European Journal of Cardiovascular Medicine

As healthcare services improve worldwide, people tend to live longer and become healthier. Studies reveal that approximately 11% of the world’s population is older than 60 years. This proportion is expected to increase 22% by 2050. India is the second most populated country in the world, with adults aged over 60 years comprising approximately 10–13% of the total population. Nevertheless, the clinical progression and morphological features of these diseases are affected by aging. [1-3] Nephrotic syndrome (NS) is characterised by massive proteinuria, hypalbuminaemia, and oedema, and is a common syndrome seen in nephrology practice, both in adults and children. In clinical practice, NS is the leading cause of oedema due to renal disease.

In paediatric patients, the approach to nephrotic syndrome is empirical steroid therapy based on the presumption of minimal change Nephrotic Syndrome as the usual cause. In children, renal biopsy is indicated only if atypical features are encountered in less than 10% of patients. Renal biopsy continues to play an essential role in the clinical assessment of haematuria, proteinuria, and kidney failure. This is an acceptable practice considering the difficulty of performing renal biopsy which may necessitate general anaesthesia. The clinical scenario of adult patients is entirely different. Here, only a minority of patients showed minimal changes in the disease. Even in this group, the clinical response to empirical steroid therapy is unpredictable and often requires as long as four months for remission. In addition, morbidity associated with empirical steroid therapy is substantial, especially in the elderly. In contrast, renal biopsy is very easy in adults and has become virtually problem-free after the advent of the automated tumour biopsy gun based on the Wim Silverman needle principle. However, there is a substantial group of patients and physicians who avoid performing renal biopsy while waiting for a response to empirical steroid therapy. This may be justifiable in the adolescent age group which still behaves to a certain extent, as in paediatric patients. The only possible argument for such an approach among adult patients is based on logical prediction of the histological diagnosis. There are salient features in the clinical data of the patient which can often guide the clinician to predict the histological type of nephrotic syndrome without performing a renal biopsy. The use of epidemiological, clinical, and laboratory features can enable an empirical histological prediction when applied judiciously to an individual scenario. We conducted a prospective study to examine the potential of this design. Individual data were utilised to predict the histological type and then correlated with the actual status after renal biopsy.

Previous research indicated that MGN (membranous glomerulonephritis) was the primary cause of nephrotic syndrome in adults in both Europe, and the United States.[4] Recent research has revealed that FSGS (focal segmental glomerulosclerosis) is significantly increasing and has become the most prevalent glomerular disease among Hispanic and African-American populations.[4,5] Certain research conducted in India has demonstrated a decrease in the MPGN (mesangiocapillary glomerulonephritis) incidence and an increase in the incidence of focal segmental glomerulosclerosis, however, other studies have not supported this pattern.[6,7] The present study aimed to investigate the clinicopathological spectrum of NS in adult patients.

Study design and population

This cross-sectional study was conducted at the Bangalore Medical College and Research Institute, Karnataka, India, after obtaining approval from the Institutional Ethics Committee. We included 39 adult patients with NS, based on the inclusion and exclusion criteria. Patients willing to give written informed consent with above 18 years of either sex with nephrotic range proteinuria of >3.5 g/1.73 m² body surface area/day or >50 mg/kg/day undergoing renal biopsy from September 2018 to May 2020 were included. Patients with coagulopathies, contracted kidneys, solitary kidneys, acute pyelonephritis, history of vesicoureteral reflex, long-standing diabetes mellitus, and those who gave negative consent for renal biopsy were excluded from the study.

Demographic details of the patients with respect to age, sex, presenting symptoms, and blood pressure (BP) were recorded. Serum urea, creatinine, thyroid-stimulating hormone (TSH), and total cholesterol were analysed in the blood samples of all patients. Further investigations, including anti-double-stranded deoxyribonucleic acid tests, blood sugar levels, anti-neutrophil cytoplasmic antibody tests, and complement levels, were carried out as deemed necessary.

