Glomerular hypertrophy in minimal change disease predicts subsequent progression to focal glomerular sclerosis

Nephrotic Syndrome Throughout Childhood: Diagnosing Podocytopathies From the Womb to the Dorm

The etiologies of podocyte dysfunction that lead to pediatric nephrotic syndrome (NS) are vast and vary with age at presentation. The discovery of numerous novel genetic podocytopathies and the evolution of diagnostic technologies has transformed the investigation of steroid-resistant NS while simultaneously promoting the replacement of traditional morphology-based disease classifications with a mechanistic approach. Podocytopathies associated with primary and secondary steroid-resistant NS manifest as diffuse mesangial sclerosis, minimal change disease, focal segmental glomerulosclerosis, and collapsing glomerulopathy. Molecular testing, once an ancillary option, has become a vital component of the clinical investigation and when paired with kidney biopsy findings, provides data that can optimize treatment and prognosis. This review focuses on the causes including selected monogenic defects, clinical phenotypes, histopathologic findings, and age-appropriate differential diagnoses of nephrotic syndrome in the pediatric population with an emphasis on podocytopathies.

Glomerular hyperfiltration and hypertrophy: an evaluation of maximum values in pathological indicators to discriminate "diseased" from "normal"

The success of sodium-glucose cotransporter 2 inhibitors and bariatric surgery in patients with chronic kidney disease has highlighted the importance of glomerular hyperfiltration and hypertrophy in the progression of kidney disease. Sustained glomerular hyperfiltration and hypertrophy can lead to glomerular injury and progressive kidney damage. This article explores the relationship between obesity and chronic kidney disease, focusing on the roles of glomerular hyperfiltration and hypertrophy as hallmarks of obesity-related kidney disease. The pathological mechanisms underlying this association include adipose tissue inflammation, dyslipidemia, insulin resistance, chronic systemic inflammation, oxidative stress, and overactivation of the sympathetic nervous system, as well as the renin-angiotensin aldosterone system. This article explains how glomerular hyperfiltration results from increased renal blood flow and intraglomerular hypertension, inducing mechanical stress on the filtration barrier and post-filtration structures. Injured glomeruli increase in size before sclerosing and collapsing. Therefore, using extreme values, such as the maximal glomerular diameter, could improve the understanding of the data distribution and allow for better kidney failure predictions. This review provides important insights into the mechanisms underlying glomerular hyperfiltration and hypertrophy and highlights the need for further research using glomerular size, including maximum glomerular profile, calculated using needle biopsy specimens.

Efficacy of low-dose rituximab in minimal change disease and prevention of relapse

BACKGROUND

Minimal change disease (MCD) is a major cause of nephrotic syndrome (NS) in children and a minority of adults. The higher tendency to relapse put patients at risk for prolonged exposure to steroids and other immunosuppressive agents. B cell depletion with rituximab (RTX) may be beneficial to the treatment and prevention of frequently relapsing MCD. Therefore, this study aimed to verify the therapeutic/preventive effects of low-dose RTX on the relapse in adult with MCD.

METHODS

A total of 33 adult patients were selected for the study, including 22 patients with relapsing MCD in relapse treatment group who were treated with low-dose RTX (200 mg per week × 4 following by 200 mg every 6 months) and 11 patients in relapse prevention group with complete remission (CR) after steroid therapy were treated with RTX (200 mg ×1 every 6 months) for preventing the relapse of MCD.

RESULTS

Of the 22 patients with MCD in relapse treatment group, there were 21 cases (95.45%) of remission [2 (9.09%) partial remission (PR), 19 (86.36%) CR], 1 (4.56%) no remission (NR) and 20 (90.90%) relapse-free. The Median duration of sustained remission was 16.3 months (3, 23.5 months, inter quartile range (IQR)). 11 patients in the relapse prevention group during a follow-up of 12 months (9-31 months) had no relapse. The average dose of prednisone in two groups after RTX treatment was significantly lower than before treatment.

CONCLUSION

The results of this study suggested low-dose RTX can significantly reduce relapse rate and steroid dose in adults with MCD with fewer side effects. Low-dose RTX regimens may be beneficial for the treatment of relapsing MCD in adults and may be the preferred regimen for patients at high risk for the development of adverse events from corticosteroids.

Demographic, clinical and laboratory characteristics of adult-onset minimal change disease in Turkey: Turkish Society of Nephrology-Glomerular Diseases (TSN-GOLD) Working Group

PURPOSE

In our study, diagnostic and demographic characteristics of patients diagnosed with minimal change disease (MCD) by biopsy, clinical and laboratory findings in our country were investigated.

METHODS

Data were obtained from the Turkish Society of Nephrology Glomerular Diseases (TSN-GOLD) Working Group database. Demographic characteristics, indications for biopsy, diagnosis of the glomerular diseases, comorbidities, laboratory and biopsy findings of all patients were recorded. The data presented are cross-sectional and includes application data for the biopsy period.

RESULTS

Of 3875 patients, 233 patients with MCD (median age 35.0 years) were included in the study, which constitutes 6.0% of the total glomerulonephritis database. Renal biopsy was performed in 196 (84.1%) patients due to nephrotic syndrome. Median serum creatinine was 0.7 (0.6-1.0) mg/dl, mean eGFR was 104 ± 33 ml/min/1.73 m² and median proteinuria 6000 mg/day. The number of patients under the age of 40 years was 139 (59.7%) (Group A), and the number of patients aged 40 years and over was 94 (40.3%) (Group B). Compared to Group A, global sclerotic glomeruli (24 vs. 43, p < 0.001) interstitial inflammation (15 vs. 34, p < 0.001), interstitial fibrosis (20 vs. 31, p = 0.001, vascular changes (10 vs. 25, p < 0.001) and tubular atrophy (18 vs. 30, p < 0.001) were found to be significantly higher in Group B. There was no difference in immunofluorescent staining properties between the two groups.

CONCLUSION

Our data are generally compatible with the literature. Chronic histopathological changes were more common in patients aged 40 years and older than younger patients. Studies investigating the effects of these different features on renal survival are needed.

Next-Generation Morphometry for pathomics-data mining in histopathology

Pathology diagnostics relies on the assessment of morphology by trained experts, which remains subjective and qualitative. Here we developed a framework for large-scale histomorphometry (FLASH) performing deep learning-based semantic segmentation and subsequent large-scale extraction of interpretable, quantitative, morphometric features in non-tumour kidney histology. We use two internal and three external, multi-centre cohorts to analyse over 1000 kidney biopsies and nephrectomies. By associating morphometric features with clinical parameters, we confirm previous concepts and reveal unexpected relations. We show that the extracted features are independent predictors of long-term clinical outcomes in IgA-nephropathy. We introduce single-structure morphometric analysis by applying techniques from single-cell transcriptomics, identifying distinct glomerular populations and morphometric phenotypes along a trajectory of disease progression. Our study provides a concept for Next-generation Morphometry (NGM), enabling comprehensive quantitative pathology data mining, i.e., pathomics.

The Pathology Lesion Patterns of Podocytopathies: How and why?

