Body mass index modulates postural proteinuria

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.

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.

Value of micro-proteinuria in combination with ultrasonography of the left renal vein in the diagnosis of orthostatic proteinuria

Background

This study aimed to evaluate the clinical value of micro-proteinuria in combination with ultrasonography of the left renal vein (LRV) in the diagnosis of orthostatic proteinuria (OP).

Methods

The patients with suspected OP received West test, upright lordotic position test, Robinson test, ultrasonography of the LRV, and detection of morning urine micro-proteinuria and micro-proteinuria after activity. The sensitivity (Se), specificity (Sp), positive and negative predictive values (PPV and NPV), positive and negative likelihood ratios (PLR and NLR) and Youden's index (YI) for micro-proteinuria, ultrasonography of the LRV and both of them in the diagnosis of OP were analyzed.

Results

From January 2013 to January 2018, 75 patients (M/F: 38/37) were recruited. Sixty patients were diagnosed with OP (M/F: 29/31, median age at onset: 10.6±2.80 years); 15 patients had no OP (M/F: 9/6, median age at onset: 10.9±3.25 years); the LRV entrapment, urine Alb/Cr, IgG/Cr, and NAG/Cr after activity were significantly different between OP group and non-OP group (Z=-3.55, -4.10, -4.01, -3.04, P<0.05). The area under the curve (AUC) of urine Alb/Cr, IgG/Cr, NAG/Cr, and the ratio of anteroposterior (AP) for LRV in the hilar and narrow portions (a/b) was 0.84, 0.84, 0.76 and 0.58, respectively, and the best cut-off value was 13.2 mg/mmol, 2.52 mg/mmol, 0.64 U/mmol and 4.06, respectively. The combination of ultrasonography of the LRV and elevated micro-proteinuria after activity could achieve the Se, Sp, PPV, NPV, PLR (weighted by prevalence, W), NLR (W) and YI at 93.3% (95% CI: 0.83-0.98), 66.7% (95% CI: 0.39-0.87), 91.8% (95% CI: 0.81-0.97), 71.4% (95% CI: 0.42-0.90), 11.2 (95% CI: 4.82-26.00), 0.40 (95% CI: 0.17-0.97) and 60%, respectively, in the diagnosis of OP.

Conclusions

The micro-proteinuria in combination of ultrasonography of the LRV is helpful for the preliminary screening of OP in patients with suspected OP.

Individual and Environmental Factors Associated with Proteinuria in Korean Children: A Multilevel Analysis

Proteinuria is a significant sign of childhood renal disorders. However, little is known about how sociodemographic and environmental factors are related to the presence of proteinuria among children and adolescents. This paper focuses on the prevalence of proteinuria and its risk factors among children and adolescents. This study conducted a secondary analysis of data from the 2016 Sample Schools Raw Data of Health Examination for School Students (SSRDHESS). Data collected from 27,081 students who had undergone a health screening were analyzed using Chi-square tests, independent t-tests, and multilevel logistic regression analysis. The prevalence of proteinuria was higher in the thin group than in the normal weight group (adjusted odds ratio (aOR) = 1.77; 95% confidence interval (CI) = 1.34–2.33) and lower in the overweight/obese group (aOR = 0.64; 95% CI = 0.51–0.80). Additionally, those in metropolitan and small–medium sized cities had a proteinuria prevalence about 1.5-fold higher than that of those in rural areas (95% CI = 1.08–2.02, 95% CI = 1.19–1.92, respectively). Proteinuria was associated with environmental pollution, including smoking rate, ambient particulate matter and heavy metals in drinking water (aOR = 1.10; 95% CI = 1.01–1.20; aOR = 1.06; 95% CI = 1.01–1.11, aOR = 1.001; 95% CI = 1.0001–1.0015). These results suggest that to improve health management effectiveness, kidney disease prevention efforts for children and adolescents should focus on geographical area and environmental pollution, as well as body weight as individual factors.

Micro- and macroscopic hematuria caused by renal vein entrapment: systematic review of the literature

BACKGROUND

Hematuria secondary to renal vein entrapment is mentioned only passing in textbooks and reviews.

METHODS

We performed a search of the National Library of Medicine database for peer-reviewed publications using the terms "renal vein" or "nutcracker" and "hematuria".

