Assessment of urinary protein excretion in the adolescent: effect of body position and exercise

Renal Function Impairment in Children With Congenital Cytomegalovirus Infection: A Cross-sectional Study

BACKGROUND

We aimed to determine the prevalence and severity of glomerular and tubular renal dysfunction by means of urinalysis in infants and toddlers with congenital cytomegalovirus infection (cCMV) and their association with cCMV disease, viruria and antiviral treatment.

METHODS

This cross-sectional study was done using the Spanish Registry of Congenital Cytomegalovirus Infection. First-morning urine samples were collected from January 2016 to December 2018 from patients <5 years old enrolled in Spanish Registry of Congenital Cytomegalovirus Infection. Samples were excluded in case of fever or other signs or symptoms consistent with acute infection, bacteriuria or bacterial growth in urine culture. Urinary protein/creatinine and albumin/creatinine ratios, urinary beta-2-microglobulin levels, hematuria and CMV viruria were determined. A 0.4 cutoff in the urinary albumin/protein ratio was used to define tubular (<0.4) or glomerular (>0.4) proteinuria. Signs and symptoms of cCMV at birth, the use of antivirals and cCMV-associated sequelae at last available follow-up were obtained from Spanish Registry of Congenital Cytomegalovirus Infection.

RESULTS

Seventy-seven patients (37 females, 48.1%; median [interquartile range] age: 14.0 [4.4-36.2] months) were included. Symptom-free elevated urinary protein/creatinine and albumin/creatinine ratios were observed in 37.5% and 41.9% of patients, respectively, with tubular proteinuria prevailing (88.3%) over glomerular proteinuria (11.6%). Proteinuria in the nephrotic range was not observed in any patients. In multivariate analysis, female gender was the only risk factor for tubular proteinuria (adjusted odds ratio = 3.339, 95% confidence interval: 1.086-10.268; P = 0.035). cCMV disease at birth, long-term sequelae, viruria or the use of antivirals were not associated with urinalysis findings.

CONCLUSIONS

Mild nonsymptomatic tubular proteinuria affects approximately 40% of infants and toddlers with mostly symptomatic cCMV in the first 5 years of life.

Evaluation of Proteinuria and Hematuria in Ambulatory Setting

Proteinuria and/or hematuria are common findings in ambulatory settings. Proteinuria can be glomerular and/or tubular in origin and it may be transient, orthostatic, or persistent. Persistent proteinuria may be indicative of a serious kidney pathology. Hematuria, which denotes the presence of an increased number of red blood cells in the urine, can be gross or microscopic. Hematuria can originate from the glomeruli or other sites of the urinary tract. Asymptomatic microscopic hematuria or mild proteinuria in an otherwise healthy child is less likely to be of clinical significance. However, the presence of both requires further workup and careful monitoring.

Assessment of renal function in obese and overweight children with NGAL and KIM-1 biomarkers

Introduction

Aim and background: the incidence of obesity has increased among children, and obesity has been considered an independent risk factor for chronic kidney disease. We aimed to determine the degree of kidney function impairment by evaluating urine neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) levels. Materials and methods: in total, 15 obese, 26 overweight, and 26 control adolescents aged 10 to 16 years were enrolled into the study. Urine samples were evaluated for NGAL and KIM-1 levels using enzyme-linked immunosorbent assay kits. We investigated the association between obesity and related comorbidities with urinary NGAL and KIM-1 excretion. Results: no significant differences were noted between the obese, overweight, and control groups in urinary NGAL and KIM-1 excretion (p = 0.327 and p = 0.917, respectively). In the obese and overweight groups urinary NGAL levels were 50.39 [30.88-74.22] in females and 26.67 [23.24-45.59] in males (p = 0.013). Also, urinary NGAL levels were increased in obese and overweight adolescents with LDL dyslipidemia at 64.12 [30.98-114.32] as compared to those without LDL dyslipidemia: 39.51 [25.59.56.37] (p = 0.024). Furthermore, a correlation was observed between insulin and homeostasis model assessment of insulin resistance levels with the NGAL/creatinine ratio in the overweight group (r = 0.515; p = 0.008, and r = 0.483; p = 0.014, respectively). Such correlation was not found in the obese group. Conclusion: the effect of obesity on renal function could not be determined in children. A longer exposure may be required for obesity-induced disruption of renal function in children. Renal function may be disrupted by dyslipidemia in obese adolescents. Furthermore, obesity impaired renal function in female adolescents. The normalization of these urinary markers as related to urine creatinine should be discussed.