Podocytopathies are a group of proteinuric glomerular disorders driven by primary podocyte injury that are associated with a set of lesion patterns observed on kidney biopsy, i.e., minimal changes, focal segmental glomerulosclerosis, diffuse mesangial sclerosis and collapsing glomerulopathy. These unspecific lesion patterns have long been considered as independent disease entities. By contrast, recent evidence from genetics and experimental studies demonstrated that they represent signs of repeated injury and repair attempts. These ongoing processes depend on the type, length, and severity of podocyte injury, as well as on the ability of parietal epithelial cells to drive repair. In this review, we discuss the main pathology patterns of podocytopathies with a focus on the cellular and molecular response of podocytes and parietal epithelial cells.

Low regulatory T-cells: A distinct immunological subgroup in minimal change nephrotic syndrome with early relapse following rituximab therapy

Rituximab is an important second line therapy in difficult nephrotic syndrome (NS), especially given toxicity of long-term glucocorticoid or calcineurin inhibitor (CNI) use. However, clinical response to rituximab is heterogenous. We hypothesized that this was underpinned by immunological differences amongst patients with NS. We recruited a cohort of 18 subjects with glucocorticoid-dependent or glucocorticoid-resistant childhood-onset minimal change NS who received rituximab either due to CNI nephrotoxicity, or due to persistent glucocorticoid toxicity with inadequate response to cyclophosphamide or CNIs. Immunological subsets, T-cell activation assays and plasma cytokines were measured at baseline and 6-months post-rituximab. Time to relapse was bifurcated: 56% relapsed within one year ("early relapse"), while the other 44% entered remission mainly lasting ≥3 years ("sustained remission"). At baseline, early relapse compared to sustained remission group had lower regulatory T-cells (Tregs) [2.94 (2.25, 3.33)% vs 6.48 (5.08, 7.24)%, P<0.001], PMA-stimulated IL-2 [0.03 (0, 1.85)% vs 4.78 (0.90, 9.18)%, P=0.014] and IFNγ [2.22 (0.18, 6.89)% vs 9.47 (2.72, 17.0)%, P=0.035] levels. Lower baseline Treg strongly predicted early relapse (ROC-AUC 0.99, 95% CI 0.97-1.00, P<0.001). There were no differences in baseline plasma cytokine levels. Following rituximab, there was significant downregulation of Th2 cytokines in sustained remission group (P=0.038). In particular, IL-13 showed a significant decrease in sustained remission group [-0.56 (-0.64, -0.35)pg/ml, P=0.007)], but not in the early relapse group. In conclusion, early relapse following rituximab is associated with baseline reductions in Treg and T-cell hyporesponsiveness, which suggest chronic T-cell activation and may be useful predictive biomarkers. Sustained remission, on the other hand, is associated with downregulation of Th2 cytokines following rituximab.

Assessment of nephron number and single-nephron glomerular filtration rate in a clinical setting

Total nephron counts vary widely between individuals and may affect susceptibility to certain diseases, including hypertension and chronic kidney disease. Detailed analyses of whole kidneys collected from autopsy patients remain the only method for accurately counting nephrons in humans, with no equivalent option in living subjects. Current technological advances have enabled estimations of nephron numbers in vivo, particularly the use of total nephron number and whole-kidney glomerular filtration rate to estimate the mean single-nephron glomerular filtration rate. The use of this method would allow physicians to detect dynamic changes in filtration function at the single-nephron level rather than to simply count the number of nephrons that appear to be functioning. Currently available methods for estimating total nephron number in clinical practice have the potential to overcome limitations associated with autopsy analyses and may therefore pave the way for new therapeutic interventions and improved clinical outcomes.

Utility of glomerular morphometry in diagnosing pediatric renal disease

BACKGROUND

Morphometry has now become a useful adjunct to the diagnostic armamentarium of light, immunofluorescence, and electron microscopy, as it provides a deep insight into quantitative parameters of nephropathies. There has been a limited study on its utility especially in diagnosing pediatric renal diseases. This study is probably the first in India to assess the contribution of this diagnostic modality in pediatric renal disease to the best of authors' knowledge.

METHODS

It's a retrospective cross-sectional study covering a period of 05 years at a tertiary care hospital. The study includes 28 cases of pediatric (age till 14 years) nephropathies. The diseases were divided into two groups-nephrotic presentation and nephritic presentation. Glomerular morphometry was performed and mean was calculated for Bowman's capsule area, glomerular capillary tuft area, and Bowman's space area; for the three groups, respectively. Renal parameters serum creatinine, blood urea, 24 h urine protein were studied along with hemoglobin and serum cholesterol for the cases. Data were analyzed using SPSS software, version 25, for one-way ANOVA comparing mean in the three groups.

RESULTS

We found a positive and significant correlation between Bowman's capsule area with proteinuria, blood urea, and serum creatinine. There was positive and significant correlation between glomerular capillary tuft area and serum creatinine and Bowman's space area and proteinuria in both the groups.

CONCLUSION

Glomerular morphometry may contribute to the diagnosis of some glomerulopathies and the association between glomerular morphometric parameters and laboratory data may promote better understanding of the prognosis of these patients.

Time series changes in pseudo-R2 values regarding maximum glomerular diameter and the Oxford MEST-C score in patients with IgA nephropathy: A long-term follow-up study

There is no effectual pathological factor to predict the long-term renal prognosis of IgA nephropathy. Glomerular hypertrophy plays a crucial role in kidney disease outcomes in both experimental models and humans. This study aimed to 1) confirm the long-term prognostic significance of a maximal glomerular diameter (Max GD) ≥ 242.3 μm, 2) test a renal prognosis prediction model adding Max GD ≥ 242.3 μm to the Oxford classification (MEST-C), and 3) examine the time series changes in the long-term renal prognosis of patients with IgA nephropathy. The study included 43 patients diagnosed with IgA nephropathy from 1993 to 1998 at Kameda General Hospital. Renal prognosis with the endpoint of a 50% reduction in estimated glomerular filtration rate (eGFR) or the development of end-stage renal disease requiring dialysis was examined using logistic regression analysis, Cox regression analysis, and the Kaplan-Meier method. Pathological evaluation was performed using MEST-C and Max GD, and the validity of the prediction model was evaluated. Patients with Max GD ≥ 242.3 μm had significantly poor renal prognosis with multivariate Cox analysis (P = 0.0293). The results of the Kaplan-Meier analysis showed that kidney survival rates in the high-Max GD group were significantly lower than those in the low-Max GD group (log rank, P = 0.0043), which was confirmed in propensity score-matched models (log rank, P = 0.0426). Adding Max GD ≥ 242.3 μm to MEST-C improved diagnostic power of the renal prognosis prediction model by renal pathology tissue examination (R²: 3.3 to 14.5%, AICc: 71.8 to 68.0, C statistic: 0.657 to 0.772). We confirm that glomerular hypertrophy is useful as a long-term renal prognostic factor.

