| Abstract|| |
Only a few studies describe histopathological changes in renal biopsies performed in pediatric patients. This study was conducted to identify an association between morphometric data in renal biopsies and renal function of these patients. Fifty-nine individuals with ages between 2 and 18 years old were selected, who were divided into six groups consisting of frequent nephropathies in children and adolescents and one control group. Proteinuria, urea, and creatinine values of the patients were recorded. Interactive image analysis software Leica QWin[®]was used for morpho- metric analysis of Bowman's capsule, glomerular capillary tuft, and Bowman's space area. The mean glomerular tuft area was higher in the membranous glomerulopathy group than in the podo- cytopathy group (57,101 ± 25,094 vs. 27,420 c ± 6279 µm2; P <0.05). The median of Bowman's space area was higher in the control group than in the podocytopathy group and in the thin basement membrane/Alport syndrome group [12,210 (7676-26,945) vs. 5801 (3031-7852) µm2; P <0.01 and 12210 (7676-26,945) vs. 4183 (3797-7992) µm2; P <0.01, respectively]. There was a positive and significant correlation between Bowman's capsule area and the levels of proteinuria, creatinine, and urea of the patients, as well as between the glomerular tuft area and the levels of proteinuria, creatinine, and urea in the patients, regardless of their nephropathy. Glomerular morphometry may contribute to the diagnosis of some glomerulopathies and the association between glomerular morphometric parameters, and laboratory data may promote a better understanding of the prognosis of these patients.
|How to cite this article:|
Marini MB, Rocha LP, Machado JR, Ramalho FS, dos Reis MA, Corrêa RR. Contribution of glomerular morphometry to the diagnosis of pediatric nephropathies. Saudi J Kidney Dis Transpl 2016;27:493-9
|How to cite this URL:|
Marini MB, Rocha LP, Machado JR, Ramalho FS, dos Reis MA, Corrêa RR. Contribution of glomerular morphometry to the diagnosis of pediatric nephropathies. Saudi J Kidney Dis Transpl [serial online] 2016 [cited 2018 Nov 15];27:493-9. Available from: http://www.sjkdt.org/text.asp?2016/27/3/493/182382
| Introduction|| |
Renal biopsy is performed only infrequently among children since most cases in this age group have minimal change disease (MCD) as the underlying glomerulonephritis, which usually responds to steroid therapy.As a result, there are only a few studies describing histopatho- logical changes in renal biopsies performed in pediatric patients and correlating the findings as prognostic factors.,
Morphometry has now become a useful ad- junct to the diagnostic armamentarium of light, immunofluorescence, and electron microscopy, as it provides a deep insight into quantitative parameters of nephropathies.Introduction of computer-assisted digital image capturing and analysis has opened a new way to analyze renal biopsies. The potential of using this new quantitative information for the understanding of the pathogenesis of many of these glomerular lesions or for better prognostic information has not yet been fully elucidated.
]Improved histological and morphometric analysis of glomeruli in renal biopsies of pedia- tric patients with frequent nephropathies, and the association between morphological data and renal function may promote a clearer picture of diagnostic parameters in these patients.
| Materials and Methods|| |
This study was approved by the Triβngulo Mineiro Federal University Research Ethics Committee on October 29, 2010, under appro- val number 1740. Once the biopsies were re- quested, information regarding established la- boratory parameters such as proteinuria, urea, and creatinine of the patients were recorded. Their analysis is essential for the pediatric nephrologists.Moreover, creatinine clearance remains one of the most widely used markers in the evaluation of renal function.
Children aged 2-18 years, who underwent renal biopsy between 1996 and 2010 were included in the study. We selected 48 individuals that were divided into six groups according to the frequent nephropathies in pediatric patients:podocytopathy [focal segmental glomeruloscle- rosis (FSGS)/MCD] (n = 10), lupus nephritis (n = 10), Berger's disease (n = 10), thin basement membrane disease/Alport syndrome (n = 5), acute diffuse glomerulonephritis (ADGN) (n = 8), and membranous glomerulo-pathy (n = 5). The data of the control group (n = 11) came from autopsies performed in 2-18-year-old indi- viduals that did not have renal changes.
All the groups were matched according to age. Anatomopathological diagnosis of all cases was performed by a single nephropathologist. The representativeness of the number of cases in each group was verified in accordance with Motulsky, and in all analyzes performed in this study, it was found that the number of cases was representative.
Glomerular morphometry was performed by analysis of histological sections stained with hematoxylin and eosin. Only glomeruli that had vascular or urinary poles were analyzed because these characteristics showed that the histolo- gical section had been performed approximately in the center of the glomeruli. We used an inter- active image analyzing system from Leica Microsystems®, Leica QWin® (Wetzlar, Germany) for morphometric analysis of glo- meruli. Bowman's capsule area and glomerular capillary tuft were analyzed using a 40× objec- tive at a total magnification of 1250×. Two mea- surements were made in each captured image: First, we outline Bowman's capsule and, then, the area of the glomerular capillary tuft. Bow- man's space area was obtained by subtracting the glomerular capillary tuft area from Bowman's capsule area. Then, the areas of these three glomerular regions were expressed in μm.
