Pathophysiology of edema formation in children with nephrotic syndrome not due to minimal change disease

It has been shown that children with nephrotic syndrome due to minimal change disease (MCD) can present with avid salt retention and stimulated vasoactive hormones, as well as with stable edema. The present study examines these conditions in children with nephrotic syndrome not due to MCD (non-MCD). In six children with hypovolemic symptoms (congenital nephrotic syndrome in four), strong sodium retention (fractional sodium excretion, FE(Na), 0.2 +/- 0.2%) was found. Lithium clearance (FE(Li)) and maximal water excretion (Vmax) were suppressed, suggesting avid sodium reabsorption throughout the nephron. Aldosterone, renin, and norepinephrine were elevated. Sixteen other children with non-MCD had stable edema. FE(Na) was 1.8 +/- 1.1%, whereas FE(Li), Vmax, and hormones were normal, and not different from data in 35 nonproteinuric children. In children with MCD, 12 presented with hypovolemic symptoms and strong sodium retention (FE(Na) 0.3 +/- 0.3%), whereas 15 were stable (FE(Na) 1.1 +/- 0.7%). Regarding tubular sodium handling and hormones, the same distinction could be made as for the children with non-MCD. However, hypoproteinemia differed. In the children with non-MCD lesions, plasma colloid osmotic pressure was significantly lower in the hypovolemic types (4.2 +/- 0.4 mmHg) than in those with stable edema (13.0 +/- 3.8 mmHg; P < 0.05); in MCD, no such difference existed (respectively, 8.1 +/- 3.0 and 9.9 +/- 2.2 mmHg). In summary, children with nephrotic syndrome may present with pathophysiologic pictures of decreased effective circulating volume or of stable edema, regardless of whether they have non-MCD or MCD. The pathogenesis of the hypovolemic picture seems to be different, since it is associated with extreme hypoproteinemia only in the children with non-MCD.

Coadministration of albumin and furosemide in patients with the nephrotic syndrome

BACKGROUND

In patients with nephrotic syndrome, the natriuretic effect of furosemide (FU) is diminished. The effect of coadministration of FU and human albumin (HA) has remained controversial.

METHODS

In a double-blind, placebo-controlled study, nine nephrotic patients (six males, 48 +/- 4 years) on standardized sodium chloride intake, in random order on three separate days, received by intravenous administration for 60 minutes either (a) 60 mg FU plus a sham infusion, (b) 60 mg FU plus 200 ml of a 20% solution of HA, or (c) sham infusion plus 200 ml of a 20% solution of HA. Urinary volume, sodium, albumin and FU excretion, renal hemodynamics, and plasma atrial natriuretic factor concentration were assessed.

RESULTS

Administration of FU alone significantly (P < 0.01) increased mean cumulative urinary sodium (259 +/- 30 mmol) and volume excretion (2684 +/- 167 ml) in the first eight hours as compared with the HA infusion alone (118 +/- 12 mmol, 1827 +/- 141 ml). The coadministration of FU and HA caused an even more marked increase (P < 0.01 vs. HA alone) of urinary sodium (312 +/- 28 mmol) and volume excretion (3230 +/- 201 ml); the difference to FU administration alone was significant (P < 0.05). Plasma atrial natriuretic factor, serum albumin concentration, and urinary albumin excretion increased significantly on both HA infusion days, whereas urinary excretion of FU remained unchanged with HA coadministration. Glomerular filtration rate (CIn) was not significantly affected by any of the infusion protocols, but effective renal plasma flow (CPAH) increased significantly on both HA infusion days.

CONCLUSIONS

Coadministration of HA potentiates the action of FU in patients with the nephrotic syndrome, but only modestly. This effect is mediated by changes in renal hemodynamics.

Nephrotic syndrome as a clinical manifestation of graft-versus-host disease (GVHD) in a marrow transplant recipient after cyclosporine withdrawal

GVHD is one of the most frequent complications of BMT and recently nephrotic syndrome (NS) has been described as a manifestation of chronic GVHD. Here, we present an AA patient who developed NS 1 year after BMT when cyclosporine was stopped. Renal biopsy showed focal sclerosis associated with membranous deposits. He also had other clinical manifestations of chronic GVHD: sicca-like syndrome and colestasis. After 15 days of CsA therapy, he experienced a remarkable improvement in the NS and GVHD as a whole. We comment on immunological mechanisms that could be involved in the pathogenesis of this manifestation.

