Nephrotic syndrome in the elderly: epidemiological aspects, clinical data, and renal biopsy findings

Nephrotic syndrome is the most common clinical presentation of glomerular disease in elderly patients, and renal biopsy is an important diagnostic resource. The aim of this study was to describe nephrotic syndrome among elderly patients in Brazil, focusing on tubulointerstitial and vascular involvement. This was a retrospective study of patients over 65 years of age with nephrotic syndrome who underwent renal biopsy between January 2012 and December 2019. Of the 123 renal biopsies that occurred during the study period, 44 (35.8%) were performed for the investigation of nephrotic syndrome. Among those 44 cases, the main etiologies were membranous nephropathy in 13 cases (29.5%), amyloidosis in ten (22.7%), non-collapsing focal segmental glomerulosclerosis (FSGS) in four (9.1%), and collapsing FSGS in four (9.1%). Patients with minimal change disease (MCD) had the lowest degree of interstitial fibrosis compared with the other glomerulopathies, and histological signs of acute tubular necrosis (ATN) were less common among those with amyloidosis than among those with membranous nephropathy, FSGS, or MCD (P=0.0077). Of the patients with ATN, the frequency of acute kidney injury (AKI) was highest in those with MCD (P<0.001). All patients had some degree of vascular involvement, regardless of the type of glomerulopathy. In conclusion, the second most common cause of nephrotic syndrome in this population was amyloidosis, and acute interstitial tubule involvement was more marked in MCD. Vascular involvement is something that cannot be dissociated from the age of the patient and is not only due to the underlying glomerulopathy.

Lupus nephritis is more severe in children and adolescents than in older adults

OBJECTIVE

To evaluate clinicopathological features and treatment response in patients with lupus nephritis (LN), comparing the childhood- and late-onset forms of the disease.

METHODS

We retrospectively analyzed clinical presentation, treatment and evolution in patients diagnosed with LN by renal biopsy between 1999 and 2008. Patients were grouped by age-≤18 years (n = 23); and ≥50 years (n = 13)-and were followed for the first year of treatment.

RESULTS

The baseline features of the childhood- and late-onset groups, respectively, were as follows: mean age, 15 ± 2 and 54 ± 5 years; female gender, 87% and 92%; hypertension, 87% and 77%; Systemic Lupus Erythematosus Disease Activity Index, 29 ± 9 and 17 ± 7 (p = 0.002); estimated glomerular filtration rate (eGFR), 86 ± 66 and 70 ± 18 ml/min; concurrent SLE/LN diagnosis, 90% and 15% (p < 0.001); crescents on biopsy, 74% and 30% (p = 0.02); activity index on biopsy, 4.8 ± 2.6 and 3.3 ± 1.9 (p = 0.10); and interstitial fibrosis (>10%), 39% and 61% (p = 0.08). Treatment consisted mainly of methylprednisolone, prednisone and intravenous cyclophosphamide, average cumulative doses being similar between the groups. After 12 months of treatment, the eGFR in the younger and older patients was 116 ± 62 and 78 ± 20 ml/min, respectively (p = 0.005). Three of the younger patients progressed to dialysis at 12 months, compared with none of the older patients.

CONCLUSION

Childhood-onset LN seems to be more severe than is late-onset LN.

Worse renal outcome of lupus nephritis in male patients: a case–control study

Background: Progression and long-term renal outcome of lupus nephritis (LN) in male patients is a controversial subject in the literature. The aim of this study was to evaluate the influence of male gender on the renal outcome of LN.

Methods: All male (M) LN patients who fulfilled American College of Rheumatology lupus criteria and who were referred for a kidney biopsy from 1999 to 2009 were enrolled in the study. Subjects with end-stage renal disease at baseline, or follow-up time below 6 months, were excluded. Cases were randomly matched to female (F) patients according to the class of LN, baseline estimated glomerular filtration rate (eGFR, Modification of Diet in Renal Disease simplified formula) and follow-up time. Treatment was decided by the clinical staff based on usual literature protocols. The primary endpoint was doubling of serum creatinine and/or end-stage renal disease. The secondary endpoint was defined as a variation of glomerular filtration rate (GFR) per year (ΔGFR/y index), calculated as the difference between final and initial eGFR adjusted by follow-up time for each patient.