Maximum Glomerular Diameter and Oxford MEST-C Score in IgA Nephropathy: The Significance of Time-Series Changes in Pseudo-R2 Values in Relation to Renal Outcomes

The progression of immunoglobulin A nephropathy (IgAN) is currently assessed using the Oxford MEST-C score, which uses five indicators (mesangial and endocapillary hypercellularity, segmental sclerosis, interstitial fibrosis/tubular atrophy, and the presence of crescents) but has not yet included any risk factors related to glomerular size. Therefore, we tested whether adding another indicator, maximal glomerular diameter (Max GD), would improve the prognostic ability of this scoring system. The data of 101 adult patients diagnosed with IgAN between March 2002 and September 2004 were reviewed. We used McFadden’s pseudo-R² and the corrected Akaike information criterion to assess model fit and the concordance (C)-statistic to assess discriminatory ability. A 10 μm increase in Max GD was significantly associated with a composite outcome (≥50% decline in the estimated glomerular filtration rate or end-stage renal disease). The receiver operating characteristic analysis determined the cut-off for high vs. low Max GD at 245.9 μm, and adding high Max GD to the MEST-C score significantly improved the model’s discrimination of renal outcomes at 5 and ≥10 years. Thus, including the Max GD in the Oxford classification of IgAN might increase its robustness and provide a more comprehensive prognostic system for clinical settings.

The number of nephrons in different glomerular diseases

Background

The total number of nephrons has been measured mainly from post-mortem studies and only in selected populations. Data from living subjects are scanty, and direct comparisons among different glomerular diseases are lacking. The present work exploits modern methodology to estimate the total nephron number in glomerulopathies with prevalent proteinuria/nephrotic syndrome versus glomerulopathies with nephritic syndrome (IgA nephropathy (IgAN), lupus nephritis), thus extending previous observations about the number and function of glomeruli in different physiological and pathological states.

Methods

This is a retrospective study based on one hundred and seven patients who have undergone renal biopsy. The glomerular density has been estimated from the biopsy specimens and the total cortical volume has been obtained from ultrasound recordings. Stereological methods have been applied to calculate the total number of nephrons and their volume. The correlation between clinical parameters and quantitative morphological data have studied using the Pearson correlation coefficient (r).

Results

The total number of nephrons inversely correlated with the systolic blood pressure (r = −0.4, p < 0.05). In proteinuric diseases, such as focal segmental glomerulo-sclerosis (FSGS), membranous nephropathy (MN) and diabetes, the change in estimated GFR (eGFR) directly correlated with the total number of non-sclerotic glomeruli (NSG) (r = 0.62, p < 0.01), whereas in nephritic syndrome no significant correlation was observed. The alterations in eGFR occurring in nephritic syndromes such as IgAN cannot be explained on the basis of the number of NSG.

Discussion

The fusion of the podocyte foot-processes that typically occurs in purely proteinuric diseases does not modify the glomerular filtration rate: therefore in these situations, the change in eGFR depends mainly on the number of available glomeruli. On the other side, the eGFR decrease occurring in nephritic syndromes, such as IgAN, cannot be explained simply on the basis of the number of NSG and likely depends on the substantial involvement of the mesangial axis. Future studies should verify whether these changes are reversible with appropriate therapy, thus reversing eGFR decrease.

The Kidney in Congenital Cyanotic Heart Disease

This column is supplied by Benjamin J. Lee, MD, MAS, an assistant professor of clinical medicine at both the Houston Methodist Institute for Academic Medicine and Weill Cornell Medical College. After earning his medical degree at Harvard Medical School, Dr. Lee completed a residency in internal medicine at the University of California, San Francisco (UCSF). He subsequently completed a nephrology fellowship at UCSF while simultaneously obtaining a Master of Advanced Study in clinical research from the UCSF Department of Epidemiology and Biostatistics. Dr. Lee is a Fellow of the American Society of Nephrology, a Certified Hypertension Specialist through the American Hypertension Specialist Certification Program, and a member of the American Society of Transplantation. He maintains his clinical practice with the Houston Kidney Consultants.

Synergistic Impact of Diabetes and Hypertension on the Progression and Distribution of Glomerular Histopathological Lesions

BACKGROUND

Diabetes and hypertension share renal histopathological features, such as arterial lesions and glomerular hypertrophy, that have not been investigated in relation to the blood pressure status of diabetic subjects. The severity of glomerular lesions varies across locations of the renal cortex, which may be further affected by diabetes and/or hypertension.

METHODS

Histopathological lesions in different parts of the renal cortex of autopsy kidneys were evaluated and analyzed based on medical histories of diabetes and hypertension.

RESULTS

This study included a total of 82 Japanese autopsies composed of normotensive nondiabetics (n = 31), hypertensive nondiabetics (n = 28), normotensive diabetics (n = 14), and hypertensive diabetics (n = 9). There were no differences in age, sex, renal function, or body size among groups. In both the superficial and juxtamedullary cortices, increased glomerular volume (GV) was significantly associated with either diabetes or hypertension. In addition, diabetes and hypertension showed a significant interaction with GV regardless of the cortical location. Values for global glomerulosclerosis (GGS) and arteriolar hyalinosis (AH) were associated with diabetes but not with hypertension. Only values for GGS consistently showed cortical surface superiority. The zonal distribution of AH, GV, or other diabetic glomerular lesions differed among the lesions depending on the presence or absence of hypertension.

CONCLUSIONS

These results imply that diabetes and hypertension synergistically enhance glomerular hypertrophy across all layers of the human renal cortex. The process is closely associated with the severity of GGS and AH predominantly associated with diabetes.

Current Management of Patients With Acquired Solitary Kidney

Persons with acquired solitary kidney, including those who have had a unilateral nephrectomy for living kidney donation, renal malignancies, or trauma, have decreased renal mass that leads to increased intraglomerular pressure and glomerular hyperfiltration. These physiologic adaptations of solitary kidney may exacerbate other preexisting and genetic conditions that could create a predisposition to or worsen glomerular pathologies, leading to unfavorable renal outcomes. Hence, these persons may benefit from special care and lifestyle modifications, including nutritional interventions. There is a lack of consensus and evidence for proper surveillance and management after nephrectomy, and misconceptions in both directions of having a “normal” versus “abnormal” kidney status may cause confusion among patients and healthcare providers pertaining to long-term kidney health monitoring and management. We have reviewed available data on the impact of lifestyle modifications, particularly nutritional measures, and pharmacologic interventions, on short- and long-term outcomes after nephrectomy. We recommend avoidance of excessively high dietary protein intake (>1 g/kg per day) and high dietary sodium intake (>4 grams/d), adequate dietary fiber intake from plant-based foods, a target body mass index of <30 kg/m² (in non-athletes and non-bodybuilders), and judicious management of risk factors of progressive chronic kidney disease (CKD), and future studies should help to better determine optimal care practices for these persons.

Electron microscopic findings suggestive of focal and segmental glomerulosclerosis in patients with steroid-resistant nephrotic syndrome

Distinction between minimal change disease and unsampled Focal Segmental Glomerulosclerosis is a challenging concept in kidney biopsy of patients with nephrotic syndrome with minimal histopathological findings. This study was performed to compare electron microscopic findings in patients with steroid-resistant nephrotic syndrome with minimal histopathological abnormalities and cases with Focal Segmental Glomerulosclerosis. This Cohort study was conducted in Cancer Institute, Imam Khomeini Hospital Complex, Tehran, Iran. Twenty patients with steroid-resistant nephrotic syndrome and minimal changes on the light microscopic study were selected as case group. Similarly, 20 patients with Focal Segmental Glomerulosclerosis were selected as the control group. Ultrastructural findings were re-evaluated and scored qualitatively (0-3+). In patients with minimal changes on light microscopic evaluation, clinical course of the disease was followed after 5 years. Mean ages of the patients (8 women and 12 men) in case and control groups were 12.9 and 15.9 years, respectively (p > 0.05). There was no significant difference in number of examined glomeruli and sampling from cortico-medullary junction area between the groups. The mean percentage of sclerotic glomeruli in control group was 15.4%. Tubular atrophy and interstitial fibrosis were more frequent in control patients. Podocyte proliferation, GBM duplication (involving more than 10% of capillary walls), and moderate to severe multifocal expansion of mesangial matrix were significantly more obvious in FSGS patient samples (p < 0.05). No statistically significant difference was found in severity of cytoplasmic vacuolization, GBM wrinkling and splitting between the groups. Most of (80%) the patients with minimal changes improved during the 5-year follow-up. Generally, we concluded that Podocyte proliferation, GBM remodeling, and moderate to severe mesangial matrix expansion are the most reliable findings on electron microscopic examination in favor of FSGS.