Proteinuria in Children

Although the American Academy of Pediatrics (AAP) removed the screening urinalysis from its health supervision guidelines in 2007, the use of the urinalysis remains an important part of pediatric care. Thus, the incidental finding of proteinuria is still commonplace when a urine sample is collected for various complaints, such as fever and abdominal pain. Knowing when to reassure a patient with proteinuria versus when to perform additional testing is a situation that general practitioners face regularly, but also one that not all may be comfortable dealing with due to the possibility of missing a diagnosis. In addition, proteinuria in certain conditions can signify renal disease and worse outcomes, so general practitioners should know how to screen and interpret the results. Understanding the common benign and pathological causes of proteinuria helps medical providers to better inform and treat their patients, and possibly avoid unnecessary additional testing or subspecialty referrals. [Pediatr Ann. 2020;49(6):e268-e272.].

Hematuria and Proteinuria in Children

Practice Gap

Pediatricians must be aware of screening indications and the evaluation

and management of a child with hematuria and/or proteinuria.

Objectives

After completing this article, readers should be able to:

1. Understand the common causes of proteinuria and hematuria and be able to differentiate between benign and serious causes.

2. Describe screening techniques for initial evaluation of hematuria and proteinuria.

3. Recognize the criteria for diagnosis of proteinuria and hematuria.

4. Plan the appropriate initial evaluation for hematuria and proteinuria and interpret laboratory findings essential for diagnosis.

5. Recognize serious causes of hematuria and proteinuria that warrant immediate referral.

Albuminuria, Proteinuria, and Renal Disease Progression in Children with CKD

BACKGROUND AND OBJECTIVES

The role of albuminuria as an indicator of progression has not been investigated in children with CKD in the absence of diabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Children were enrolled from 49 centers of the CKD in Children study between January of 2005 and March of 2014. Cross-sectional multivariable linear regression (n=647) was used to examine the relationship between urine protein-to-creatinine (UP/C [milligrams per milligram]) and albumin-to-creatinine (ACR [milligrams per gram]) with eGFR (milliliters per minute per 1.73 m2). Parametric time-to-event analysis (n=751) was used to assess the association of UP/C, ACR, and urine nonalbumin-to-creatinine (Unon-alb/cr [milligrams per gram]) on the time to the composite endpoint of initiation of RRT or 50% decline in eGFR.

RESULTS

The median follow-up time was 3.4 years and 202 individuals experienced the event. Participants with a UP/C≥0.2 mg/mg and ACR≥30 mg/g had a mean eGFR that was 16 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. Individuals with ACR<30 mg/g, but a UP/C≥0.2 mg/mg, had a mean eGFR that was 9.3 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. When categories of ACR and Unon-alb/cr were created on the basis of clinically meaningful cutoff values of UP/C with the same sample sizes for comparison, the relative times (RTs) to the composite end-point were almost identical when comparing the middle (RT=0.31 for UP/C [0.2-2.0 mg/mg], RT=0.38 for ACR [56-1333 mg/g], RT=0.31 for Unon-alb/cr [118-715 mg/g]) and the highest (RT=0.08 for UP/C [>2.0 mg/mg], RT=0.09 for ACR [>1333 mg/g], RT=0.07 for Unon-alb/cr [>715 mg/g]) levels to the lowest levels. A similar trend was seen when categories were created on the basis of clinically meaningful cutoff values of ACR (<30, 30-300, >300 mg/g).