Results: We included 93 patients (31 M : 62 F). At baseline, M and F patients were not statistically different regarding WHO LN class (II 9.7%, IV 71%, V 19.3%), eGFR (M 62.4 ± 36.4 ml/min/1.73  m2 versus F 59.9 ± 32.7 ml/min/1.73 m2), follow-up time (M 44.2 ± 27.3 months versus F 39.9 ± 27.9 months), and 24-hour proteinuria (M 5.3 ± 4.6 g/day versus F 5.2 ± 3.0 g/day), as well as age, albumin, C3, antinuclear antibody, anti-DNA antibody and haematuria. There was no difference in the primary outcome (M 19% versus F 13%, log-rank p = 0.62). However, male gender was significantly associated with a worse renal function progression, as measured by ΔGFR/y index (β coefficient for male gender −12.4, 95% confidence interval −22.8 to −2.1, p = 0.02). The multivariate linear regression model showed that male gender remained statistically associated with a worse renal outcome even after adjustment for eGFR, proteinuria, albumin and C3 complement at baseline.

Conclusion: In our study, male gender presented a worse evolution of LN (measured by an under GFR recovering) when compared with female patients with similar baseline features and treatment. Factors that influence the progression of LN in men and sex-specific treatment protocols should be further addressed in new studies.

Collapsing glomerulopathy associated with proliferative lupus nephritis: reversible acute kidney injury

Collapsing glomerulopathy is a rare form of glomerular injury, characterized by segmental or global collapse of the glomerular capillaries, wrinkling and retraction of the glomerular basement membrane, and marked hypertrophy and hyperplasia of podocytes. Prognosis is usually poor, with most cases developing end-stage renal disease, in spite of treatment. The association of collapsing glomerulopathy and systemic lupus erythematosus is very unusual. In this report, we describe the first case of a simultaneous diagnosis of collapsing glomerulopathy and diffuse proliferative lupus nephritis. The case presented with acute kidney injury and nephrotic syndrome and evolved with partial remission of nephrotic syndrome and recovery of renal function after aggressive treatment with intravenous cyclophosphamide and methylprednisolone.

Decreased in vitro osteoblast proliferation and low turnover bone disease in nonuremic proteinuric patients

Patients with proteinuria, even those with normal glomerular filtration rate, often present abnormal bone histology. We evaluated bone histology and the in vitro proliferation of osteoblasts in samples obtained from 17 proteinuric patients with primary glomerulopathies. Histomorphometric analysis of bone biopsies was performed, and bone fragments were obtained for osteoblast culture, in which we evaluated cell proliferation. In comparison to controls, patients presented lower trabecular bone volume (20.9+/-14.5% vs 26.8+/-5.9%; P=0.0008); lower trabecular number (1.7+/-0.2/mm vs 2.0+/-0.3/mm; P=0.004); and greater trabecular separation (475.5+/-96.4 microm vs 368.3+/-86.2 microm, P=0.0002). We also found alterations in bone formation and resorption: lower osteoid volume (0.9+/-0.7% vs 2.0+/-1.4%; P=0.0022); lower osteoid thickness (6.4+/-2.8 microm vs 11.5+/-3.2 microm; P<0.0001); less mineralizing surface (4.6+/-3.1% vs 13.5+/-6.0%; P<0.0001); lower bone formation rate (0.03+/-0.04 microm(3)/microm(2)/day vs 0.09+/-0.05 microm(3)/microm(2)/day; P<0.0001); and greater osteoclast surface (0.35+/-0.6 vs 0.05+/-0.1%, P=0.0016). Mean in vitro osteoblast proliferation was lower in patients than in controls (910.2+/-437.1 vs 2261.0+/-1121.0 d.p.m./well, P=0.0016). Serum concentrations of 25-hydroxyvitamin-D(3) correlated negatively with proteinuria and positively with in vitro osteoblast proliferation. Our results demonstrate that nonuremic proteinuric glomerulonephritic patients present bone structure disorder, low bone formation and high bone resorption, as well as low osteoblast proliferation.

Comparative study of IgA nephropathy with and without crescents

Glomerular crescents were analyzed as a prognostic factor in retrospectively reviewed data from 144 patients with biopsy-proven IgA nephropathy. Crescents were found in 26 (18%) patients, and detected in 2 to 100% of glomeruli in each specimen. In 5% of the patients more than 50% of the glomeruli were affected. Thirty patients with IgA nephropathy without crescents were studied as a control group. Mean age was 30.3 +/- 9.4 and 30.2 +/- 12.0 years for the patients with and without crescents, respectively, and males prevailed in both groups. The length of follow-up was 23.2 +/- 41.6 months for patients with crescents and 29.3 +/- 35.3 months for patients without crescents. Eighty percent of the patients with crescents were hypertensive, compared to 27% of the non-crescent control group (P < 0.05). Mean serum creatinine at the time of diagnosis was 3.9 +/- 2.9 and 1.9 +/- 2.1 mg/dl for the patients with and without crescents, respectively. Initial urinary protein excretion was higher in patients with crescents (4.6 +/- 3.5 vs 1.2 +/- 0.9 g/day; P < 0.05). At the end of follow-up 17 patients (77.3%) from the crescent group and 3 (11.1%) from the non-crescent group had end-stage renal disease (P < 0.0001). The presence of crescents was associated with higher levels of initial serum creatinine and urinary protein excretion, and a higher frequency of hypertension and progression to end-stage renal disease.