At the time of presentation, none of the patients had fever or any other indication of infectious disease. Individuals who had previously undergone an evaluation for nephrotic-range proteinuria due to a similar illness were excluded from the study. Furthermore, none of the patients included in our study was diagnosed with diabetes.

Procedure for renal biopsy

All patients underwent ultrasound examination of their kidneys, which was followed by renal biopsy after obtaining informed consent. Biopsy was conducted under the guidance of ultrasound and local anaesthesia using a 14 G Bard Trucut biopsy gun. The individuals underwent monitoring for 24 hours to identify procedure-related issues. Immunofluorescence (IF), histopathological (HP), and electron microscopic (EM) examinations were performed on the biopsy material. All slides for histopathological examination were analysed after they were stained with H and E and periodic acid-Schiff. Masson's trichrome staining and Jones silver staining were performed in selected patients

An immunofluorescence examination was conducted using fluorescein isothiocyanate-conjugated antibodies against immunoglobulin A. This was followed by electron microscope examination using Epon embedding, with sections at 65-70 nm uranyl acetate-lead acetate staining, and Ziess 906 visualisation. Based on renal biopsy and clinical findings, subjects were grouped into categories corresponding to the histopathological types of glomerular diseases.

Statistical method

The data were entered into Microsoft Excel and descriptive statistics were used. Using Statistical Package for Social sciences version 20.0, (SPSS, IBM, USA) the data was analysed.

Age groups

In our study population, the female population were 38.5% (n=15) and males was 61.5% (n=24). All patients were between 18 and 64 years of age, with an average age of onset of 32.64 years. Among the patients, 53.8% (n=21) were between 18-30 years of age, 23.1% (n=9) were in 31-40 years age group, 12.8% (n=5) were in 41-50 years age group, 7.7% (n=3) were in 51-60 years age group, and 2.6% (n=1) were aged > 60 years. Among the female patients, 46.7% (n=7) were in the 18-30 years age group, whereas among the male patients, 58.3% (n=14) were in the 18-30 years age group. (Table 1)

Presenting complaints

We found that pedal oedema was the most commonly reported symptom in 87% (n=34) of the patients, followed by facial puffiness in 64.1% (n=25), and frothy urine in 46.2% (n=18). A total of 33.3% (n=13) of patients presented with all these 3 combinations of symptoms. (Table 1)

Systemic hypertension

On examination, 76.9% of patients (n=30) had systemic hypertension. Among these patients, 23.1% (n=9) had stage 1 hypertension and 53.8% (n=21) had stage 2 hypertension. Among patients with systemic hypertension, 40% (n=12) were females and 60% (n=18) were males. Among the males, 20.8% (n=5) had stage 1 hypertension and 54.2% (n=13) had stage 2 hypertension. Among the females, 26.7% (n=4) had stage 1 hypertension, and 53.3% (n=8) had stage 2 hypertension. (Table 2) Systemic hypertension was present in 100% (n=5) of patients with FSGS (focal segmental glomerulosclerosis) patients, 87.5% (n=7) of IgA nephropathy patients, and 86.67% (n=13) of patients with membrane glomerulonephritis (MGN) patients. The lowest prevalence was observed in mesangiocapillary glomerulonephritis (MCGN) in 37.5% (n=3) of patients.

Severity of proteinuria

Urine protein over a 24-hour period varied from 3g/day to 12.3g/day. The mean value were 6.52g/day. Proteinuria levels ranged from to 3-6 g/day in 48.7% (n=19) of patients, 6.1 - 9 g/day in 38.5% (n=15) of patients, 9.1- 12 g/day in 10% (n=4) of patients, and > 12 g/day in only 1 patient (2.56%). Among the different histological types, the highest mean proteinuria level was observed in FSGS, with an average of 8.16 g/day. (Table 2)

Hypercholesterolaemia

Hyperlipidaemia was observed in most patients. Approximately 46.2% (n=18) of the subjects had cholesterol levels > 300 mg/dL. All eight patients with MCGN were identified to have hypercholesterolaemia >300 mg %, followed by 40% (n=6) of patients with MGN. The highest cholesterol level was observed in the MCGN group, with a mean of 409.87 mg/dL. Serum cholesterol levels varied among histopathological types. (Table 3)