CONCLUSIONS

In children with CKD without diabetes, the utility of an initial UP/C, ACR, and Unon-alb/cr for characterizing progression is similar.

Novel urinary tubular injury markers reveal an evidence of underlying kidney injury in children with reduced left ventricular systolic function: a pilot study

BACKGROUND

Evolving data suggest tubular injury markers (TIM) to be diagnostic and prognostic biomarkers of kidney injury in adults with chronic cardiac dysfunction. Such data are not well delineated in asymptomatic children with cardiomyopathy. This study sought to evaluate kidney involvement in children with left ventricular (LV) systolic dysfunction.

METHODS

We conducted a cross-sectional case-control study in 61 asymptomatic children (aged 1.7-21.9 years) with dilated cardiomyopathy (DCM) and LV ejection fraction (LVEF) < 55 %. Routine conventional kidney function markers and the following urinary TIM were measured: KIM-1, IL-18, neutrophil gelatinase-associated lipocalin (NGAL), and L-FABP. Characteristics and TIM data of cases were compared with those of 61 age- and gender-matched healthy controls.

RESULTS

Children with DCM had higher TIM concentrations compared with controls for IL-18 (28.2 pg/mg, IQR [15.9-42.5] vs19.0 [12.6-28.6], p < 0.001), NGAL (13.2 ng/mg [6.5-44.3] vs 8.3 [3.1-17.5], p = 0.01), and KIM-1 (386 pg/mg (248-597) vs 307 [182-432], p = 0.02). All conventional kidney function markers were within normal limits in the DCM cohort. A combined model using cut-off values of KIM-1 ≥ 235, IL-18 ≥ 17.5, and (BNP) > 15 pg/ml resulted in distinction between patients with mildly depressed LV (55 > LVEF ≥ 45) and those with LVEF < 45 %. The sensitivity of this model was ≥80 % when any of the cut-off values was met and specificity 83 % when all cut-off values were met.

CONCLUSIONS

Our data suggest that asymptomatic children with LVEF < 55 % might have subclinical kidney injury that cannot be detected with conventional kidney function markers. TIM in conjunction with other cardiac function markers may be utilized to distinguish asymptomatic children with DCM and moderate or worse LV dysfunction (LFEV < 45 %) from those with mild LV dysfunction (55 > LVEF ≥ 45 %).

Renal biopsy criterion in children with asymptomatic constant isolated proteinuria

BACKGROUND

The criterion of a renal biopsy in children with asymptomatic persistent isolated proteinuria is controversial.

METHODS

To determine an adequate renal biopsy criterion in children with asymptomatic constant isolated proteinuria, the optimal cutoff maximum urinary protein/creatinine ratio (uP/Cr) to separate minor glomerular abnormalities (MGA) and other significant glomerular changes was obtained by receiver operating characteristic analysis in 44 children with asymptomatic constant isolated proteinuria (uP/Cr ≥ 0.2 g/g) screened from 1167 patients who underwent a renal biopsy between September 2000 and April 2010. Patients were divided into two groups according to the cutoff value to verify its validity.

RESULTS

The optimal uP/Cr was 0.5 g/g. In Group 1 (uP/Cr <0.5 g/g, n = 15), only one patient (6.7%) showed focal segmental glomerulosclerosis (FSGS) and the other 14 patients (93.3%) had MGA. In Group 2 (uP/Cr ≥ 0.5 g/g at least once before biopsy, n = 29), 5 patients showed FSGS and 7 patients had nephritis such as IgA nephropathy (41.4%, n = 12) and the other 17 patients (58.6%) showed MGA. These findings indicated that the ratio of non-MGA/MGA was significantly higher in Group 2 than that in Group 1 (P = 0.016) and that if renal biopsies were performed with a criterion of a maximum uP/Cr ≥ 0.5 g/g (criterion for Group 2), renal biopsies could be avoided in 45.2% of patients with MGA. One patient with FSGS in Group 1 showed proteinuria with uP/Cr ≥ 0.5 g/g in the clinical course.