Volume Ratio of Glomerular Tufts to Bowman Capsules and Renal Outcomes in Nephrosclerosis

BACKGROUND

The concomitant appearance of glomerular collapse and enlargement is characteristic of the histological findings in nephrosclerosis. However, no previous study quantitatively examined the clinicopathological significance of this feature in patients with biopsy-proven nephrosclerosis.

METHODS

Renal biopsy specimens and follow-up data from nephrosclerosis patients with estimated glomerular filtration rates >30 ml/min/1.73 m2 at diagnosis were retrospectively reviewed. Mean volumes for glomerular tufts (GV) and Bowman capsules (BV) were separately calculated, based on the measurement of all areas of glomerular tufts and Bowman capsules in a cross-section of biopsy specimens. The G/B ratio was defined as the ratio of GV to BV. The doubling of serum creatinine levels (DSC) and the initiation of renal replacement therapies (end-stage renal disease (ESRD)) were examined as renal outcome indices.

RESULTS

A total of 67 patients with biopsy-proven nephrosclerosis were included. Clinicopathological findings at biopsy, other than GV, were comparable among all patients, irrespective of G/B ratio. Overall, 25 patients (37%) developed DSC and 9 (13%) developed ESRD during the median observation periods of 7.8 and 8.5 years, respectively. Renal survival curve analyses indicated a significantly worse prognosis for patients with a low G/B ratio, as compared with those with a high G/B ratio. Cox hazard analyses for DSC identified low G/B ratio as a significant predictor, but not low GV or BV.

CONCLUSIONS

These results suggest that the quantitative evaluation of G/B ratio may detect subtle abnormalities in the glomerulus, indicating the subsequent renal outcomes of nephrosclerosis patients.

Prevalence and associated factors of renal dysfunction and proteinuria in cyanotic congenital heart disease

BACKGROUND

Cyanotic nephropathy (CN), seen in 30-50% of patients with congenital cyanotic heart disease (CCHD), affects both tubular and glomerular function, resulting in proteinuria and azotemia. Microalbuminuria is an early marker for glomerular damage and an independent predictor of progressive renal disease.

METHODS

A cross-sectional study was conducted. A total of 116 patients aged 1 month to 15 years with CCHD at Chiang Mai University Hospital between 2015 and 2016 were assessed and 94 patients were enrolled. To determine the prevalence and associated factors of significant albuminuria in CCHD patients, baseline characteristics, oxygen saturation, surgery, hemoglobin (Hb), hematocrit (Hct), spot urine albumin, urine protein, and creatinine were obtained. Binary logistic-regression modeling was used to identify associated factors.

RESULTS

Prevalence of CN in children with CCHD was 58.51% and 92.55% according to albuminuria and proteinuria staging respectively. Prevalence of significant proteinuria, significant albuminuria, and decreased GFR was 88.30%, 41.49% and 31.91% respectively. Participants with significant albuminuria had fewer previous surgeries (p = 0.05), a longer waiting time for surgery (p = 0.02), enalapril usage (p = 0.04), pulmonary hypertension (p = 0.03), higher Hct z-score (p = 0.03) and lower platelet count (p = 0.001) compared with those without significant albuminuria. Using multivariate logistic regression analysis, waiting duration for surgery (p = 0.04), Hct >40% (p = 0.02), and platelet count <290,000/mm³ (p = 0.04) were predictive of microalbuminuria.

CONCLUSIONS

Cyanotic nephropathy can be detected in the first decade of life with the presentation of microalbuminuria. High Hct level and low platelet count were identified as a predictor of microalbuminuria, whereas early cardiac surgery decreased the risk of developing significant albuminuria.

Bowman Capsule Volume and Related Factors in Adults With Normal Renal Function

Introduction

Alterations in glomerular filtration can considerably influence the dynamics and functions of the Bowman capsule. Despite the potentially important role in maintaining normal renal functions, few studies have focused on Bowman capsule volume in normal human kidneys.

Methods

We analyzed specimens from biopsies performed 1 hour after kidney transplantation from living donors without apparent renal disease. The measurements of all cross-sectional areas of the Bowman capsules and glomerular capillaries were used to estimate the mean Bowman capsule volume (BV) and glomerular capillary volume (GV) in each subject. The G/B ratio was defined as the ratio of GV to BV. The morphometric findings were examined in relation to the clinical findings in donors just before kidney transplantation.

Results

We analyzed 37 adults with a mean creatinine clearance of 111 ml/min. The mean BV and GV of these subjects were 6.10 ± 2.46 × 10⁶ μm³ and 3.83 ± 1.52 × 10⁶ μm³, respectively. Both the BV and GV varied up to 6-fold and were significantly higher in elderly, obese, or hypertensive subjects in comparison to nonelderly, nonobese, or normotensive subjects, whereas the renal function of each subgroup was similar. The G/B ratio (0.63 ± 0.05) was unaffected, and BV and GV were strongly correlated regardless of these clinical factors (r = 0.980 [95% confidence interval = 0.961−0.990], P < 0.001).

Conclusion

In the normal adult kidney, there may be an optimal BV to GV ratio for maintaining effective filtration in a variety of clinical situations, including advanced age, obesity, and hypertension.

Nephrin Loss Can Be Used to Predict Remission and Long-term Renal Outcome in Patients With Minimal Change Disease

Introduction

Minimal change disease is a common cause of nephrotic syndrome. In general, patients with minimal change disease respond to corticosteroids and have excellent long-term renal survival. However, some patients have less favorable outcome. These patients are often thought to have progressed to focal segmental glomerulosclerosis. We previously reported that a segmental loss of podocyte markers is present before the development of focal segmental glomerulosclerosis in a rat model. Here, we investigated whether loss of podocyte marker nephrin can serve as a biomarker for predicting poor outcome in patients with minimal change disease.

Methods

We obtained 47 kidney biopsy samples from patients diagnosed with minimal change disease and stained sections with periodic acid−Schiff and for nephrin. Nephrin loss was scored by 2 independent researchers who were blinded to clinical outcome. Clinical data were collected retrospectively, and nephrin loss was correlated with clinical follow-up data.

Results

Nephrin loss was present in 34% of the biopsy samples. During follow-up, patients with nephrin loss achieved remission less frequently (61%) compared to patients without (96%) (P = 0.002). Moreover, 5-year eGFR was lower in the patients with renal nephrin loss. The risk of eGFR decreasing to < 60 ml/min per 1.73m² increased with each percentage of glomeruli with nephrin loss (hazard ratio = 1.044, 95% confidence interval = 1.02−1.07).

