Prognosis in postural (orthostatic) proteinuria: forty to fifty-year follow-up of six patients after diagnosis by Thomas Addis

Orthostatic proteinuria due to inferior vena cava interruption without nutcracker phenomenon in an old obese female: a case report and literature review

BACKGROUND

Nutcracker syndrome (NCS) caused by left renal vein (LRV) entrapment, is one of the most common causes of orthostatic proteinuria. In stereotype, orthostatic proteinuria is often accompanied by left renal vein obstruction and is found in young and underweight individuals. Here, we report a rare case with orthostatic proteinuria in an old obese female caused by a rare type of congenital inferior vena cava (IVC) interruption.

CASE PRESENTATION

A 65-year-old obese woman, who suffered from fluctuated proteinuria, had been misdiagnosed as chronic glomerulitis for 30 years. Instead of having any sign of NCS, she had a unique type of IVC interruption. Most venous blood from infrarenal IVC and right kidney drained into her LRV, and then through the expanded communicating vessel, drained into the left ascending lumbar vein which extended as hemiazygos vein. To the best of our knowledge, this is one of the first cases reported of orthostatic proteinuria attributed to the subsequent hemodynamic irregularity caused by IVC interruption without nutcracker phenomenon.

CONCLUSION

Adult-onset orthostatic proteinuria is relatively rare, hard to be recognized and could be misdiagnosed as chronic glomerulonephritis. The case provided a novel differential diagnostic condition for those who suffered from fluctuated proteinuria of unknown causes.

Increase in suicide following an initial decline during the COVID-19 pandemic in Japan

There is increasing concern that the coronavirus disease 2019 (COVID-19) pandemic could harm psychological health and exacerbate suicide risk. Here, based on month-level records of suicides covering the entire Japanese population in 1,848 administrative units, we assessed whether suicide mortality changed during the pandemic. Using difference-in-difference estimation, we found that monthly suicide rates declined by 14% during the first 5 months of the pandemic (February to June 2020). This could be due to a number of complex reasons, including the government's generous subsidies, reduced working hours and school closure. By contrast, monthly suicide rates increased by 16% during the second wave (July to October 2020), with a larger increase among females (37%) and children and adolescents (49%). Although adverse impacts of the COVID-19 pandemic may remain in the long term, its modifiers (such as government subsidies) may not be sustained. Thus, effective suicide prevention-particularly among vulnerable populations-should be an important public health consideration.

Orthostatic proteinuria: an overestimated phenomenon?

BACKGROUND

Although orthostatic proteinuria (OP) is the most common cause of childhood proteinuria, excluding transient proteinuria, data regarding prevalence and long-term prognosis are limited. We aimed to determine prevalence of OP in healthy schoolchildren evaluating relationships with age, gender and body mass index, and determine follow-up.

METHODS

A total of 1701 healthy children aged 6-15 years were selected using a population-based, stratified, cluster-sampling method; and random urine samples were taken. For proteinuria ≥ 1+ in first urine samples, second and third random samples were taken at least 2 weeks apart to exclude transient proteinuria. For continuing proteinuria after third samples, first morning urine samples were collected. Cases where proteinuria was not detected in first morning urine samples were diagnosed as OP.

RESULTS

Sixty-four of 1701 children (3.7%) had proteinuria on first random urine samples. After second and third urine samples, proteinuria persisted in only 16 (0.94%). OP was detected in 11 (0.65%). Prevalence of OP tended to decrease with increasing BMI, though not statistically significant. All 7 cases with OP who were re-evaluated later, had no proteinuria 3 years after diagnosis.

CONCLUSIONS

Prevalence of OP in our study was lower than the literature. At least three random urine samples should be taken to exclude transient proteinuria in an asymptomatic child/adolescent before making a diagnosis of OP using first morning urine samples. OP is a benign condition and resolves spontaneously in most cases. Underweight children had a tendency for OP compared with overweight and obese children; however, further studies with larger number of patients are needed.

Proteinuria-take a closer look!