RESULTS

We identified 187 published reports/studies that covered 736 patients, of whom 288 had microscopic hematuria and 448 had macroscopic hematuria. The patient cohort comprised 159 patients aged ≤17 years. Abdominal pain was absent in  approximately 65% of all patients, and a clinically relevant left-sided varicocele was observed in 29% of the male patients. A normal pre-aortic left renal vein and an anomalous anatomy were noted in 680 and 56 patients, respectively. The body mass index (BMI) was lower in patients with renal vein entrapment than in the controls, with a regression of hematuria correlating with an increase in BMI. A surgical procedure was attempted in 34% of the patients, of which the most common were endovascular stenting and transposition of the renal vein distally into the vena cava.

CONCLUSIONS

In cases of unexplained hematuria with or without abdominal pain, clinicians should consider the diagnosis of renal vein congestion, especially in males with varicocele. Ultrasonic Doppler flow scanning is the recommended initial diagnostic modality in these patients. Expectation management is advised in the great majority of cases.

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.

U-shaped association between body mass index and proteinuria in a large Japanese general population sample

BACKGROUND

There is little data on the association between body mass index (BMI) and proteinuria.

METHODS

This was a cross-sectional cohort study assessing the association between BMI and proteinuria in a large Japanese population. Using a nationwide health check-up database of 212,251 Japanese aged >20 years with no pre-existing cardiovascular diseases (185,183 men, median age 66 years; 127,068 women, median age 65 years), we examined the association between BMI and proteinuria (≥ 1+ on dipstick).

RESULTS

Subjects were divided into 11 subgroups by BMI grading in 1 kg/m(2) intervals from 18.5-27.5 kg/m(2). A BMI of approximately 22 ± 0.5 kg/m(2) was considered optimal for Japanese; therefore, this subgroup was set as a reference when logistic analysis was applied. Age, waist circumference, height, weight, smoking and drinking habits, use of medications such as antihypertensive, antidiabetic, or antihyperlipidemic, as well as proteinuria, estimated glomerular filtration rate (eGFR), chemistry data, and blood pressure levels were significantly different between subgroups in both genders. The odds ratio for proteinuria showed a U-shape in men and women, even after adjustment for significant covariates such as age, waist circumference, systolic blood pressure, eGFR, fasting plasma glucose, triglyceride, low-density lipoprotein, antihypertensive use, antidiabetic use, antihyperlipidemic use, and lifestyle factors (smoking and drinking). Gender differences were also prominent--a BMI <20.4 kg/m(2) was significantly associated with proteinuria in men compared to a BMI <18.4 kg/m(2) in women. On the other hand, a BMI ≥ 25.5 kg/m(2) was also significantly associated with proteinuria in men compared to a BMI ≥ 22.5 kg/m(2) in women.

CONCLUSIONS

We found that BMI levels were associated with proteinuria in a U-shaped manner and showed marked gender differences. Health guidance should not only focus on higher BMI subjects, but also on thin subjects, in terms of the prevention of chronic kidney disease.

Renal vein obstruction and orthostatic proteinuria: a review

OBJECTIVES

The cause of orthostatic proteinuria is not clear but may often relate to obstruction of the left renal vein in the fork between the aorta and the superior mesenteric artery (=renal nutcracker). However, reports dealing with proteinuria only marginally refer to this possible cause of orthostatic proteinuria. We analysed the corresponding literature.

RESULTS

Five reports addressed the frequency of renal nutcracker in 229 subjects with orthostatic proteinuria. Their age ranged between 5.2 and 17 years (female-to-male ratio: 0.96:1.00). Imaging studies demonstrated renal nutcracker in 156 (68%) subjects. Renal nutcracker was also demonstrated in 9 anecdotal reports for a total of 53 subjects with postural proteinuria. Very recently, 13 Italian subjects with orthostatic proteinuria associated with renal nutcracker were reassessed 6 years after the initial diagnosis: in nine subjects, both orthostatic proteinuria and renal nutcracker had disappeared; in three, both orthostatic proteinuria and renal nutcracker had persisted; and in one, orthostatic proteinuria had persisted unassociated with renal nutcracker.

CONCLUSIONS

These data provide substantial support for renal nutcracker as a common cause of orthostatic proteinuria.