidelines

BACKGROUND

Acute pyelonephritis (AP) is a common bacterial infection in childhood. Follow-up guidelines on these children are controversial. This study aimed to identify risk factors for kidney scarring and vesicoureteral reflux (VUR). Furthermore, international follow-up guidelines were used for simulation to evaluate sensitivity and specificity.

METHODS

Urinary culture-confirmed first-time AP patients (aged 0-14 years) were enrolled (n = 421) from review of patient charts. All underwent kidney ultrasound (US) and a technetium-99m-dimercaptosuccinic acid (DMSA) scan or technetium-99m-mercaptoacetyltriglycine scinti-renography (MAG3) at 4-6 months of follow-up. The international guidelines used for simulation were from the National Institute of Health UK (NICE), the American Association of Paediatrics (AAP) and the Swedish Paediatric Society (SPS).

RESULTS

17.8% presented with an abnormal DMSA/MAG3 at follow-up, 7.1% were diagnosed with VUR grades III-V and 4.7% were admitted for surgery. Non-Escherichia coli infections, abnormal kidney US, elevated creatinine and delayed response to treatment (>48 h) were risk factors for abnormal DMSA findings and VUR grades III-V. NICE and SPS guidelines showed best sensitivity in diagnosing VUR grades III-V (75%) compared with AAP (56%).

CONCLUSIONS

Risk factors are helpful in identifying the children in need of further investigations and minimizing invasive work-up for the rest. International guidelines on follow-up detect a varying number of children with kidney damage and/or significant VUR. Future work must focus on identifying more specific risk factors, better imaging, or specific biomarkers, to enhance sensitivity and specificity in detecting the children at high risk for developing recurrent infections and/or nephropathy.

The use of urinary osmolality to evaluate postoperative renal function in children with ureteropelvic junction obstruction

INTRODUCTION

Split renal function measured in a diuretic renogram is the most popular tool in initial assessment and follow-up of patients with ureteropelvic junction obstruction (UPJO). This study aims to evaluate the use of maximum urinary osmolality after desmopressin administration (DDAVP) to detect renal dysfunction.

PATIENTS AND METHODS

56 children (33 males, 23 females) diagnosed with UPJO underwent quantification of the maximum urinary osmolality (UOsm) at diagnosis. 41 of these children (28 males, 13 females) underwent surgery for UPJO and quantification of the UOsm before and after the surgical intervention (six to 18 months postoperatively) and were included in this longitudinal study.

RESULTS AND DISCUSSION

At diagnosis, UOsm measured after desmopressin administration was abnormal in 64% of patients. After surgical intervention, this rate decreased to 53%. At initial assessment, high creatinine levels were found in 32% of infants younger than one year of age. Albumin/Cr and NAG/Cr ratios were elevated in 12% and 7% of cases, respectively. After surgical intervention, an improvement in the NAG/creatinine ratio and creatinine levels was observed. Preoperative split renal function of the affected kidney was less than 45% in 39% of cases, normal in 44%, and greater than 55% in 17%; in these three subgroups, no differences in renal function markers were found.

CONCLUSIONS

The most sensitive parameter to detect alterations in renal function in children with UPJO is the UOsm and, therefore, the most useful in the follow-up after surgery. No correlation was found between other functional and morphological parameters obtained on renal ultrasound and renogram.