Statistical analysis was performed used Graph Pad Prism 5.00 software (San Diego, CA, USA). Among variables with normal distribu-tion and similar variances, ANOVA test (F) and, subse- quently, Tukey's test were used. In this case, the results were expressed as mean ± standard deviation. Other-wise, Kruskal-Wallis test (H) and, subsequently, Dunn's test were used. In this instance, the results were expressed as median (minimum - maximum). The correlation bet- ween two variables with nonnormal distribution was analyzed using Spearman (rS) test. The differences in which the P <0.05 were consi- dered statistically significant.
| Results|| |
There was no significant difference between groups regarding Bowman's capsule area. The podocytopathy group (FSGS/MCD) presented the mean glomerular tuft area lower than all other groups. However, significant differences were observed only between membranous glo- merulopathy group and podocytopathy group (FSGS/MCD) (57,101 ± 25,094 vs. 27,420 ± 6279 µm; P <0.05). The median of Bowman's space area was higher in the control group when compared to all other groups. Never- theless, results with significant differences were observed only when control group were com- pared with podocytopathy group (FSGS/MCD) and thin basement membrane/Alport syndrome group [12,210 (7676-26,945) vs. 5801 (3031-7852) µm; P <0.01 and 12,210 (7676-26,945) vs. 4183 (3797-7992µm; P <0.01, respec- tively] [Figure 1], [Table 1].
|Figure 1. Comparison of the glomerular tuft and Bowman's space area of pediatric patients with different nephropathies. (a) Patient of control group (final magnification of ×1.250), (b) patient with thin membrane/Alport syndrome (final magnification of ×1.250), (c) patient with podocytopathy (focal segmental glomerulosclerosis/ minimal change disease) (final magnification of ×1.250), (d) patient with membranous glomerulopathy (final magnification of ×1.250), (e) comparison of the glomerular tuft area between the different nephropathies, (f) comparison of the Bowman's space area between the different nephropathies.|
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|Table 1. Analysis of the Bowman's capsule, glomerular tuft, and Bowman's space area|
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There was a positive and significant corre- lation between Bowman's capsule area and the levels of proteinuria, creatinine, and urea of the patients, as well as between the glomerular tuft area and the levels of proteinuria, creatinine, and urea in the patients, regardless of their nephropathy [Figure 2]. There was no corre- lation between Bowman's space area and the levels of proteinuria, creatinine, and urea in the patients, regardless of their nephropathy.
|Figure 2. Correlation between glomerular morphometric parameters and clinical data of pediatric patients with different nephropathies: (A) the Bowman's capsule area and proteinuria, (B) the glomerular tuft area and proteinuria, (C) the Bowman's capsule area and creatinine, (D) the glomerular tuft area and creatinine, (E) the Bowman's capsule area and urea, (F) the glomerular tuft area and urea|
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| Discussion|| |
Some diseases have morphological and clin- ical similarities, and therefore, the differentia- tion between these diseases by microscopic and ultrastructural analysis becomes difficult. In this study, two groups shared differential diagnosis of two diseases: The MCD or FSGS group because in some cases, the focal sclerosis of FSGS was not seen in the sample. Moreover, both are associated with severe proteinuria or nephrotic syndrome, and the main ultra struc- tural characteristic is the flattening of pedicels.The thin basement membrane disease and Alport syndrome group also have several simi- larities such as the fact that both are hereditary disorders characterized by structural changes in the glomerular basement membrane and have persistent hematuria as a typical clinical sign.Therefore, it is extremely important to develop new techniques to differentiate the diseases.
In this study, we observed that the membra- nous glomerulopathy group had a higher mean of glomerular tuft area than the podocytopathy group (FSGS/MCD). Membranous glomerulo- pathy is characterized by glomerular capillary loop basement membrane thickening due to subepithelial deposits of IgG and C3 and of Kappa and Lambda light chains, which may have a granular appearance due to immunofluo- rescence.,These deposits lead to an increase in glomerular tuft size. A study has shown that the glomerular area of patients with membra- nous glomerulopathy is significantly higher than that of patients with MCD.Another study showed that glomeruli of membranous glome- rulonephritis were significantly larger than glo- meruli of FSGS.The results obtained in the present study are in agreement with the litera- ture. Moreover, disease groups that progress with immune deposits which include lupus nephritis, Berger's disease, and ADGN gene- rally exhibit an increase of glomerular tuft area,,,which also was found in this study although the results did not differ significantly.