CONCLUSIONS

An adequate renal biopsy criterion in children with asymptomatic constant isolated proteinuria is uP/Cr ≥ 0.5 g/g.

Protein-osmolality ratio for quantification of proteinuria in children

Proteinuria is an important factor for renal injury and prognosis in many diseases. The most valuable method for evaluation of proteinuria is quantitative protein analysis in appropriately 24-h collected urine. But urine collection is difficult and cumbersome especially in children and working adults. The aim of the present study is to define the usefulness of urinary protein/urine osmolality (Uprot/Uosm) ratio in quantification of proteinuria. One hundred and seventy-one patients whose age ranged between 3 and 14 years were included in the study. Uprot/Uosm (r = 0.85, P < 0.001) and urinary protein/creatinine Uprot/Ucrea (r = 0.81 and P < 0.001) ratios were significantly correlated with 24-h protein excretion. Twenty-four-hour protein excretion was correlated with Uprot/Ucrea (r = 0.76, P < 0.001) and Uprot/Uosm (r = 0.79, P < 0.001) ratios in proteinuric group. But, there was no correlation between Uprot/Uosm and Uprot/Ucrea ratios with 24-h protein excretion in non-proteinuric group. The positive and negative predictive value of Uprot/Uosm ratio of 0.28 mg/l/mOsm/kg was 89.9 and 90.8% and Uprot/Ucrea ratio of 0.24 mg/mg was 85.7 and 90% for estimating proteinuria (above 4 mg/m2 h(-1)). The 95th percentile of Uprot/Uosm ratio was 0.25 mg/l/mOsm/kg and Uprot/Ucrea ratio was 0.27 mg/mg in normal group. The best estimate was Uprot/Uosm ratio of 1.42 (sensitivity 100%, specificity 94.9%) and Uprot/Ucrea ratio of 0.75 (sensitivity 100%, specificity 92.9%) for nephrotic proteinuria (40 mg/m2 h(-1)). Uprot/Uosm which is a reliable and simple method can be used for quantification of proteinuria in pediatric patients with normal renal function. Using Uprot/Uosm ratio for quantification of proteinuria can remove the necessity of 24-h urine collection, urine creatinine measurement and spending additional cost and time if the center measures the urine osmolality routinely in urine analysis.

Reliability of different expert systems for profiling proteinuria in children with kidney diseases

This study was designed to compare three urinary protein expert systems for profiling proteinuria in children with kidney diseases. Freshly voided urine specimens were collected from 61 children with glomerular diseases, 19 children with tubular diseases and 25 healthy children aged 3-16 years. The urinary protein expert systems were: (1) albumin/total protein ratio (APR), (2) alpha-1-microglobulin/alpha-1-microglobulin + albumin algorithm (AAA), and (3) the complex urine protein expert system (UPES, PROTIS) algorithm. APR correctly identified glomerular proteinuria in 47/61 children, tubular proteinuria in 16/19 children and normal proteinuria in 23/25 healthy children. AAA correctly identified glomerular proteinuria in 61/61 children and tubular proteinuria in 18/19 children, and 25/25 healthy children were characterized as having no abnormal proteinuria. AAA was not influenced by the stage of chronic kidney disease. UPES differentiated the type of proteinuria in children with glomerular diseases into glomerular (50/61 patients) and mixed glomerulo-tubular (6/61 patients). Tubular proteinuria was identified in 16/19 patients and described as mixed glomerulo-tubular proteinuria in 3/19 patients. Mixed glomerulo-tubular proteinuria was found only in children with chronic kidney disease stages 2-5 of glomerular and tubular diseases. In conclusion, the AAA and UPES had the highest accuracy levels.