Proteinuria is a hallmark of kidney disease. Therefore, measurement of urine protein content plays a central role in any diagnostic work-up for kidney disease. In many cases, proteinuria analysis is restricted to the measurement of total protein content knowing that very high levels of proteinuria (nephrotic proteinuria) are characteristic of glomerular disease. Still, proteinuria can also be a manifestation of impaired tubular protein reabsorption or even be physiological. This review will discuss the physiology of renal protein handling and give guidance on a more sophisticated analysis of proteinuria differentiating albumin, low-molecular weight proteins and immunoglobulins. These non-invasive tests are available in most routine clinical laboratories and may guide the clinician in the diagnostic process before ordering far more expensive (molecular genetic testing) and/or invasive (kidney biopsy) diagnostics.

Personalized medicine in diabetic kidney disease: a novel approach to improve trial design and patient outcomes

PURPOSE OF REVIEW

In the last decade many attempts have been made to reduce the high residual risk of end-stage kidney disease and cardiovascular disease in patients with diabetic kidney disease by targeting a variety of risk markers. Subsequent analyses revealed that the variation in individual drug response to the tested interventions partly explains why these trials did not result in additional kidney or cardiovascular protection. This review summarizes recent insights regarding individual variation in drug response. Additionally, we explore novel approaches to incorporate this drug response variability in the design of new clinical trials.

RECENT FINDINGS

Recent studies suggest that a plausible explanation for individual therapy resistance emanates from intrinsic individual characteristics such as genetic make-up or volume status and is likely only partially explained by drug characteristics such as the dose or type of intervention. Biomarker-based enrichment strategies to identify high-risk individuals and/or those who are more likely to respond to interventions offer opportunities to tailor therapies to individual patients.

SUMMARY

Individual drug response variability is a recognized phenomenon in clinical practice. It is time to implement novel approaches that take into account this response variability in the design of new trials in diabetic kidney disease in order to define optimal therapies for individual patients.

Simplified Algorithm for Evaluation of Proteinuria in Clinical Practice: How should A Clinician Approach?

Background

Proteinuria is a common laboratory finding among children and adolescents. It can be identified as either a transient or a persistent finding and can represent a benign condition or a serious disease.

Methods

Pertinent medical literature for asymptomatic proteinuria in children and adolescents published in English was searched between January 1980 and May 2017 using PubMed, MEDLINE, EMBASE, and Google Scholar research databases. Of the 64 reviewed articles, 24 studies were eligible for inclusion.

Results

Random spot urine protein-to-creatinine (PCR) ratio is widely used to reliably detect proteinuria. The normal value for the spot PCR in children aged 2 years or older is less than 0.3. In children aged below 2 years, the PCR can be as high as 0.5. Orthostatic proteinuria is defined as urine PCR greater than 0.3 detected in a urine specimen during the daytime activity but less than 0.3 on the first morning void specimen. PCR above 3.0 signifies heavy proteinuria as seen in nephrotic syndrome. Orthostatic proteinuria is a frequent cause of proteinuria in asymptomatic children and adolescents, which require no specific therapy except for health maintenance follow-up. Pediatric nephrologist referral is indicated when the proteinuria is constant and persists over 6 months or is associated with hematuria, hypertension, or renal dysfunction.

Conclusions

We provide a simplified diagnostic algorithm for evaluation of proteinuria in primary care adolescents who appear well and in whom proteinuria is incidentally discovered during a routine examination.

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.

Trends in Albuminuria and GFR Among Adolescents in the United States, 1988-2014

RATIONALE & OBJECTIVE

Albuminuria and low estimated glomerular filtration rate (eGFR) define chronic kidney disease in adults and youth. Different from adults, the burden of abnormal kidney markers among youth in the general United States population is largely unknown.

STUDY DESIGN

Serial cross-sectional national surveys.

SETTING & PARTICIPANTS

Adolescents aged 12 to 18 years participating in the National Health and Nutrition Examination Surveys 1988 to 2014. Surveys were grouped into three 6-year periods.

PREDICTORS

Demographic and clinical determinants of kidney markers.

OUTCOME

Prevalence and trends in persistent albuminuria, low (< 60mL/min/1.73m²) and reduced (< 90mL/min/1.73m²) eGFRs.

