Urinary biomarkers in the early detection and follow-up of tubular injury in childhood urolithiasis

Exploring the Utility of Urinary Creatinine Adjustment for KIM-1, NGAL, and Cystatin C for the Assessment of Kidney Function: Insights from the C-KidnEES Cohort

Normalization of urinary biomarkers of kidney injury is a common practice in clinical and research settings to account for variations in urine concentration, and urinary creatinine is often used as a reference. However, to date, there is no consensus on the adjustment of urinary biomarkers with creatinine, and both absolute and creatinine-adjusted biomarker levels are adopted for making interpretations of kidney health. Hence, the present study aimed to investigate the associations of urinary creatinine with three widely used kidney injury biomarkers, KIM-1, NGAL, and cystatin C, to validate the applicability of urinary creatinine as a reference for normalization. A cross-sectional study was performed with 2100 students, 10-18 years of age in the Children's Kidney Environmental Exposure Study (C-KidnEES) cohort established in Sri Lanka. As identified in linear regression analyses, normalization of urinary KIM-1, NGAL, and Cys-C to urinary creatinine did not result in significant under-adjustment or over-adjustment to the absolute urinary concentrations, giving no specific rationale for creatinine adjustment. Hence, absolute urinary concentrations of the above biomarkers can be adopted for the characterization of subclinical kidney injury in adolescents in community studies where early morning urine sampling is practiced. However, for spot urine samples, consideration of both absolute and creatinine-adjusted biomarker levels would be a better approach.

Current Status of Protein Biomarkers in Urolithiasis-A Review of the Recent Literature

Urolithiasis is an increasingly common clinical problem worldwide. The formation of stones is a combination of metabolic status, environmental factors, family history and many other aspects. It is important to find new ways to quickly detect and assess urolithiasis because it causes sudden, severe pain and often comes back. One way to do this is by exploring new biomarkers. Current advances in proteomic studies provide a great opportunity for breakthroughs in this field. This study focuses on protein biomarkers and their connection to kidney damage and inflammation during urolithiasis.

Normal values for pediatric urinary biochemistry in early infancy

BACKGROUND

Urinary levels of N-acetyl-β-D-glucosaminidase (NAG), α1-microglobulin (α1-MG), and β2-microglobulin (β2-MG) are measured as markers of renal tubular damage. We previously determined normal values for these urine biochemical examinations in healthy children over 3 years old. However, the values are not applicable to children younger than 2 years old, and children less than 1 year old, in particular, seem to show very high levels for all these markers. Hence, as normal values for children below 2 years old remain unclear, we determined the normal values for urinary biochemical markers in this age group.

MATERIAL AND METHODS

Fresh urine samples were obtained from 293 healthy children (from newborns to 2-year-old children). All the samples were subjected to normal urinalysis. NAG, α1-MG, β2-MG, and creatinine (Cr) levels in extracted samples were measured immediately in the central laboratory at Kanazawa Medical Center.

RESULTS

The normal values for each biomarker in children below 2 years of age were determined. Additionally, urinary α1-MG levels were observed to decrease most rapidly with age, almost reaching the level at ≥ 3 years by 6 months after birth.

CONCLUSION

Renal tubular function can be evaluated in children < 3 years old using the normal values. Further, the most stable and useful urinary marker from early infancy seems to be urinary α1-MG.

Can Urinary KIM-1 and NGAL Predict Management Endoscopic Surgery in Acute Unilateral Obstructive Stone Disease? Results from a Prospective Cohort Study

INTRODUCTION

Kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are the leading novel biomarkers used efficiently in acute kidney injury (AKI). The levels of these biomarkers increase especially in the early period of nephrotoxic and ischemic renal damage. In this study, we aimed to investigate the clinical importance of NGAL and KIM-1 biomarkers used in the effective evaluation of kidney functions in patients with acute unilateral obstructive stone disease (AUOSD) in the management of endoscopic surgery.

MATERIALS AND METHODS

We prospectively included patients who underwent endoscopic surgery due to AUOSD between January 2018 and December 2019. Urine KIM-1 and NGAL values of the patients were measured preoperative period, postoperative 4th h, and postoperative 7th day. The patients were evaluated according to the location and size of the stone, the degree of renal hydronephrosis, the duration of the operation, complications, and JJ stent placement.

RESULTS

The study enrolled 50 patients. Urinary KIM-1/Cr and urinary NGAL/Cr ratios were higher in postoperative 4th h than in others (p < 0.001). Also, we found that urinary KIM-1/Cr and urinary NGAL/Cr ratios with Grade 2 and higher hydronephrosis were statistically higher than Grade 0-1 hydronephrosis (p < 0.001 and p: 0.042, respectively). Additionally, a preoperative urinary KIM-1 value of 1.24 ng/mL had a sensitivity of 78% and a specificity of 63% to predict the presence of hydronephrosis. When urine KIM-1 and NGAL results were compared with surgery time, stone size and location, serum creatinine (sCr) value, and Post-Ureteroscopic Lesion Scale grade, the difference was not statistically significant. Postoperative 7th day NGAL/Cr and KIM-1/Cr ratios were statistically higher in those with JJ stents placed (p: 0.03 and p: 0.004, respectively).