Conclusion

These results indicate that nephrin loss in patients with minimal change disease can help predict both remission and long-term renal outcome.

Practical Application of Columbia Classification for Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a heterogeneous clinicopathological entity. Two frameworks for the classification of FSGS have been described: etiologic and morphologic. The etiologic classification is distinguished among genetic, adaptive, virus-associated, drug-induced, and idiopathic types. Morphologic classification is commonly referred to as the Columbia classification published in 2004, which distinguishes five variants: collapsing, tip, cellular, perihilar, and not otherwise specified (NOS). This classification is based on light microscopic patterns with rigorously defined specific criteria, which can be applied to primary and secondary forms of FSGS, and has been widely used over the past 10 years both as a diagnostic and as a prognostic clinical tool. This paper defines common histopathological features of FSGS, distinguished characters among five variants, and points out the confusion about terminology of variants, because most were proposed in the past with different definitions. Despite good interobserver reproducibility of this classification system, difficulty in its application may arise in the interpretation of lesions with mixed features of more than one variant in the same tissue specimen and with late lesions, because other variants may evolve into the NOS variant over time.

Glomerular Function and Structure in Living Donors: Lessons from Single Nephron Studies

One third of the kidney transplants performed in the USA come from living kidney donors. The long-term outcome of healthy individuals who donate kidneys is mostly excellent, although recent studies have suggested that living donation is associated with a small absolute increase in the risk of end stage renal failure. Much of our understanding about the progression of kidney disease comes from experimental models of nephron loss. For this reason, living kidney donation has long been of great interest to renal physiologists. This review will summarize the determinants of glomerular filtration and the physiology that underlies post-donation hyperfiltration. We describe the 'remnant kidney' model of kidney disease and the reasons why such progressive kidney disease very rarely ensues in healthy humans following uninephrectomy. We also review some of the methods used to determine glomerular number and size and outline their associations.

A computational model of flow and species transport in the mesangium

A variety of macromolecules accumulate in the glomerular mesangium in many different diseases, but the physics of the transport of these molecules within the mesangial matrix has not been extensively studied. We present a computational model of convection and diffusion within the porous mesangial matrix and apply this model to the specific instance of immunoglobulin A (IgA) transport in IgA nephropathy. We examine the influence of physiological factors including glomerular basement membrane (GBM) thickness and mesangial matrix density on the total accumulation of IgA. Our results suggest that IgA accumulation can be understood by relating convection and diffusion, thus demonstrating the importance of intrinsic glomerular factors.

Glomerular Hypertrophy Is a Risk Factor for Relapse in Minimal Change Disease Patients

BACKGROUND/AIMS

Patients with minimal change disease (MCD) have a high relapse rate, which results in many complications. Identifying the risk factors for relapse is crucial, but little is known about these factors. Therefore, we performed the current study to determine the factors related to relapse in this patient population.

METHODS

We retrospectively analyzed 51 adult patients with biopsy-proven primary MCD treated between 2003 and 2013. The demographic, physiologic, laboratory and therapeutic data were gathered from the electronic medical records database. Lesions of the glomerulus, tubulointerstitium and vasculature were analyzed for associations with relapse.

RESULTS

During a median 50.9 months, 96.1% (49 of 51) of patients had achieved complete remission, and the rest ultimately achieved at least partial remission. A total of 56.9% (29 of 51) patients experienced at least 1 episode of relapse after the first remission. Patients with relapse had a higher rate of glomerular hypertrophy (GH; 34.5%) than those without relapse (9.1%; p < 0.05). After adjusting for confounders, GH was associated with increased odds of relapse (OR 15.992; 95% CI 1.537-166.362; p = 0.02). In a subgroup analysis according to median age, sex and tubulointerstitial (TI) lesions, the association between GH and relapse was evident only in men and in the group with TI lesions.

CONCLUSION

GH is associated with relapse in adult patients with MCD, particularly in men and in those with TI lesions. Frequent monitoring and early intervention are needed in these groups. Future large prospective cohort studies are needed to confirm the study results.

Causes and pathogenesis of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) describes both a common lesion in progressive kidney disease, and a disease characterized by marked proteinuria and podocyte injury. The initial injuries vary widely. Monogenetic forms of FSGS are largely due to alterations in structural genes of the podocyte, many of which result in early onset of disease. Genetic risk alleles in apolipoprotein L1 are especially prevalent in African Americans, and are linked not only to adult-onset FSGS but also to progression of some other kidney diseases. The recurrence of FSGS in some transplant recipients whose end-stage renal disease was caused by FSGS points to circulating factors in disease pathogenesis, which remain incompletely understood. In addition, infection, drug use, and secondary maladaptive responses after loss of nephrons from any cause may also cause FSGS. Varying phenotypes of the sclerosis are also manifest, with varying prognosis. The so-called tip lesion has the best prognosis, whereas the collapsing type of FSGS has the worst prognosis. New insights into glomerular cell injury response and repair may pave the way for possible therapeutic strategies.

A potential role for mechanical forces in the detachment of podocytes and the progression of CKD

Loss of podocytes underlies progression of CKD. Detachment of podocytes from the glomerular basement membrane (GBM) rather than apoptosis or necrosis seems to be the major mechanism of podocyte loss. Such detachment of viable podocytes may be caused by increased mechanical distending and shear forces and/or impaired adhesion to the GBM. This review considers the mechanical challenges that may lead to podocyte loss by detachment from the GBM under physiologic and pathophysiologic conditions, including glomerular hypertension, hyperfiltration, hypertrophy, and outflow of filtrate from subpodocyte spaces. Furthermore, we detail the cellular mechanisms by which podocytes respond to these challenges, discuss the protective effects of angiotensin blockade, and note the questions that must be addressed to better understand the relationship between podocyte detachment and progression of CKD.

Clinicopathological assessment of the nephron number

Recent studies have demonstrated much larger variability in the total number of nephrons in normal populations than previously suspected. In addition, it has been suggested that individuals with a low nephron number may have an increased lifetime risk of hypertension or renal insufficiency, emphasizing the importance of evaluating the nephron number in each individual. In view of the fact that all previous reports of the nephron number were based on analyses of autopsy kidneys, the identification of surrogate markers detectable in living subjects is needed in order to enhance understanding of the clinical significance of this parameter. In this review, we summarize the clinicopathological factors and findings indicating a reduction in the nephron number, focusing particularly on those found at the time of a preserved renal function.

The role of a low glomerular density and being overweight in the etiology of proteinuria in CKD patients without known glomerular diseases

BACKGROUND

Among the proteinuric patients with chronic kidney disease (CKD) who undergo a renal biopsy, we sometimes encounter those who cannot be classified as having a known primary or secondary glomerular disease. The pathogenesis and pathophysiology of these CKD patients have not been sufficiently elucidated.

METHODS

We recruited 34 proteinuric patients without known glomerular diseases. The glomerular volumes (GV) of the biopsy specimens from those patients were determined by a morphometric analysis. Glomerular hypertrophy (GH) was defined as having more than 3.6 × 10(6) μm(3). The patients were divided in two groups: those with GH (Group 1) and those without GH (Group 2). We compared the clinical and pathological parameters between Group 1 and Group 2, and among the three groups of patients: non-obese, overweight and obese group.