Serum creatinine

Urea and creatinine levels were increased in 25.6% (n=10) of the patients. Elevated serum creatinine levels were observed in 80% (n=4) of the patients diagnosed with FSGS and in 50% (n=4) of the subjects with IgA nephropathy. In contrast, patients with MCD (minimal change disease) and MGN had normal serum creatinine levels (Table 6.2). The highest serum creatinine levels were recorded in patients with FSGS, with an average of 1.88 mg/dL. (Table 3)

Thyroid profile

Hypothyroidism was present in 69.2% (n=27) of the patients. The hypothyroidism prevalence was 73.3% (n=11) in membranous nephropathy, 62.5% (n=5) in IgA nephropathy, 75% (n=6) in MCGN, and 80% (n=4) in FSGS. The most severe cases of hypothyroidism were observed in FSGS, with a mean serum TSH level of 6.7 micro units/ml. (Table 3)

Histopathology findings on renal biopsy

All the patients underwent renal biopsy. In adults membranous nephropathy was the primary cause of nephrotic syndrome, accounting for 38.5% (n=15) of patients with a male (n=9): female (n=6) ratio of 1.5:1. IgA nephropathy was found in 20.5% (n=8) of the subjects, with a male (n=6): female (n=2) ratio of 3:1. MCD was responsible for nephrotic syndrome in 20.5% (n=8) of subjects with a male (n=5): female (n=3) ratio of 1.67:1. FSGS was present in 12.8% (n=5) of the subjects, with a male (n=2): female (n=3) ratio of 2:3. A notable number of patients had biopsy findings categorised as 'others', which included 1 case of C3 mediated glomerulonephritis and 1 case of lupus nephritis. (Table 3)

TABLES

Table 1: Distribution of patients based on age, sex, age groups and incidence of symptoms observed

Table 2: Hypertension observed among sex, hypertension, proteinuria observed among histopathology types on renal biopsy findings

   *C3 mediated glomerulonephritis, Lupus nephritis

Table 3: Total cholesterol, serum creatinine and serum TSH among histopathology types on renal biopsy findings

*C3 Mediated glomerulonephritis, Lupus Nephritis

Table 4: Comparison of glomerular lesions among nephrotic syndrome in adults in different Indian studies

MGN: membranous glomerulonephritis, FSGS: Focal segmental glomerulosclerosis, MCGN: mesangiocapillary glomerulonephritis, IgA: immunoglobulin A nephropathy, MesPGN: mesangial proliferative glomerulonephritis, MPGN: mesangiocapillary glomerulonephritis. The figures in parentheses are the percentages.

Nephrotic syndrome is known to be accompanied by severe proteinuria, peripheral oedema, hypoalbuminemia, and hypercholesterolaemia. Our study examined the clinical features and biopsy results of the 39 patients. Of these, 24 (61.5%) were male and 15 (38.5%) were female. Similarly in a study by Yousuf et al et al. 67% patients were male while 33% were females.[8] The highest number of male and female patients was observed in the third decade of life. Most patients (87 %) had facial pedal oedema as the presenting symptom.

Systemic hypertension was observed in all patients (n=5, 100%) diagnosed with FSGS. An average proteinuria of 8.16 g/day was predominantly observed in FSGS, indicating the highest mean proteinuria among the studied patients. Most patients exhibited hyperlipidaemia, with approximately 46.2% (n=18) being affected. The highest levels of cholesterol were detected in the MCGN group, with a mean of 409.87 mg/dL. The mean proteinuria was 6.52 ± 2.08 g/24hr and mean serum urea was 39.12 ± 19.6 mg/dl. Dyslipidaemia was observed in 66% patients.