CONCLUSION

KIM-1 and NGAL can be used in our assessment of renal function in patients with AUOSD, even if sCr is normal. Also, these biomarkers can predict the presence of hydronephrosis. It can be helpful in determining the time of surgical treatment, as well as providing information in the follow-up of patients with JJ stents after treatment.

Distribution of urinary N-acetyl-beta-D-glucosaminidase and the establishment of reference intervals in healthy adults

BACKGROUND

Urinary N-acetyl-beta-D-glucosaminidase (NAG) plays an important role in the early diagnosis and progression of diseases related to renal tubular injury. We detected the urinary NAG concentration, assessed the preliminary statistics of its distribution, and established reference intervals for healthy adults in China using the rate method.

METHODS

A total of 1,095 reference individuals (aged 20 to 79 years) met the requirements for inclusion in this study. Urinary NAG concentrations were detected using an AU5800 automatic biochemical analyzer with its matched reagents. The Kolmogorov-Smirnov test was used to analyze the normality of the data. According to the guidelines of C28-A3 and WS/T 402-2012, the reference intervals of urinary NAG were established using the nonparametric percentile method (unilateral 95th percentile).

RESULTS

The urinary NAG data showed a non-normal distribution. The distribution of urinary NAG was significantly different by sex and age. Therefore, the reference intervals of urinary NAG were established using the rate method: males (aged 20-59 years) <19.4 U/L (90% CI: 18.0-20.3 U/L); males (aged 60-79 years) <22.3 U/L (90% CI: 20.2-22.6 U/L); females (aged 20-59 years) <15.7 U/L (90% CI: 15.2-16.5 U/L); and females (aged 60-79 years) <21.4 U/L (90% CI: 20.3-22.3 U/L).

CONCLUSIONS

We established preliminary reference intervals of urinary NAG for healthy adults in China to provide guidance for health screening, auxiliary diagnosis, and treatment monitoring of renal tubule-related diseases.

Roles Played by Biomarkers of Kidney Injury in Patients with Upper Urinary Tract Obstruction

Partial or complete obstruction of the urinary tract is a common and challenging urological condition caused by a variety of conditions, including ureteral calculi, ureteral pelvic junction obstruction, ureteral stricture, and malignant ureteral obstruction. The condition, which may develop in patients of any age, induces tubular and interstitial injury followed by inflammatory cell infiltration and interstitial fibrosis, eventually impairing renal function. The serum creatinine level is commonly used to evaluate global renal function but is not sensitive to early changes in the glomerular filtration rate and unilateral renal damage. Biomarkers of acute kidney injury are useful for the early detection and monitoring of kidney injury induced by upper urinary tract obstruction. These markers include levels of neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemotactic protein-1, kidney injury molecule 1, N-acetyl-b-D-glucosaminidase, and vanin-1 in the urine and serum NGAL and cystatin C concentrations. This review summarizes the pathophysiology of kidney injury caused by upper urinary tract obstruction, the roles played by emerging biomarkers of obstructive nephropathy, the mechanisms involved, and the clinical utility and limitations of the biomarkers.

Effects of short-term atorvastatin use in patients with calcium stones: A randomized placebo-controlled clinical trial

PURPOSE

A few experimental and observational studies have reported that atorvastatin prevents calcium oxalate stone formation. Our study is the first to investigate the effect of atorvastatin on 24-hour urinary metabolites, urinary malondialdehyde (U-MDA) (an oxidative stress marker) and urinary neutrophil gelatinase-associated lipocalin (U-NGAL) (a renal tubular injury marker) in patients with calcium stones and hyperoxaluria.

MATERIALS AND METHODS

This randomized, double-blind, placebo-controlled, parallel-group clinical trial included 32 adults with recurrent calcium stone formation and hyperoxaluria. All participants received a 3-month course of either atorvastatin (20 mg/d) or placebo of an identical shape. Both groups received the usual nutritional care based on the European Association of Urology guidelines.

RESULTS

Twenty-eight participants completed the study. Serum levels of total and low-density lipoprotein cholesterol decreased in the atorvastatin group, and these changes were significantly different between groups (p<0.001). No statistically significant differences were observed between intergroup changes of the 24-hour urinary metabolite analysis, the U-MDA to creatinine ratio and the U-NGAL to creatinine ratio.

CONCLUSIONS

Atorvastatin administration at a dose of 20 mg/d for 3 months did not affect 24-hour urinary metabolite, U-MDA and U-NGAL levels in recurrent calcium stone formers. However, this study could not disprove the preventive role of atorvastatin in kidney stone formation. Future studies should consider a larger sample size, longer follow-up, different drug doses, and measurements of multiple biomarkers of oxidative stress and tubular injury.