RESULTS

The patients with Group 1 had significantly higher values for the proportion of males, the body mass index (BMI), uric acid and significantly lower values for the glomerular density (GD). Of note, a multivariate regression analysis revealed that sex, the BMI and GD were significant factors correlated with the mean GV. The values for the mean GV were significantly higher in the overweight and obese groups as compared to the non-obese group, and the values for the GD were significantly lower in the obese group than in the non-obese group.

CONCLUSIONS

We identified a subgroup of patients who were characterized as having a high BMI and GV, and a low GD among the proteinuric CKD patients without known glomerular diseases.

Structural analysis of how podocytes detach from the glomerular basement membrane under hypertrophic stress

Podocytes are lost by detachment from the GBM as viable cells; details are largely unknown. We studied this process in the rat after growth stimulation with FGF-2. Endothelial and mesangial cells responded by hyperplasia, podocytes underwent hypertrophy, but, in the long run, developed various changes that could either be interpreted showing progressing stages in detachment from the GBM or stages leading to a tighter attachment by foot process effacement (FPE). This occurred in microdomains within the same podocyte; thus, features of detachment and of reinforced attachment may simultaneously be found in the same podocyte. (1) Initially, hypertrophied podocytes underwent cell body attenuation and formed large pseudocysts, i.e., expansions of the subpodocyte space. (2) Podocytes entered the process of FPE starting with the retraction of foot processes (FPs) and the replacement of the slit diaphragm by occluding junctions, thereby sealing the filtration slits. Successful completion of this process led to broad attachments of podocyte cell bodies to the GBM. (3) Failure of sealing the slits led to gaps of varying width between retracting FPs facilitating the outflow of the filtrate from the GBM. (4) Since those gaps are frequently overarched by broadened primary processes, the drainage of the filtrate into the Bowman's space may be hindered leading to the formation of small pseudocysts associated with bare areas of GBM. (5) The merging of pseudocysts created a system of communicating chambers through which the filtrate has to pass to reach Bowman's space. Multiple flow resistances in series likely generated an expansile force on podocytes contributing to detachment. (6) Such a situation appears to proceed to complete disconnection generally of a group of podocytes owing to the junctional connections between them. (7) Since such groups of detaching podocytes generally make contact to parietal cells, they start the formation of tuft adhesions to Bowman's capsule.

Podocyte effacement closely links to suPAR levels at time of posttransplantation focal segmental glomerulosclerosis occurrence and improves with therapy

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) recurs after kidney transplantation in more than 30% of cases and can lead to allograft loss. Serum soluble urokinase-type plasminogen activator receptor (suPAR) is implicated in the pathogenesis of native and recurrent FSGS.

METHODS

We conducted a retrospective study of 25 adults with posttransplantation FSGS. We investigated the relationship between suPAR levels and podocyte changes and the impact of therapy on podocyte structure. We assessed response to therapy by improvement in proteinuria, allograft function, and resolution of histologic changes.

RESULTS

A median (interquartile range) of 15 (10-23) plasmapheresis sessions was administered; 13 of the subjects also received rituximab. Median pretreatment suPAR levels were higher among those with severe (≥75%) versus those with mild (≤25%) podocyte foot process effacement (13,030 vs. 4806 pg/mL; P=0.02). Overall, mean±SD of proteinuria improved from 5.1±3.8 to 2.1±2.8 mg/dL (P=0.003), mean podocyte effacement decreased from 57%±33% to 22%±22% (P=0.0001), estimated glomerular filtration rates increased from median (interquartile range) of 32.9 (20.6-44.2) to 39.3 (28.8-63.4; P<0.0001), and suPAR levels decreased from a median of 6.781 to 4.129 pg/mL (P=0.02) with therapy.

CONCLUSIONS

Podocyte effacement is the first pathologic manifestation of FSGS after transplantation. The degree of podocyte effacement correlates with suPAR levels at time of diagnosis. Response to therapy results in significant reduction of suPAR levels and complete or significant improvement of podocyte effacement.

Parietal epithelial cell activation marker in early recurrence of FSGS in the transplant

BACKGROUND AND OBJECTIVES

Podocyte loss is key in glomerulosclerosis. Activated parietal epithelial cells are proposed to contribute to pathogenesis of glomerulosclerosis and may serve as stem cells that can transition to podocytes. CD44 is a marker for activated parietal epithelial cells. This study investigated whether activated parietal epithelial cells are increased in early recurrent FSGS in transplant compared with minimal change disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

CD44 staining in renal allograft biopsies from 12 patients with recurrent FSGS was performed and compared with native kidneys with minimal change disease or FSGS and normal control native and transplant kidneys without FSGS. CD44+ epithelial cells along Bowman's capsule in the parietal epithelial cell location and over the glomerular tuft in the visceral epithelial cell location were assessed.

RESULTS

Cases with early recurrent FSGS manifesting only foot process effacement showed significantly increased CD44+ visceral epithelial cells involving 29.0% versus 2.6% of glomeruli in minimal change disease and 0% in non-FSGS transplants. Parietal location CD44 positivity also was numerically increased in recurrent FSGS. In later transplant biopsies, glomeruli with segmental lesions had more CD44+ visceral epithelial cells than glomeruli without lesions.

CONCLUSIONS

Parietal epithelial cell activation marker is significantly increased in evolving FSGS versus minimal change disease, and this increase may distinguish early FSGS from minimal change disease. Whether parietal epithelial cell activation contributes to pathogenesis of sclerosis in idiopathic FSGS or is a regenerative/repair response to replace injured podocytes awaits additional study.

Tubulointerstitial injury and the progression of chronic kidney disease

In chronic kidney disease (CKD), once injury from any number of disease processes reaches a threshold, there follows an apparently irreversible course toward decline in kidney function. The tubulointerstitium may play a key role in this common progression pathway. Direct injury, high metabolic demands, or stimuli from various other forms of renal dysfunction activate tubular cells. These, in turn, interact with interstitial tissue elements and inflammatory cells, causing further pathologic changes in the renal parenchyma. The tissue response to these changes thus generates a feed-forward loop of kidney injury and progressive loss of function. This article reviews the mechanisms of this negative cycle mediating CKD.

Laparoscopic partial nephrectomy under warm ischemia reduces the glomerular density in a pig model

PURPOSE

To investigate the number of nephrons, using unbiased stereological method, after warm ischemia for laparoscopic partial nephrectomy in a pig model.

METHODS

Fourteen pigs underwent left laparoscopic partial nephrectomy, and four animals were used as controls (not operated). Renal vessels were clamped, and 25% of kidney length was resected. The animals were euthanized after 2 weeks, and the kidneys were collected. Thus, we analyzed 14 left kidneys submitted to warm ischemia, 14 right kidneys from the same animals but not submitted to ischemia and eight kidneys from control animals. Renal fragments were processed using routine histological methods. The total operative time and the time of warm ischemia were recorded. Glomerular mean volume and glomerular density were quantified by stereological methods. Creatinine serum levels were assessed preoperatively and before euthanasia.