ANALYTICAL APPROACH

Outcomes defined as persistent albumin-creatinine ratio ≥ 30mg/g (persistent albuminuria), eGFR < 90mL/min/1.73m² (reduced kidney function), and eGFR < 60mL/min/1.73m² (low kidney function). Multiple imputation analysis was used to estimate missing follow-up values of albuminuria.

RESULTS

Prevalences of persistent albuminuria were 3.64% (95% CI, 1.82%-5.46%) in 1988-1994 and 3.29% (95% CI, 1.94%-4.63%) in 2009-2014 (adjusted prevalence ratio, 0.93; 95% CI, 0.53-1.62; P=0.8 for trend). Prevalences of reduced eGFR were 31.46% (95% CI, 28.42%-34.67%) and 34.58% (95% CI, 32.07%-37.18%), respectively (adjusted prevalence ratio, 1.21; 95% CI, 1.00-1.46; P < 0.001 for trend). Prevalences of low eGFR were 0.32% (95% CI, 0.12%-0.84%) in 1988-1994 and 0.91% (95% CI, 0.58%-1.42%) in 2009-2014 (adjusted prevalence ratio, 3.10; 95% CI, 1.10-9.01; P = 0.09 for trend). Prevalences of albuminuria and/or low eGFR remained at 4.0% in 1988-1994 and 2009-2014 (adjusted prevalence ratio, 1.06; 95% CI, 0.64-1.77; P = 0.8 for trend).

LIMITATIONS

Persistent albuminuria data were based on imputed values (for second assessment of albuminuria) in 91% of participants; lack of second eGFR assessment to confirm sustained reduction in kidney function.

CONCLUSIONS

Albuminuria prevalence has not changed significantly in the US adolescent population between 1988 and 2014. Prevalences of both reduced and low eGFRs were higher in the most recent study period; however, < 1% of adolescents had low eGFRs.

Variability in response to albuminuria-lowering drugs: true or random?

AIMS

Albuminuria-lowering drugs have shown different effect size in different individuals. Since urine albumin levels are known to vary considerably from day-to-day, we questioned whether the between-individual variability in albuminuria response after therapy initiation reflects a random variability or a true response variation to treatment. In addition, we questioned whether the response variability is drug dependent.

METHODS

To determine whether the response to treatment is random or a true drug response, we correlated in six clinical trials the change in albuminuria during placebo or active treatment (on-treatment) with the change in albuminuria during wash-out (off-treatment). If these responses correlate during active treatment, it suggests that at least part of the response variability can be attributed to drug response variability. We tested this for enalapril, losartan, aliskiren, atrasentan and paricalcitol.

RESULTS

No correlation between the on- and off-treatment albuminuria change was observed in the placebo arm of all clinical trials (R²  < 0.01). However, we observed significant associations between the on- and off-treatment response (R² 0.14 to 0.57; all P < 0.015) for different albuminuria lowering drugs. Additionally, the albuminuria responses strongly correlated when the same individual was re-exposed to the same drug at the same dose: lisinopril 10 mg day^-1 (R²  = 53%; P < 0.01), losartan 50 mg day^-1 (R²  = 63%; P < 0.01).

CONCLUSION

The degree of albuminuria lowering with antialbuminuric drugs varies between patients. This variability in response appears drug-class independent. Identifying which factors determine this initial short-term variation in drug response appears important since the degree of albuminuria lowering is related to subsequent long-term renoprotection.

Urinalysis in children and adolescents

BACKGROUND

Urinalysis is the most commonly performed biochemical test in infancy and early childhood. The urine sample should be correctly obtained, age-specific aspects should be considered, and age-dependent reference values should be used.

METHOD

This review is based on a selective literature search in electronic databases, textbooks, and guidelines from Germany and abroad on the acquisition of urine samples and the performance of urinalysis in infancy and early childhood.