Glycosuria in glomerular diseases: histopathology and clinical correlations

There are doubts about the presence of glycosuria and the progress of glomerular disease. Some reports suggest that glycosuria could be an index of a more severe tubulointerstitial lesion. We investigated the presence of glycosuria in 60 patients with primary glomerular diseases: 17 patients (28%) had glycosuria and 43 patients (72%) were glycosuria free. The two groups were similar in age, arterial pressure and sex. Serum creatinine was higher in patients with glycosuria (2.0 +/- 1.7 vs 1.3 +/- 0.9 mg/dl, P < 0.05). The protein excretion rate was 7.5 +/- 3.7 vs 5.3 +/- 4.2 g/day (P > 0.05) in patients with and without glycosuria, respectively, while serum albumin was lower in patients with glycosuria (1.7 +/- 0.6 vs 2.7 +/- 1.0 g/dl, P < 0.05). Several histological forms were present in the group with glycosuria, with membraneous glomerulonephritis being the most frequent. Histological evidence of tubular atrophy and interstitial fibrosis prevailed in patients with glycosuria, suggesting a poor prognosis for these patients. We may conclude that the presence of glycosuria in patients with glomerular disease is associated with more pronounced tubular atrophy and interstitial fibrosis and therefore imply a poorer prognosis.

Snakebite-induced acute renal failure: an experimental model

Acute renal failure (ARF) has been frequently reported after bites from the Viperidae snake family. The lack of a reproducible animal model has hampered the study of renal damage mechanisms. Intravenous injection of rats with 0.4 mg/kg of Bothrops jararaca venom produced functional and morphologic changes similar to those observed in human snakebite-induced ARF. There was an acute and significant decrease in the glomerular filtration rate, diuresis, and renal plasma flow. Serum fibrinogen levels decreased significantly. There was intravascular hemolysis, as shown by a significant decrease in hematocrit, and an increase in plasma lactate dehydrogenase levels and free hemoglobin. Blood pressure and serum creatine phosphokinase levels were not affected. Light and electron microscopy showed massive fibrin deposition in glomerular capillaries, proximal and distal tubular necrosis, and hemolyzed red blood cell casts in renal tubules. Based on these findings, a model of snakebite-induced ARF was achieved. Ischemia related to glomerular coagulation and intravascular hemolysis were the most important pathogenic factors causing a decrease in the glomerular filtration rate, although a direct venom nephrotoxicity cannot be excluded.

Bicarbonate reabsorption and electrophysiology of proximal tubules in uninephrectomized rats

1. The kinetics of acidification of luminal fluid in hypertrophied proximal tubules after unilateral nephrectomy was studied by stationary microperfusion and continuous measurement of luminal pH with antimony microelectrodes. 2. Trans-epithelial and basolateral membrane electrical potential differences were measured in order to detect modifications in electrogenic transport mechanisms under these conditions. 3. The values of stationary pH and HCO3- concentration were significantly lower, the mean acidification half-time was not different and net reabsorptive HCO3- fluxes in proximal tubules were significantly increased in uninephrectomized rats. According to an electrical analogue model, these results suggest (a) a reduction in the internal series resistance of the H+ pump, caused perhaps by an increased density of pump sites, and (b) an increase in the protonmotive force of the pump. 4. The trans-epithelial electrical potential difference measured in free flow conditions was significantly more lumen-positive in uninephrectomized rats. The trans-epithelial electrical potential difference measured during intraluminal perfusion with Ringer solution containing 30 mmol/l HCO3- was significantly more negative in all groups studied. In uninephrectomized rats treated with acetazolamide, the trans-epithelial electrical potential difference was more lumen-negative than that in untreated uninephrectomized rats. These results are compatible with a steeper transepithelial Cl- gradient as well as with electrogenic, active H+ secretion. 5. There was no significant difference in the basolateral electrical potential difference between control and uninephrectomized rats. 6. In conclusion, our data show an increase in the transport rates of HCO3- in the proximal tubule of uninephrectomized rats, which may be due to an increase in the density of transporters in the brush-border membrane, and an increased ability of the transport mechanism to create H+ gradients.