Urinary albumin excretion: a predictor of glomerular findings in adults with microscopic haematuria

How to define and assess the clinically significant causes of hematuria in childhood

Given the wide diversity of causes of hematuria, ranging from simple urinary tract infections with rapid recovery to severe glomerulonephritis with fast decline in kidney function, it is essential to recognize the underlying disease. The first objective of the assessment is to determine whether the cause of the hematuria is medically significant. The combination of hematuria with proteinuria, the presence of hypertension, or worsening kidney function can represent signs of progressive kidney disease. Differentiating the various causes of hematuria is often simple and obvious based on the clinical signs and gross appearance of the urine. However, in some instances, additional non-invasive investigations, such as ultrasound imaging, urinary red cell morphology, measurement of calcium and other solutes in the urine, evaluation of kidney function, and protein excretion, are needed to elucidate the nature of the hematuria. Taking a detailed family history can help in establishing the underlying cause in cases of familial hematuria. On the other hand, the decision to perform a kidney biopsy in children with asymptomatic hematuria remains a challenging issue for clinicians. Ultimately, the frequency of diagnosis of glomerular involvement causing hematuria may depend on the threshold for performing a kidney biopsy. The following review will focus on the diagnostics of hematuria, starting with difficulties regarding its definition, followed by various means to differentiate between urinary, glomerular, and other causes, and finally reviewing the most common diseases that, due to their frequency or their effect on kidney function, present a diagnostic challenge in everyday practice.

Monitoring Immune Responses in IgA Nephropathy: Biomarkers to Guide Management

IgA nephropathy (IgAN) is the commonest biopsy-reported primary glomerulonephritis worldwide. It has an incidence which peaks among young adults, and 30 to 40% of patients' progress to end stage kidney disease within twenty years of diagnosis. Ten-year kidney survival rates have been reported to be as low as 35% in some parts of the world. The successful management of IgAN is limited by an incomplete understanding of the pathophysiology of IgAN and a poor understanding of how pathophysiology may vary both from patient to patient and between patient groups, particularly across races. This is compounded by a lack of rigorously designed and delivered clinical trials in IgAN. This is slowly changing, with a number of Phase 2 and 3 clinical trials of novel therapies targeting a number of different putative pathogenic pathways in IgAN due to report in the next 5 years. From our current, albeit limited, understanding of the pathophysiology of IgAN it is unlikely a single therapy will be effective in all patients with IgAN. The successful management of IgAN in the future is, therefore, likely to be reliant on targeted therapies, carefully selected based on an individualized understanding of a patient's risk of progression and underlying pathophysiology. The potential role of biomarkers to facilitate personalization of prognostication and treatment of IgAN is immense. Here we review the progress made over the past decade in identifying and validating new biomarkers, with a particular focus on those that reflect immunological responses in IgAN.

The Application of SILAC Mouse in Human Body Fluid Proteomics Analysis Reveals Protein Patterns Associated with IgA Nephropathy

Body fluid proteome is the most informative proteome from a medical viewpoint. But the lack of accurate quantitation method for complicated body fluid limited its application in disease research and biomarker discovery. To address this problem, we introduced a novel strategy, in which SILAC-labeled mouse serum was used as internal standard for human serum and urine proteome analysis. The SILAC-labeled mouse serum was mixed with human serum and urine, and multidimensional separation coupled with tandem mass spectrometry (IEF-LC-MS/MS) analysis was performed. The shared peptides between two species were quantified by their SILAC pairs, and the human-only peptides were quantified by mouse peptides with coelution. The comparison for the results from two replicate experiments indicated the high repeatability of our strategy. Then the urine from Immunoglobulin A nephropathy patients treated and untreated was compared by this quantitation strategy. Fifty-three peptides were found to be significantly changed between two groups, including both known diagnostic markers for IgAN and novel candidates, such as Complement C3, Albumin, VDBP, ApoA,1 and IGFBP7. In conclusion, we have developed a practical and accurate quantitation strategy for comparison of complicated human body fluid proteome. The results from such strategy could provide potential disease-related biomarkers for evaluation of treatment.

Asymptomatic microscopic haematuria in young males

AIM

The study involved 120 young males (aged 20.5 +/- 2.5 years) having undergone successful kidney biopsy because of asymptomatic haematuria with the aims to assess the prevalence of histological diagnosis and the natural history of the disease.