RESULTS

The timing and mode of acquisition of the urine sample affect the assessment of hematuria, proteinuria, leukocyturia, nitrituria, and the uropathogenic bacterial colony count in the urine culture. Dipstick tests can be used for targeted screening for these features. The test results should be interpreted together with the findings of urine microscopy, the medical history, and the physical examination. Proteinuria should be quantified and differentiated; both of these things can be done either from collected urine or (especially in infants and young children) from a spontaneously voided urine sample, by determination of the protein/creatinine quotient. Orthostatic proteinuria in an adolescent requires no further evaluation or treatment. Hematuria should be characterized as either glomerular or non-glomerular erythrocyturia. Asymptomatic, isolated microhematuria in childhood is not uncommon and often transient; in the absence of a family history, it usually does not require an extensive work-up. Proteinuria combined with hematuria should arouse the suspicion of glomerulonephritis.

CONCLUSION

Urinalysis in infancy and early childhood is a simple and informative diagnostic test as long as the urine sample has been obtained properly and the results are interpreted appropriately for this age group.

Diabetic kidney disease in children and adolescents

Diabetes, more frequently type 1, but increasingly also type 2, commonly occurs in childhood. While more advanced diabetic kidney disease (DKD), e.g., loss of glomerular filtration rate (GFR), does not occur until adulthood, kidney biopsies show DKD structural changes as early as 1.5-5 years after the onset of type 1 diabetes. Earliest clinical sign of DKD, increased urine albumin excretion, commonly appears during childhood and adolescence and presents an important opportunity to detect and intervene in early DKD, perhaps more successfully than later in the disease course. Longitudinal studies of type 1 diabetes have enriched our understanding of the DKD natural history and modifiable risk factors for DKD progression. These studies have also shown that the presence of DKD marks a subset of people with diabetes who are at the highest risk of early mortality, supporting an enhanced focus on DKD detection, prevention, and treatment. Early studies suggest that youth-onset type 2 diabetes is associated with a higher prevalence of comorbidities and risk factors and follows a more aggressive natural history. A deeper understanding of the natural history, risk factors, underlying mechanisms and therapeutic options for DKD in young-onset type 2 diabetes awaits further studies.

Should screening of renal markers be recommended in a working population?

INTRODUCTION

It is debated whether the general population should be screened for kidney disease. This study evaluated whether screening of albuminuria and estimated glomerular filtration rate (eGFR) in a working population should be recommended to detect subjects with chronic kidney disease.

METHODS

The unreferred renal insufficiency study is a cross-sectional study in 1,398 workers aged 17-65. Markers of cardiovascular and renal disease were measured. Cardiovascular risk (CVR) was defined by hypertension (n = 416), diabetes (n = 45), dyslipidemia (n = 159) and/or history of a cardiovascular event (n = 10).

RESULTS

In our population, 5 % of the workers had microalbuminuria, 0.5 % had macroalbuminuria and <0.1 % had eGFR <60 ml/min/1.73 m(2). All workers with an eGFR <60 ml/min/1.73 m(2) and/or macroalbuminuria (8/8) had at least one CVR factor, whereas this was the case in only half of workers with microalbuminuria (36/73, p = 0.007). In workers without CVR factors, the presence of microalbuminuria was associated with low body mass index (BMI, p < 0.001) or physiochemical exposure risk (p < 0.001).

CONCLUSIONS

Screening of renal markers in a working population, identified only a few subjects with an eGFR <60 ml/min/1.73 m(2) or macroalbuminuria. Although microalbuminuria was more prevalent, it might not necessarily indicate kidney disease, as it may have a completely different meanings depending of the phenotype of the screened subjects. Besides underlying CVR factors, microalbuminuria was also associated with low BMI in absence of any risk factor, suggesting presence of benign postural proteinuria. In addition, microalbuminuria also seemed to be related to physicochemical exposure. In view of the impossibility to further analyze this finding in the present study, the meaning of this observation needs to be further investigated.