RESULTS

Surgical time was 71 ± 17 minutes, and ischemia time was 16 ± 5 minutes. The mean glomerular volume in the left kidneys was higher when compared with controls and to right kidneys (p<0.05). In addition, the glomerular density was reduced in the left kidneys (p<0.05) when compared with controls and right kidneys. Nevertheless, creatinine serum levels after 2 weeks of surgery were not different from the preoperative levels. No difference was found for stereological measurements between controls and right kidneys.

CONCLUSION

Stereological determination of glomerular density can be used as an accurate and objective method for studies regarding renal damage from ischemia. Warm ischemia during laparoscopic partial nephrectomy in pigs determined a significant reduction of glomerular density in the ipsilateral remaining parenchyma.

Glomerular density-associated changes in clinicopathological features of minimal change nephrotic syndrome in adults

BACKGROUND

Differences in nephron number and/or glomerular size between individuals, in relation to intrauterine growth retardation or low birth weight, have been suggested to affect the clinical course of minimal change nephrotic syndrome (MCNS) in children. However, no previous study has investigated the potential influences of these histological variables on the clinical course of adult patients with MCNS.

METHODS

The glomerular density (GD; the number of non-sclerotic glomeruli per renal cortical area) and the glomerular volume (GV) were evaluated using renal biopsy specimens from adult patients with a histological diagnosis of MCNS (n = 50). Relationships between these variables and clinicopathological features, including the initial response to corticosteroid therapy, were analyzed.

RESULTS

Both the GD (1.5-6.5/mm(2)) and the GV (1.2-4.4 × 10(6) μm(3)) showed about 4-fold variations, and a close inverse correlation was observed between these two variables. Notably, the MCNS patients with a low GD showed a trend towards having similar clinicopathological characteristics as patients with a histological diagnosis of focal segmental glomerular sclerosis, as compared to the MCNS patients with a high GD. In addition, during the initial treatment with corticosteroids, the number of patients achieving complete remission was significantly lower in the MCNS patients with a low GD than that in the MCNS patients with a high GD.

CONCLUSION

These results suggest that the GD in renal biopsies may be an important determinant of the glomerular size variability, and can therefore influence the clinical phenotype, such as the response to corticosteroid therapy, in adult patients with MCNS.

Estimating individual glomerular volume in the human kidney: clinical perspectives

BACKGROUND

Measurement of individual glomerular volumes (IGV) has allowed the identification of drivers of glomerular hypertrophy in subjects without overt renal pathology. This study aims to highlight the relevance of IGV measurements with possible clinical implications and determine how many profiles must be measured in order to achieve stable size distribution estimates.

METHODS

We re-analysed 2250 IGV estimates obtained using the disector/Cavalieri method in 41 African and 34 Caucasian Americans. Pooled IGV analysis of mean and variance was conducted. Monte-Carlo (Jackknife) simulations determined the effect of the number of sampled glomeruli on mean IGV. Lin's concordance coefficient (R(C)), coefficient of variation (CV) and coefficient of error (CE) measured reliability.

RESULTS

IGV mean and variance increased with overweight and hypertensive status. Superficial glomeruli were significantly smaller than juxtamedullary glomeruli in all subjects (P < 0.01), by race (P < 0.05) and in obese individuals (P < 0.01). Subjects with multiple chronic kidney disease (CKD) comorbidities showed significant increases in IGV mean and variability. Overall, mean IGV was particularly reliable with nine or more sampled glomeruli (R(C) > 0.95, <5% difference in CV and CE). These observations were not affected by a reduced sample size and did not disrupt the inverse linear correlation between mean IGV and estimated total glomerular number.

CONCLUSIONS

Multiple comorbidities for CKD are associated with increased IGV mean and variance within subjects, including overweight, obesity and hypertension. Zonal selection and the number of sampled glomeruli do not represent drawbacks for future longitudinal biopsy-based studies of glomerular size and distribution.

[Evaluation of a renal biopsy: what information is important for nephrologists?]

A kidney biopsy is an important and frequently used diagnostic tool in routine nephrology. In order to obtain relevant clinical information from a renal biopsy close cooperation between clinicians and pathologists is mandatory. The better the information obtained from nephrologists and the better the understanding by nephrologists and the quality of the kidney biopsy, the more rewarding is the information from pathologists. The following paper will discuss some practical aspects regarding the interaction between nephrology and pathology which may not be known or poorly handled and may thus cause misunderstanding. In order to facilitate interaction between clinicians and pathologists some guidelines concerning the procedure and work-up of routine kidney biopsies have been established and will be discussed in detail.

Problems with 'focal segmental glomerulosclerosis'

The term 'focal segmental glomerulosclerosis (FSGS)' has been applied to many different conditions. All classifications of 'FSGS', including those describing 'variants', perpetuate the misconceptions that the entities included have something in common and that the term 'FSGS' has some value. With a rigorous approach to renal biopsies showing segmental lesions, especially with knowledge of clinical circumstances and with detailed analysis of features such as the appearance of lesions and their position within glomeruli, a pathologist can provide information that is clinically more useful than merely the bald diagnosis 'FSGS'. More precise terms should be used. 'Overload changes' can be used to describe the changes seen in reduced renal mass. 'Tip changes' can be seen in many conditions and are not a disease in themselves. 'The glomerular tip lesion as originally defined' means the occurrence of tip changes in otherwise normal glomeruli, in the nephrotic syndrome. 'Early classical segmental sclerosing glomerulopathy' is the combination of tip changes and otherwise abnormal glomeruli, in the nephrotic syndrome. 'Late classical segmental sclerosing glomerulopathy' means segmental lesions at various sites within glomeruli, in the nephrotic syndrome. 'Collapsing glomerulopathy' is distinctive, and its inclusion in classifications emphasises the lack of specificity of 'FSGS'.

Association of kidney function and metabolic risk factors with density of glomeruli on renal biopsy samples from living donors

OBJECTIVE

To test the hypothesis that kidney function and metabolic risk factors are associated with glomerular density on renal biopsy samples from healthy adults.

PATIENTS AND METHODS

This study compared glomerular density with predonation kidney function, blood pressure, and metabolic risk factors in living kidney donors at Mayo Clinic in Rochester, MN, from May 10, 1999, to February 4, 2009. During implantation of the kidney allograft, an 18-gauge core needle biopsy sample of the renal cortex was obtained, sectioned, and examined by pathologists. Glomerular density was determined by the number of glomeruli (normal and sclerotic) divided by area of cortex.

RESULTS

The study sample of 1046 kidney donors had a mean of 21 glomeruli (0.8 sclerotic glomeruli) and a glomerular density of 2.3 glomeruli per square millimeter. In a subset of 54 donors, glomerular density inversely correlated with the mean glomerular area (r(s) = -0.28). Independent predictors of decreased glomerular density were older age, increased glomerular filtration rate, family history of end-stage renal disease, increased serum uric acid, and increased body mass index. Increased urine albumin excretion, hypertension, decreased high-density lipoprotein cholesterol, and metabolic syndrome were also associated with decreased glomerular density after age-sex adjustment. These associations were not explained by the presence of glomerulosclerosis, tubular atrophy, interstitial fibrosis, or arteriosclerosis on the renal biopsy sample. In older donors, decreased glomerular density was attenuated by an increased prevalence of glomerulosclerosis and tubular atrophy.

CONCLUSION

Decreased glomerular density is associated with many different kidney function and metabolic risk factors among relatively healthy adults and may represent an early state of increased risk of parenchymal injury.