METHODS

The patients were selected from the population of conscripts who were referred to our clinic as a result of asymptomatic microhaematuria. All patients had a negative history of kidney disease, normal creatinine clearance (Ccr), while extrarenal causes of microhaematuria were excluded. The patients were divided into a group of 62 patients with isolated microhaematuria (IMH; proteinuria < 0.3 g/day) and a group of 58 patients with asymptomatic microhaematuria and proteinuria (AMHP; proteinuria > 0.3 g/day). After kidney biopsy patients were monitored for 3-9 years.

RESULTS

Normal biopsies and minor abnormalities were more frequent in IMH than in AMHP patients, who had IgA nephritis more frequently and significantly higher total pathohistological score. Based on the clinical and histological features, recommendations on patients' ability for military service were made. During the follow-up period, normal Ccr maintained in all patients. Macrohaematuria appeared in 42 patients and proteinuria worsened in eight patients (seven with AMHP). Urinary abnormalities disappeared in 20 patients with IMH and in eight with AMHP (p = 0.04).

CONCLUSION

Minimal histological changes and disappearance of urinary abnormalities were more frequent in IMH than in AMHP patients. Kidney biopsy is useful only in patients with AMHP but it is not necessary in IMH patients.

Proteinuria after kidney transplantation, relationship to allograft histology and survival

Proteinuria is associated with reduced kidney allograft survival. Herein we assessed the association between proteinuria, graft histology and survival. The cohort included 613 kidney allograft recipients who had proteinuria (measured) and surveillance biopsies at 1-year posttransplant. Proteinuria >150 mg/day was detected in 276 patients (45%) and in 182 of these, proteinuria was below 500. In >84% of patients even low levels of proteinuria were associated with albuminuria. Proteinuria was associated with the presence of graft glomerular pathology and the use of sirolimus. Eighty percent of patients with proteinuria >1500 mg/day had glomerular pathology on biopsy. However, lower levels of proteinuria were not associated with specific pathologies at 1 year. Compared to no sirolimus, sirolimus use was associated with higher prevalence of proteinuria (40% vs. 76%, p < 0.0001) and higher protein excretion (378 + 997 vs. 955 + 1986 mg/day, p < 0.0001). Proteinuria was associated with reduced graft survival (HR = 1.40, p = 0.001) independent of other risk factors including, glomerular pathology, graft function, recipient age and acute rejection. The predominant pathology in lost allografts (n = 57) was glomerular, particularly in patients with 1-year proteinuria >500. Thus, proteinuria, usually at low levels (<500 mg/day), is present in 45% of recipients at 1 year. However, and even low levels of proteinuria relate to poor graft survival. Proteinuria and glomerular pathology relate independently to survival.

Mesangial proliferative glomerulonephritis with aldosterone-producing adenoma

We describe a case of mesangial proliferative glomerulonephritis (MesPGN), the clinical symptoms of which were exacerbated by aldosterone-producing adenoma (APA). A 45-year-old man, who had had a history of hypertension for several years, presented with renal derangement, with serum creatinine at its upper normal limit and with microhematuria and proteinuria. He also presented with hypokalemia, with a plasma aldosterone concentration at its upper normal limit and plasma renin activity at its lower normal limit. After the administration of spironolactone, we resected his left adrenal gland, which had a nodular lesion as well as aldosterone hypersecretion. The treatment normalized his arterial blood pressure and serum potassium concentration. Although his proteinuria disappeared with the reduction in arterial blood pressure, the microhematuria continued. The administration of losartan because of the histological finding of MesPGN reduced the amount of hematuria. A dissociated response of hematuria and proteinuria to antihypertensive treatment indicated that MesPGN was coincidental with APA.

Natural History and Prognostic Factors of IgA Nephropathy Presented with Isolated Microscopic Hematuria in Chinese Patients

BACKGROUND/AIMS

IgA nephropathy (IgAN) with isolated microscopic hematuria (IMH) is prevalent in Asian countries including China. However, the natural history of IgAN with IMH has not yet been clarified. The aim of this study was to review the natural course and prognostic factors of IgAN with IMH in Chinese patients.

METHODS

We retrospectively studied 135 patients (43 males and 92 females) followed up for a mean period of 92 +/- 28 months. In order to identify factors associated with renal progression, clinical and pathological data at onset were reviewed.