Microalbuminuria: causes and implications

Management strategies are increasingly focused on tackling the increasing burden of cardiovascular disease worldwide. Microalbuminuria is a powerful predictor of cardiovascular disease and mortality in adults. This holds true in the general adult population but is particularly recognized in those with diabetes, where it identifies those likely to develop progressive atherosclerotic vascular disease and renal impairment. The atherosclerotic process begins in childhood with likely consequences in later life. In-depth understanding of the mechanisms through which microalbuminuria occurs holds promise for designing therapies to arrest its development in the future. Microalbuminuria arises from increased leakage of albumin through the complex glomerular sieve known as the glomerular filtration barrier. This requires changes in the physio-chemical properties of components of this barrier. However, the increased glomerular permeability confirmed in disease does not necessarily correlate with recognized histological changes in the glomerulus, suggesting that perhaps more subtle ultrastructural changes may be relevant. The epidemiology of microalbuminuria reveals a close association between systemic endothelial dysfunction and vascular disease, also implicating glomerular endothelial dysfunction in microalbuminuria. This review discusses the mechanisms of microalbuminuria in disease, particularly the emerging role of the glomerular endothelium and its glycocalyx, and examines its implications for cardiovascular disease in the pediatric population.

Orthostatic proteinuria and the spectrum of diurnal variability of urinary protein excretion in healthy children

The aim of this study was to characterize the 24-h and diurnal variability of urinary protein excretion and identify the prevalence of orthostatic proteinuria (OP) in healthy children. Upright, supine, and 24-h total urinary protein (UrTP) and creatinine clearance (CrCl) were measured in 91 healthy children ages 6-19 years. Urinary protein and creatinine excretions were calculated and examined by gender, age, Tanner stage, and body mass index (BMI). Orthostatic proteinuria (OP) was defined as a 24-h UrTP >100 mg/m(2) with a normal supine UrTP (<4 mg/m(2)/h). There exists a marked diurnal variability in UrTP. The upright UrTP rate was three to four-times greater than the supine rate. UrTP, adjusted for body surface area, is higher in boys than girls and increases with age and BMI. There is a similar increase in upright CrCl compared with supine. Urinary protein to creatinine ratio (UPcr) is strongly correlated with UrTP. OP is common, being found in 20% of children in this cohort, and is more common in boys and associated with age >10 years and BMI >85%. In children with OP, a first morning UPcr shows a value in the normal range, whereas a random daytime UPcr is elevated. There exists a diurnal variability in urinary protein excretion that is exaggerated in participants with OP. UPcr reliably estimates 24-h UrTP. Using current pediatric criteria, OP is very common, particularly in boys. A normal first morning UPcr ratio indicates that a child with elevated random urinary protein has OP.

Current issues in measurement and reporting of urinary albumin excretion

BACKGROUND

Urinary excretion of albumin indicates kidney damage and is recognized as a risk factor for progression of kidney disease and cardiovascular disease. The role of urinary albumin measurements has focused attention on the clinical need for accurate and clearly reported results. The National Kidney Disease Education Program and the IFCC convened a conference to assess the current state of preanalytical, analytical, and postanalytical issues affecting urine albumin measurements and to identify areas needing improvement.

CONTENT

The chemistry of albumin in urine is incompletely understood. Current guidelines recommend the use of the albumin/creatinine ratio (ACR) as a surrogate for the error-prone collection of timed urine samples. Although ACR results are affected by patient preparation and time of day of sample collection, neither is standardized. Considerable intermethod differences have been reported for both albumin and creatinine measurement, but trueness is unknown because there are no reference measurement procedures for albumin and no reference materials for either analyte in urine. The recommended reference intervals for the ACR do not take into account the large intergroup differences in creatinine excretion (e.g., related to differences in age, sex, and ethnicity) nor the continuous increase in risk related to albumin excretion.

DISCUSSION

Clinical needs have been identified for standardization of (a) urine collection methods, (b) urine albumin and creatinine measurements based on a complete reference system, (c) reporting of test results, and (d) reference intervals for the ACR.

Nutcracker syndrome in children with orthostatic proteinuria: diagnosis on the basis of Doppler sonography

OBJECTIVE

To evaluate the Doppler sonographic findings of the left renal vein in children with orthostatic proteinuria in comparison with healthy children and to propose more reliable sonographic criteria for diagnosing nutcracker syndrome in children.

METHODS

Doppler sonographic findings in 47 children with orthostatic proteinuria and in 27 healthy control subjects were compared. The diagnosis of orthostatic proteinuria was made on the basis of clinical and laboratory findings. The peak velocity and anteroposterior diameter were measured at the hilar and aortomesenteric portions of the left renal vein. The means +/- 2 SD of the anteroposterior diameter ratio and peak velocity ratio between the 2 portions were calculated for control subjects and used as the cutoff levels for nutcracker syndrome.