Profiling proteinuria in pediatric patients

This study was designed to characterize proteinuria in children with kidney disease. Random urine samples from 250 pediatric patients were examined by quantitative measures of total protein (pr), albumin (Alb), and creatinine (cr). Patient diagnoses were subjectively categorized as "Glomerular" (GD) or "Tubulo-interstitial" disease (TD) in origin. Proteinuria was quantitated by the random urine protein-to-creatinine (Upr/cr) ratio, and glomerular proteinuria was assessed as the albumin-to-creatinine ratio (Ualb/cr) and percentage albuminuria (%Alb=Alb/pr*100). The non-albumin fraction (1-Alb/pr) includes low-molecular-weight proteins and micro- and macroglobulins. Of the 250 patients, 112 (45%) had GD and 138 (55%) had TD. Both proteinuria and albuminuria correlated with a decline in glomerular filtration rate (GFR) (r=-0.4; p<0.0001). Those with GD averaged significantly greater %Alb than those with TD at all levels of proteinuria (p<0.0001). With loss in GFR, %Alb increased significantly in patients with TD (18+/-13 to 47+/-30%; p<0.001) and GD (56+/-26 to 74+/-15%; p<0.01), respectively. The %Alb at all levels of GFR averaged <50% in those with TD and >50% in those with GD. In conclusion, random Ualb/cr, Upr/cr, and %Alb provide a simple and inexpensive assessment of proteinuria and may profile renal disease activity and response to therapy in pediatric patients.

Proteinuria: potential causes and approach to evaluation

Proteinuria may be associated with a renal or systemic disease, or it may be isolated. The latter occurs in asymptomatic patients without evidence of any disease or abnormality of the urine sediment. Isolated proteinuria may be subdivided into two broad groups: (1) benign forms, with a favorable-to-excellent prognosis and (2) persistent forms, some of which have a worrisome prognosis. Functional proteinuria may occur in disorders with altered renal hemodynamics, usually resolves, and is not associated with progressive renal disease. Idiopathic transient proteinuria is typically discovered on routine screening and usually disappears on subsequent testing. In idiopathic intermittent proteinuria, a significant number (50%) of urine samples exhibit abnormal rates of protein excretion. Although structural abnormalities may be observed on renal biopsy, progressive renal insufficiency is unusual. In orthostatic proteinuria, the rate of protein excretion completely normalizes in the recumbent position. Long-term studies show this to be a benign condition. In persistent isolated proteinuria, at least 80% of random urine samples exhibit abnormal protein excretion. This represents a heterogeneous group, but a significant proportion of these patients have prominent renal pathologic findings and progress to serious renal disease. Proteinuria with significant renal disease may be non-nephrotic or nephrotic range. The former does not exclude glomerular disease, but tubulointerstitial or vascular disorders are also likely when proteinuria is less than 2 g/24 hours. Patients with nephrotic-range proteinuria generally have a glomerular disorder. Distinction between benign and more ominous forms of proteinuria requires careful evaluation.

Evaluation and management of proteinuria and nephrotic syndrome in children: recommendations from a pediatric nephrology panel established at the National Kidney Foundation conference on proteinuria, albuminuria, risk, assessment, detection, and elimination (PARADE)

OBJECTIVE

The development of this review article evolved from a National Kidney Foundation consensus conference on recent advances in the importance of evaluating and treating proteinuria. From this conference, a series of recommendations for the evaluation of adults with proteinuria was published. Because specific pediatric aspects of the problem were outside the scope of the original National Kidney Foundation publication, an ad hoc committee of 6 pediatric nephrologists who were active participants in the National Kidney Foundation conference was established to provide primary care physicians with a concise, up-to-date reference on this subject.

METHODS

The recommendations that are given represent the consensus opinions of the authors. These are based on data from controlled studies in children when available, but many of the opinions are, by necessity, based on uncontrolled series in children or controlled trials performed in adults, because controlled trials in children have not been performed to evaluate many of the treatments described.

RESULTS AND CONCLUSIONS

These recommendations are intended to provide primary care physicians with a useful reference when they are faced with a young child or teenager who presents with proteinuria, whether this is mild and asymptomatic or more severe, leading to nephrotic syndrome.