Maximal glomerular diameter as a 10-year prognostic indicator for IgA nephropathy

BACKGROUND

Although there have been many reports on clinicopathological studies of immunoglobulin A nephropathy (IgAN), reliable outcome predictors are still lacking. We therefore assessed maximal glomerular diameter (Max GD), an indicator of glomerular size, as a predictor of the long-term evolution of renal histopathology.

METHODS

Forty-three adult patients, diagnosed with IgAN, who had estimated glomerular filtration rate (eGFR) ≥50 mL/min/1.73 m(2), were enrolled in this study. Prognostic variables for renal survival were examined by using the multivariate Cox proportional hazards method. The optimal cut-off value of Max GD was 242.3 μm (AUC = 0.78, sensitivity = 62.5%, specificity = 81.5%) by using receiver operating characteristics analysis. In order to assess the characteristics of glomerular hypertrophy, we divided the cases into two groups according to the Max GD value (Group A, ≥242 μm; Group B, <242 μm). Renal survival was also assessed by Kaplan-Meier curves with the log-rank test.

RESULTS

The Max GD was significantly correlated with age, body mass index and serum triglyceride levels at the time of renal biopsy. During the 10-year follow-up period, the Max GD was significantly correlated with eGFR decline per year, and proteinuria, but not with hematuria. A multiple regression analysis by the Cox method adjusted for age, sex and eGFR showed that the Max GD values were significantly associated with a 1.5-fold increase in serum creatinine (Cr) values (hazard ratio = 1.04, P = 0.03). Renal function in 66.7% of the patients whose Max GD was ≥242 μm had at least a 1.5-fold increase in their serum Cr value at the 10-year follow-up examination (log-rank, P = 0.003).

CONCLUSIONS

The results of this study suggest that Max GD is a simple quantitative prognostic indicator of the disease progression in IgAN patients.

Towards a definition of glomerulomegaly: clinical-pathological and methodological considerations

BACKGROUND

Glomerulomegaly, the abnormal enlargement of glomeruli, has been related to an increased risk of glomerulosclerosis, but the degree of enlargement that constitutes glomerulomegaly has not been defined.

METHODS

The principal stereological methods for estimating glomerular volume are [1] the disector/Cavalieri method that is considered the 'gold standard' for measuring individual glomerular volume (IV(glom)) and [2] the disector/fractionator technique that estimates average glomerular volume (V(glom)) together with total glomerular number (N(glom)) for the entire kidney. The two methods produce different estimates with V(glom) consistently exceeding IV(glom). This study compares glomerular volumes obtained by the two methods in autopsy kidneys of 39 African American and 34 US white adult males, and correlates the values with N(glom), body mass index (BMI), hypertension, glomerulosclerosis and race, factors known or thought to influence glomerular volume.

RESULTS

For the smallest glomeruli, V(glom) was 25% larger than IV(glom) with the difference increasing to over 50% for kidneys with the largest glomeruli. Both V(glom) and IV(glom) showed significant inverse correlations with N(glom) and significant direct correlations with BMI and hypertension. African Americans had larger IV(glom) and V(glom) than whites, but only IV(glom) was significant. The 90th percentile for IV(glom) was 6.81 μm(3) × 10(6) and 13.10 μm(3) × 10(6) for V(glom), but larger glomerular size did not separate hypertensive from non-hypertensive subjects nor did it show any significant relationship to glomerulosclerosis. While V(glom) overestimated glomerular size compared with IV(glom), both measurements demonstrated similar relationships to factors influencing glomerular volume.

CONCLUSIONS

With neither method could glomerulomegaly, the abnormal enlargement of glomerular size predisposing to glomerulosclerosis, be determined.

Induction of podocyte VEGF164 overexpression at different stages of development causes congenital nephrosis or steroid-resistant nephrotic syndrome

The tight regulation of vascular endothelial growth factor-A (VEGF-A) signaling is required for both the development and maintenance of the glomerular filtration barrier, but the pathogenic role of excessive amounts of VEGF-A detected in multiple renal diseases remains poorly defined. We generated inducible transgenic mice that overexpress podocyte VEGF164 at any chosen stage of development. In this study, we report the phenotypes that result from podocyte VEGF164 excess during organogenesis and after birth. On doxycycline induction, podocin-rtTA:tet-O-VEGF164 mice express twofold higher kidney VEGF164 levels than single transgenic mice, localized to podocytes. Podocyte VEGF164 overexpression during organogenesis resulted in albuminuria at birth and was associated with glomerulomegaly, uniform podocyte effacement, very few and wide foot processes joined by occluding junctions, almost complete absence of slit diaphragms, and swollen endothelial cells with few fenestrae as revealed by transmission electron microscopy. Podocyte VEGF164 overexpression after birth caused massive albuminuria in 70% of 2-week-old mice, glomerulomegaly, and minimal changes on light microscopy. Transmission electron microscopy showed podocyte effacement and fusion and morphologically normal endothelial cells. Podocyte VEGF164 overexpression induced nephrin down-regulation without podocyte loss. VEGF164-induced abnormalities were reversible on removal of doxycycline and were unresponsive to methylprednisolone. Collectively, the data suggest that moderate podocyte VEGF164 overexpression during organogenesis results in congenital nephrotic syndrome, whereas VEGF164 overexpression after birth induces a steroid-resistant minimal change like-disease in mice.

Focal segmental glomerulosclerosis in idiopathic membranous glomerulonephritis: a clinico-pathological and stereological study

BACKGROUND

The phenomenon of focal segmental glomerulosclerosis (FSGS) in idiopathic membranous glomerulonephritis (IMGN) has not been adequately studied. There is also a paucity of detailed glomerular morphometric and stereologic analyses data on renal biopsy in this association.

METHODS

Twenty-three (23) patients with IMGN and superimposed FSGS were compared to 35 patients with IMGN alone with respect to the clinical and laboratory features, light microscopic findings and stereologic parameters (glomerular cross-sectional area and estimated glomerular volume).

RESULTS

In the clinical parameters, patients with IMGN-FSGS had a significantly higher incidence of hypertension, raised serum creatinine and microscopic haematuria. The mean 24-h urinary protein excretion was higher in the group with IMGN-FSGS (7.4 +/- 1.36 g) as compared to IMGN alone (3.85 +/- 0.7 g, P < 0.001, Mann-Whitney test). On light microscopy, biopsies with IMGN-FSGS frequently had mesangial hypercellularity and more extensive tubulo-interstitial disease than those with IMGN alone. Stereological analysis showed that the non-sclerosed glomeruli in biopsies with IMGN-FSGS had a higher mean cross-sectional area (185466.7 +/- 32493.3 micro(2)) and higher estimated volume (855200 +/- 152640 micro(3)) as compared to glomeruli in cases with IMGN alone (76000 +/- 14719.2 micro(2) and 576666.7 +/- 131233.3 micro(3), respectively).

CONCLUSION

The present study is probably the first systematic analysis of stereologic parameters in renal biopsies of IMGN with FSGS. Our results objectively demonstrate the glomerular enlargement in the non-sclerosed glomeruli in cases of IMGN with FSGS. This detection of enlarged glomeruli may serve to alert the renal pathologist to the possibility of coexisting FSGS, which is a poor prognostic factor in IMGN.