RESULTS

The peak velocity ratios between aortomesenteric and hilar portions were 5.21+/-2.55 in the patient group and 2.57+/-0.70 in the control group. The anteroposterior diameter ratios between the 2 portions were 5.31+/-2.65 in the patient group and 2.77+/-0.69 in the control group. We set the cutoff level of anteroposterior diameter and peak velocity ratios for the diagnosis of nutcracker syndrome at mean +/- 2 SD of the value for the control group (3.98 for the peak velocity ratio and 4.16 for the anteroposterior diameter ratio). When these cutoff levels were applied, the patients with orthostatic proteinuria had abnormal levels of anteroposterior diameter in 27 (57.4%) of 47, peak velocity in 30 (63.8%) of 47, and both in 23 (48.9%) of 47.

CONCLUSIONS

Nutcracker syndrome may be an important cause of orthostatic proteinuria in children. Doppler sonography of the left renal vein may be a useful screening tool in patients with suspected orthostatic proteinuria to evaluate whether the cause is nutcracker syndrome.

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.

Proteinuria as a risk factor for cardiovascular disease and mortality in older people: a prospective study

BACKGROUND

The prognostic significance of proteinuria in older people is not well defined. We examined the associations between proteinuria and incident coronary heart disease, cardiovascular mortality, and all-cause mortality in older people.

SUBJECTS AND METHODS

Casual dipstick proteinuria was determined in 1,045 men (mean [+/- SD] age 68 +/- 7 years) and 1,541 women (mean age 69 +/- 7 years) attending the 15th biennial examination of the Framingham Heart Study. Participants were divided by grade of proteinuria: none (85.3%), trace (10.2%), and greater-than-trace (4.5%). Cox proportional hazards analyses were used to determine the relations of baseline proteinuria to the specified outcomes, adjusting for other risk factors, including serum creatinine level.

RESULTS

During 17 years of follow-up, there were 455 coronary heart disease events, 412 cardiovascular disease deaths, and 1,214 deaths. In men, baseline proteinuria was associated with all-cause mortality (hazards ratio [HR] = 1.3, 95% confidence interval [CI] 1.0 to 1.7 for trace proteinuria; HR = 1.3, 95% CI 1.0 to 1.8 for greater-than-trace proteinuria; P for trend = 0.02). In women, trace proteinuria was associated with cardiovascular disease death (HR = 1. 6, 95% CI 1.1 to 2.4), and all-cause mortality (HR = 1.4, 95% CI 1.1 to 1.7).

CONCLUSION

Proteinuria is a significant, although relatively weak, risk factor for all-cause mortality in men and women, and for cardiovascular disease mortality in women.

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.

Evaluating the child with proteinuria

Proteinuria is a common laboratory finding in children. It might represent a benign condition or herald the presence of a serious underlying renal disease or systemic disorder. Investigation to confirm a diagnosis or seek reassurance is important. This paper discusses the various causes of proteinuria, and those aspects of the history, physical examination, and the laboratory tests that will help determine the cause or reassure that a serious problem is not currently present.

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.

Entrapment of left renal vein in children with orthostatic proteinuria

We found that patients with orthostatic protein-uria had entrapment of the left renal vein (LRV) by the aorta and superior mesenteric artery (SMA). Of 15 patients studied, ultrasonographic examination showed 13 cases of typical LRV entrapment with prestenotic dilatation, and 2 cases of mild LRV compression between the aorta and SMA. Intra-arterial digital subtraction angiography and monitoring of pull-back pressure from LRV to the inferior vena cava (IVC) were performed on 2 patients with 4+ proteinuria. Accumulation of contrast medium was seen with mild back-flow to the collateral veins, and pressure gradients between LRV and IVC were 4 mmHg and 8 mmHg, respectively. Eighty school-children formed a control group and were investigated ultrasonically. Nine showed typical LRV entrapment, among whom 3 had moderate to massive orthostatic proteinuria. The discovery of LRV entrapment in patients with orthostatic proteinuria gives definite evidence of LRV congestion and may be possibly a cause of massive protein secretion from the left kidney.