Evaluation of hematuria, proteinuria, and hypertension in adolescents

Signs or symptoms of renal disease in adolescents deserve prompt attention and appropriate evaluation. Adolescents are susceptible to a variety of urinary tract disorders. The key issue in the evaluation of hematuria or proteinuria in adolescents is the existence of concomitant signs of renal disease. For isolated hematuria or proteinuria, demonstration of persistence and a reasoned evaluation are in order. Hypertension in adolescents must be carefully documented and, when present, considered seriously. The fact that most teens with persistent elevated blood pressures have essential hypertension is still a great concern because for most of these adolescents the hypertension will be lifelong and, if left untreated, can be associated with significant morbidity and mortality in the adult years.

Urinary albumin excretion in Spanish children. Niño Jesus Group

We measured urinary albumin excretion in 2,224 school-children (1,168 boys, 1,056 girls) aged 2-18 years, between 1989 and 1990 to establish reference values. We recorded all pathological antecedents and findings from physical examination, including anthropometric parameters and arterial blood pressure. The analytical study included serum total protein, albumin and creatinine. The second-morning urine and the nightly (rest) 10-h urine sample were collected and we determined the concentration of albumin and creatinine. We found a positive statistically significant correlation between the urinary albumin excretion (micrograms/10 h) and age, height, weight and body surface area. We suggest that it would be useful to relate the urinary albumin excretion to body surface area. The mean value for albumin excretion was 3.49 micrograms/ml in boys and 3.63 micrograms/ml in girls. The urinary albumin/creatinine ratio showed a high correlation with the albumin excretion (r = 0.958).

Post-exercise albuminuria does not predict microalbuminuria in type 1 diabetic patients

To investigate whether post-exercise urinary albumin excretion in Type 1 diabetic children and adolescents may prospectively predict the development of microalbuminuria, we have assessed post-exercise urinary albumin excretion before and after 6.2 +/- 1.7 years of follow-up in 66 diabetic children and adolescents. Post-exercise urinary albumin excretion rose significantly above the pre-exercise values in diabetic patients by 2.7 (-3.8 to 84.2) micrograms min-1 (p < 0.001) and in a group of 9 healthy individuals by 3.9 (-0.7 to 13.7) micrograms min-1 (p < 0.02) without significant differences between groups. Post-exercise albuminuria was greater in postpubertal than prepubertal 9.8 vs 4.3 micrograms min-1 (p < 0.03) and pubertal 9.8 vs 6.0 micrograms min-1 (p < 0.02) patients; post-exercise changes in urinary albumin excretion were also positively related to glycated haemoglobin (r = 0.293; p < 0.05). Eight out of 66 patients developed microalbuminuria at follow-up. Urinary albumin excretion at follow-up was comparable between patients with normal and abnormal post-exercise urinary albumin excretion; moreover post-exercise urinary albumin excretion was within the normal range in 5 out of 8 patients with microalbuminuria at follow-up. In conclusion post-exercise albuminuria does not seem to be a useful predictor of the onset of microalbuminuria in Type 1 diabetic children and adolescents.

Evaluation of variability of proteinuria indices

We compared several indices of proteinuria, namely protein concentration, hourly protein excretion rate (Up/h) and protein/creatinine ratio (Up/Ucr) in single voided urine samples as well as 24 h-urinary protein excretion (24 h-Up), in 44 children, aged 4-16 years, with varying degrees of urinary protein excretion. We found an excellent correlation between Up/h and Up/Ucr in early morning samples. These two indices in early morning samples had excellent correlation with 24 h-Up, comparable to those in any other urine sample of the day. Among daytime samples, Up/h varied widely, in contrast to Up/Ucr, which had significantly less variability. We analysed six early morning and six bedtime samples from 39 of these subjects, and found smaller coefficients of variation for individual patient's indices in morning samples. Up/h was more variable than Up/Ucr, especially in bedtime samples. Urinary protein concentration had a poorer correlation with 24 h-Up and was more variable than any other index. We conclude that the Up/Ucr in early morning samples, which has the advantages both of simplicity and low day-to-day variability in a given patient, is a superior index of proteinuria.