In our study population, hypertension and renal insufficiency were present in 76.9% and 25.6% of the patients, respectively. Higher levels of serum creatinine were present in 80% of patients diagnosed with FSGS (n=4) and in 50% of patients with IgA nephropathy (n=4). Hypothyroidism was present in most of the patients (69.2%). The most severe hypothyroidism was noted in subjects diagnosed with FSGS, with a mean serum TSH level of 6.7 micro units/ml. Therefore, we examined the aetiology of nephrotic syndrome and discovered that membranous nephropathy was identified in 38.5% (n=15) of the patients, followed by IgA nephropathy in 20.5% (n=8) of the patients, and 20.5% (n=8) of the patients. Additionally, our study documented 1 case of lupus nephritis and 1 case of C3 mediated glomerulonephritis. Various studies conducted in different locations have shown evolving patterns in the aetiology of nephrotic syndrome in adults.

Glomerular disease is a significant contributor to the development of ESRD (end-stage renal disease). The histological spectrum of glomerular disease is different in adults than that in children. Overall, membranous glomerulonephritis was the leading cause of nephrotic, followed by MCGN and IgA nephropathy. The most common primary glomerular diseases causing nephrotic syndrome in children and adults are minimal change diseases and membranous glomerulonephritis, respectively.[9] Recently it has been found that Focal segmental glomerulosclerosis is most common cause of primary nephrotic syndrome in children and adult.[10] Control of proteinuria is therefore essential to prevent the progression of renal diseases to chronic renal failure.[11] Nephrotic syndrome is primarily caused by minimal change disease, with oedema being the most common presenting sign.

In contrast to the findings of Yousuf et al., our study revealed a higher incidence of MGN, accounting for 38.5% of cases, as opposed to their 22% frequency. However, both studies found nephrotic syndrome to be caused by a spectrum of glomerular diseases. In with that FSGS Yousuf et al. observed a frequency of 54%, and in our study, it was 12.8%, shown 4 a fold increase in frequency. IgA levels remained the same in both the study by Yousuf et al. and our study. IgA nephropathy in Yousuf et al. accounted for 10.6% patients and in our study it was 20.5% as cause of nephrotic syndrome.[8]

The reasons for the changing spectrum are manifold. This could be due to an improvement in quality of life, a decline in the infection rate, an increase in obesity rates, better socioeconomic conditions, and changes in the indications for renal biopsy. The extensive utilisation of IF and EM in examining renal biopsies has led to an increased diagnosis of MGN, MCGN, and IgA nephropathy.

Table 4 provides a summary of additional research conducted in India on this topic. Although earlier studies found FSGF to be commonest cause of NS, our study showed that membranous glomerulonephritis is commonest aetiology of NS. Research conducted in Delhi and Rohtak uncovered evidence implicating minimal change disease as the cause of more than one-third of NS cases.[12,13] In a study conducted by Golay et al. in Kolkata, it was discovered that FSGS was the most prevalent disease, accounting for 27.4% of the patients, while MGN was the third most common, accounting for roughly 25%.14 The figure presented does not resemble our current data, where FSGS was responsible for only 12.8% and MGS for 38% of the patients. However, they found MGN in 25% of patients, making it the second commonest cause of NS whereas MPGN was observed only in 7% of patients. This contrasts with our data, where MGN was observed in approximately 38% of the patients, while MPGN was observed in approximately 2.6% of the patients. However, the exact cause of this disparity remains ambiguous. Both Agarwal et al. showed data similar to those of our study, showing MGN as the most common cause. [12,13] A study conducted by Siegel et al revealed that electron microscopy plays a crucial role in accurately diagnosing 11% of patients.[14] The incidence of IgA was 10.6% in our study which is comparable to the 4-20% in other studies from India.

MGN is the commonest cause of nephrotic syndrome, accounting for 38.5% of primary glomerular diseases. This was followed by MCGN and IgA in 20.5% of patients. FSGS constituted 12.8%, and MPGN 2.6%. A major limitation of the current study was the relatively small sample size. Additionally, as our institution primarily serves the South Indian population, our findings may not be generalisable to other regions of the nation.

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