An office approach to hematuria and proteinuria

An organized practical approach for the pediatrician to use in evaluating a child with hematuria or proteinuria emphasizes common conditions and stepwise laboratory/radiologic investigations. Additional points of emphasis include when to refer to a pediatric nephrologist or urologist and when to consider renal biopsy. Real case statistics and salient examples from the major published studies should assist the pediatrician in counseling the patient and his or her family, especially when there is no medical indication to refer to a specialist.

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

We examined the effects of body position and exercise on the random urinary protein/creatinine ratio (Up/Ucr) in healthy adolescents, to provide reference data to be used in a simplified evaluation of proteinuria. Random urine samples were obtained during recumbency and after both ambulation and exercise in 116 subjects. The Up/Ucr was significantly (P less than 0.0001) higher with increasing levels of activity, and was widely variable, especially during the upright and postexercise periods. No sex-related differences in Up/Ucr were noted, except during recumbency, when values were significantly (P less than 0.001) higher in females. The urinary dipstick was found to be less sensitive as a tool to define abnormal degrees of recumbent proteinuria. We conclude that body position and exercise have significant effects on protein excretion, and suggest that the Up/Ucr in recumbent and upright urine samples will be useful in the evaluation of proteinuria.

Progression of orthostatic proteinuria to focal and segmental glomerulosclerosis

Focal glomerulosclerosis, with the nephrotic syndrome and progressive renal insufficiency, developed in a 15-year-old boy who presented initially 1 year earlier with orthostatic proteinuria. Although generally considered to be a benign disorder, this case suggests that on rare occasions, serious glomerular diseases may develop in patients with orthostatic proteinuria or that significant glomerular disease may occasionally present with postural proteinuria.

The prognostic significance of proteinuria: the Framingham study

Despite considerable clinical experience with proteinuria, its prognostic meaning in the ambulatory general population is poorly documented. From a 16-year study of 5209 men and women in the Framingham cohort it is evident that proteinuria, even in casual urine specimens, carries substantial risk with the mortality rate increased threefold. Proteinuria was three times as common in hypertensive persons and also occurred to excess in diabetic patients and in persons with cardiac enlargement. In the absence of these factors, proteinuria was so uncommon that its risk could not be accurately assessed. Among persons with these associated risk factors, those with proteinuria have higher death rates than those without proteinuria. In men, overall mortality and cardiovascular mortality rates remained significantly increased even when other contributors to risk were taken into account. Proteinuria in the ambulatory general population is not a benign condition and carries a serious prognosis. It appears to reflect widespread vascular damage.

Assessment of proteinuria using random urine samples

To determine the feasibility of accurately assessing proteinuria using random urine samples, 24-hour urine samples were obtained from five healthy adult volunteers and 15 children (ages 5 to 17 years) with renal disease. Protein concentration was measured using a Coomassie blue binding technique, and total protein excretion was compared with the urinary protein/creatinine ratio (Up/Ucr). Total protein excretion varied from 28.3 mg to 12.3 gm, or 15.4 to 8500 mg/m2/day, and Up/Ucr ranged from 27.9 to 7650 micrograms/mg in the 24-hour samples; the correlation was highly significant (r = 0.99; P less than 0.001). Reference values for urinary protein concentration and Up/Ucr were established by examining random urine samples in 219 healthy individuals (ages 1 month to 61 years). Age-related differences in protein concentration were noted, and 95th percentiles were calculated as the upper limit of normal. The results of our study indicate that Up/Ucr is an accurate assessment of quantitative protein excretion and could largely replace the collection of timed urine samples for the assessment of proteinuria.

Proteinuria in children. Review and evaluation

Current information relating to the clinical significance of proteinuria in children through adolescence was reviewed. Proteinuria may be transient, orthostatic, or fixed. The data indicate that only fixed proteinuria-that is, proteinuria on multiple urine examinations without postural exaggeration-may indicate serious glomerular disease. The patient should be followed with periodic but infrequent examinations, avoiding unnecessary, complicated, and hazardous investigations.