The median of Bowman's space area was higher in the control group than podocytopathy (FSGS/MCD) and thin basement membrane/ Alport syndrome groups. Glomeruli are gene- rally smaller in MCD in comparison with other renal diseases.,In our evaluations, Bowman's capsule, the glomerular tuft, and Bowman's space were shown to be reduced in podocyto- pathy group (FSGS/MCD), that is, the glome- rulus was overall smaller. As MCD is the main cause of Nephrotic syndrome in children,,the majority of the cases that remain with a differential diagnosis of FSGS and MCD were possibly MCD.
The thin membrane disease/Alport syndrome group also had small glomerulus. In the early stages, Alport syndrome is characterized by discrete changes such as mild hypercellularity and mesangial expansion, thickening and wrin- kling of glomerular capillary loops in a focal fashion, persistence of some fetal glomeruli into adulthood, and reduced glomerular tuft area.,These characteristics explain a reduction in the size of the glomeruli including the reduction of Bowman's space.
According to some studies, the parietal epithelial cells may play an important role in the pathogenesis of some kidney diseases. In FSGS, these cells may become focally activated and invade the glomerular tuft via an adhesion in response to primary lesions. At this location, they displace podocytes, induce the matrix deposition and lead to mesangial fibrosis of the affected segment.These changes in parietal epithelial cells could reduce Bowman's space. Another study showed that vascular injury and GBM disruption could lead to the release of plasma which in turn induces proliferation of parietal cells and their loss of polarity. As a result, cellular and fibrocellular crescents could be formed even in noninflammatory chronic glomerulopathies such as Alport syndrome.Furthermore, although glomeruli are usually preserved by light microscopy in the podo- cytopathy (FSGS/MCD), and in the thin base- ment membrane/Alport syndrome groups, the lesions observed in each glomerulopathy, even if mild, can lead to reduction in Bowman's space in comparison to subjects without kidney disease. This may be a possible explanation as to why Bowman's space is larger in the control group than in the other groups.
There was a positive and significant correla- tion between Bowman's capsule area and the levels of proteinuria, creatinine, and urea, as well as between the glomerular tuft area and the levels of proteinuria, creatinine, and urea of the patients, regardless of their nephropathy. It is well established that glomerular changes, parti- cularly those in the glomerular filtration barrier, are closely associated with the development of proteinuria as a target factor in the pathogenesis of Nephrotic syndrome.Moreover, in a study in which individuals between seven and 19 years who were born with low birth weight and developed proteinuria at school age, the renal biopsy showed an increase in glomerular size when compared with a control group, sugges- ting an association between proteinuria and glomerular hypertrophy.In clinical practice, urea and creatinine are considered to be mar- kers of renal glomerular function.Maximal glomerular diameter were significantly related to an increase in serum creatinine value accor- ding to a study of patients with IgA nephro- pathy.The correlations observed in this study indicate that the larger the glomerular tuft area and Bowman's capsule area, the lower is the renal function as demonstrated by the progres- sive increase in proteinuria and serum urea and creatinine.
One of the limitations of this study is that only a few biopsies of patients between 0 and 18 years old are sent for this service. Because of this, relatively only a low number of patients could be included in this study. Another limi- tation of this study is that it was not possible to assess the evolution of the different patient's renal diseases, which would contribute to a bet- ter understanding of the nephropathies. Further- more, many kidney biopsies are sent to the pathologist without adequate information regar- ding medications of patients, clinical and labo- ratory data, which hinders a complete and appropriate diagnosis. These limitations indi- cate the need for greater interaction between clinicians and pathologists.However, we be- lieve that this study can provide relevant infor- mation about morphology features of glome- rulopathies in pediatric patients and its asso- ciation with renal function.
Glomerular morphometry may contribute to the diagnosis of some glomerulopathies, since in the present study, membranous glomerulo- pathy showed an increase in the mean glome- rular tuft area and patients with podocytopathy presented a reduction of their glomeruli. Fur- thermore, the association between glomerular morphometric parameters and laboratorial data can potentially promote a better understanding of the pathogenesis of kidney diseases, espe- cially in pediatric patients in whom studies are less frequent.
This study was conducted at Nephropathology Service in General Pathology Division of Triangulo Mineiro Federal University, Uberaba, Minas Gerais, Brazil, with grants from Conselho Nacional de Desenvolvimento Científico e TecnolÓgico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de nνvel Superior (CAPES), Fundação de Amparo ΰ pesquisa do Estado de Minas Gerais (FAPEMIG), and Fundação de Ensino e Pesquisa de Uberaba (FUNEPU).
Conflict of Interest
All authors declare that they had no potential conflicts of interest relevant to this article.
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Rosana Rosa Miranda Corrêa
Division of General Pathology, Biological and Natural Sciences Institute, Federal University of Triângulo Mineiro, Rua Frei Paulino, 30. CEP 38025-180, Uberaba-Minas Gerais
[Figure 1], [Figure 2]