RESULTS

During the follow-up period, hematuria of 16 patients (12%) disappeared while persistent microscopic hematuria was seen in 119 patients (88%), and proteinuria was present in 39 patients (29%). The prevalence of hypertension was 32% (43 patients), and 20% (27 patients) developed renal insufficiency. The prevalence of proteinuria and hypertension in the microalbuminuria group was significantly higher than those in the normoalbuminuria group. Poor renal outcome is usually associated with hematuria, microalbuminuria, and tubulointerstitial lesions.

CONCLUSION

IgAN with IMH may not imply favorable outcome, so early diagnosis and careful follow-up are clinically significant. Hematuria, microalbuminuria, and tubulointerstitial lesions are useful markers to identify those patients at high risk for renal progression.

Useful indicators for performing renal biopsy in adult patients with isolated microscopic haematuria

Among adult patients with isolated microscopic haematuria (IMH) which is defined as persistent microscopic haematuria but without proteinura, hypertension, renal insufficiency, urinary tract infection or structural abnormality of the urinary tract, some patients have chronic glomerulonephritis (CGN), in whom early diagnosis by renal biopsy is beneficial to timely intervention. Nevertheless, a considerable number of patients with optimistic prognosis [e.g. thin basement membrane nephropathy (TBMN)] undergo invasive and needless renal biopsy. Indicators for weighing the necessity of renal biopsy would be clinically significant. To investigate the value of urinary albumin/creatinine ratio (UACR), serum IgA level, serum C3 level and serum IgA to C3 ratio in predicting the necessity of renal biopsy for adult patients with IMH, 216 patients were studied retrospectively. Patients were divided into: (CGN group, n=137), (TBMN group, n=56) and normal biopsy (normal group, n=23). Of all patients, 131 (61%) evidenced microalbuminuria (UACR=30-299 mg/g) and 85 (39%) had normoalbuminuria (UACR<30 mg/g). The mean value of UACR in CGN group was higher (96+/-17 mg/g) compared with that in TBMN (20+/-4 mg/g, p<0.01) or normal (18+/-3 mg/g, p<0.01) group. The mean values of serum IgA and serum IgA/C3 ratio in patients with IgA nephropathy (IgAN) were significantly higher than those with non-IgAN (380+/-103:217+/-99 mg/dl, p<0.01; 4.5+/-1.2 : 2.4+/-0.9, p<0.01). The odds ratio for distinguishing IgAN from non-IgAN was significantly correlated with serum IgA level and serum IgA to C3 ratio. For adult patients with IMH, UACR, serum IgA level and serum IgA to C3 ratio are non-invasive markers for predicting the necessity of renal biopsy.

Cis and trans regulatory elements in NPHS2 promoter: implications in proteinuria and progression of renal diseases

Podocin (NPHS2) expression in podocytes is associated with variable degrees of proteinuria and progression to renal failure in different glomerular diseases that suggests different expression profiles in NPHS2 promoter. Three functional polymorphisms in NPHS2 promoter (-51T, -116T, and -535 insCTTTTTT(3)) were found determining strong downregulation (-73, -59, and -82%, respectively) of the reporter gene expression when transfected in podocytes. Electrophoretic mobility shift assay experiments showed that all wild-type variants (-51G, -116C, and -535 insCTTTTTT(2)) formed specific DNA-protein complexes with podocyte nuclear extracts that were abolished by the presence of the rare forms (-51T, -116T, and -535 insCTTTTTT(3)). In the case of -51G, upstream stimulatory factor-1 (USF1) was identified as the specific trans element in accord to binding inhibition experiments and USF1 RNAi silencing. Haplotype analysis of 204 normal controls and 545 patients with renal diseases (308 immunoglobulin (Ig)A nephropathy and 237 focal segmental glomerulosclerosis) evidenced that -116/-51 and -535/P2OL formed two blocks in strong linkage disequilibrium in both normal and pathological cohorts. The high NPHS2 promoter profile -116C/-51G haplotype was more frequent in patients with IgA nephropathy (P-value=0.005) and was associated with a better clinical outcome in terms of proteinuria and creatinine levels. Overall our study describes functional variants of NPHS2 promoter and characterizes trans-acting elements that modulate podocin expression in the kidney. High producer NPHS2 promoter haplotypes seem protective in patients with chronic glomerular diseases.

Urinary liver-type fatty acid-binding protein: discrimination between IgA nephropathy and thin basement membrane nephropathy

BACKGROUND

Microscopic hematuria without proteinuria is a common clinical finding in cases of immunoglobulin A (IgA) nephropathy and of thin basement membrane nephropathy. Liver-type fatty acid-binding protein (L-FABP) is expressed in renal proximal tubules and is reported to be a useful marker of the progression of chronic glomerulonephritis.

AIM

To assess urinary L-FABP levels for differential diagnosis in patients with microscopic hematuria but without proteinuria.

METHODS

This was a multi-center retrospective study. Thirty adult patients who underwent renal biopsy for microscopic hematuria and 20 healthy adult volunteers were included in this study. Urinary L-FABP levels were measured by enzyme-linked immunosorbent assay and compared, particularly between those diagnosed with IgA nephropathy and those diagnosed with thin basement membrane nephropathy.

RESULTS

Twelve (40%) patients had IgA nephropathy, 6 (20%) had thin basement membrane nephropathy and 12 (40%) had normal biopsy findings. The urinary L-FABP level was significantly higher in patients with IgA nephropathy (38.4 +/- 26.8 microg/g Cr) than in healthy subjects (5.8 +/- 4.0 microg/g Cr) (p < 0.01); however, the level in patients with thin basement membrane nephropathy or normal biopsy results was comparable to that in healthy subjects. Follow-up data were available for 11 of the 12 patients with IgA nephropathy who initially had no proteinuria. After 24 months, 4 of the 11 were found to have proteinuria, and the urinary L-FABP level had increased from 40.6 +/- 30.5 microg/g Cr to 58.8 +/- 40.5 microg/g Cr (p < 0.01).

CONCLUSIONS

Our data suggest that the urinary L-FABP level can be used to discriminate between IgA nephropathy and thin basement membrane nephropathy in patients with microscopic hematuria.

Value of urinary excretion of microalbumin in predicting glomerular lesions in children with isolated microscopic hematuria

Urinary microalbumin excretion was assessed in 76 children with asymptomatic microscopic hematuria in whom the presence of proteinuria, hypertension, reduced renal function, hypercalciuria, urinary tract infection or structural abnormality of the urinary tract had been excluded. All children underwent a percutaneous kidney biopsy to determine whether microalbumin excretion can be used as a marker to predict the source of hematuria. Microalbumin excretion was considered normal if the urinary ratio of microalbumin to creatinine (MA/Cr ug/mg) was < or =30. Twenty-two (29%) had microalbuminuria (MA/Cr 96+/-30 microg/mg) and 54 (71%) had normal albumin excretion (MA/Cr 13+/-2 microg/mg). Of those with normoalbuminuria, 38 (70%) had normal renal tissue, 15 (28%) thin glomerular basement membrane (TGBM) disease and 1 (2%) IgA nephropathy. In contrast, 20 (91%) of those with microalbuminuria had IgA nephropathy and 2 (9%) had TGBM disease. The mean urinary MA/Cr ratio for all IgA children was 89+/-32 microg/mg higher compared with a value for the children with TGBM disease (14 +/-3 microg/mg, P <0.001) or children whose renal biopsy appeared normal (11+/-2 microg/mg, P <0.001). Statistical analysis revealed no significant differences between the mean MA/Cr ug/mg ratio for children with TGBM disease and those with normal glomerular findings. Fourteen of the 20 children with IgA nephropathy who also had microalbuminuria were treated with an angiotensin-converting enzyme (ACE) inhibitor. Over a mean follow-up of 51 months, none developed overt proteinuia; hematuria resolved and microalbuminuria returned to normal in eight (57%) during therapy with the ACE-inhibitor. In contrast, hematuria persisted and prtoteinuria developed in the other untreated children. None of the children with TGBM disease developed overt proteinuria after a mean of 51 months. Hematuria was persistent in children with TGBM disease, but often resolved in those whose biopsies were completely normal. These data suggest that determination of urinary microalbumin excretion is warranted in the routine examination of children with isolated microscopic hematuria. Routine screening for microalbuminuria may help to identify a subgroup of patients with IgA nephropathy who are at high risk for progressive kidney disease and need more intensive therapy and closer follow-up.