Acute haemodynamic and proteinuric effects of prednisolone in patients with a nephrotic syndrome

BACKGROUND

Administration of prednisolone causes an abrupt rise in proteinuria in patients with a nephrotic syndrome.

METHODS

To clarify the mechanisms responsible for this increase in proteinuria we have performed a placebo controlled study in 26 patients with a nephrotic syndrome. Systemic and renal haemodynamics and urinary protein excretion were measured after prednisolone and after placebo.

RESULTS

After i.v. administration of 125-150 mg prednisolone total proteinuria increased from 6.66+/-4.42 to 9.37+/-6.07 mg/min (P<0.001). By analysing the excretion of proteins with different charge and weight (albumin, transferrin, IgG, IgG4 and beta2-microglobulin) it became apparent that the increase of proteinuria was the result of a change in size selectivity rather than a change in glomerular charge selectivity or tubular protein reabsorption. Glomerular filtration rate rose from 83+/-34 ml to 95+/-43 ml/min (P<0.001) after 5 h, whereas effective renal plasma flow and endogenous creatinine clearance remained unchanged. As a result filtration fraction was increased, compatible with an increased glomerular pressure, which probably contributes to the size selectivity changes. Since corticosteroids affect both the renin-angiotensin system and renal prostaglandins, we have evaluated the effects of prednisolone on proteinuria after pretreatment with 3 months of the angiotensin-converting enzyme inhibitor lisinopril or after 2 weeks of the prostaglandin synthesis inhibitor indomethacin. Neither drug had any effect on prednisolone-induced increases of proteinuria.

CONCLUSIONS

Prednisolone increases proteinuria by changing the size selective barrier of the glomerular capillary. Neither the renin-angiotensin axis nor prostaglandins seem to be involved in these effects of prednisolone on proteinuria.

Influence of serum albumin on renal function in nephrotic syndrome

Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), determined by the clearances of inulin and para-aminohippuric acid, were evaluated in 119 children with different types of nephrotic syndrome and in different stages: the nephrotic stage (serum albumin < 25 g/l), recovery stage (25-35 g/l), and remission (> 35 g/l). GFR in the nephrotic stage was significantly lower than in remission and in controls, and was lowest at onset of the disease (84 +/- 6, 111 +/- 4, and 119 +/- 2 ml/min per 1.73 m2). ERPF was higher in the nephrotic stage than in recovery, especially in children with histological lesions. Thus the filtration fraction (FF) was greatly decreased in the nephrotic stage. In patients investigated both in the nephrotic and the remission phase, GFR and FF increased significantly. There was a direct correlation between the serum albumin concentration and FF and an inverse correlation between mean arterial pressure (MAP) and GFR and FF in all patients, a direct correlation between the serum albumin concentration and GFR in minimal change nephrotic syndrome patients, and an inverse correlation between ERPF and serum albumin in children with histological lesions. In conclusion, GFR and FF were decreased and ERPF increased in the nephrotic stage, normalizing in remission. The low GFR in the nephrotic stage was thus not dependent on hypoperfusion. We suggest that the low GFR is dependent on a very low ultrafiltration coefficient. The direct correlation between GFR and serum albumin and the indirect correlation between GFR and MAP suggest compensatory mechanisms that increase the ultrafiltration pressure to counteract the severely reduced ultrafiltration coefficient.

Quantitative morphometry of renal biopsies prior to cyclosporine in nephrotic syndrome

Use of cyclosporine (CsA) in the management of children with steroid-resistant (SRNS) and steroid-dependent (SDNS) nephrotic syndrome has become increasingly popular in recent years. Although most children receive a renal biopsy prior to initiation of CsA, the relationship between initial renal histology and the subsequent clinical response to CsA is not known. We analyzed the correlation between pre-CsA segmental and global glomerular scarring and interstitial fibrosis and the subsequent response to CsA in 23 children (5.6+/-1.0 years, Mean+/-SEM) with SDNS (n=8) and SRNS (n=15) treated with CsA for 24.2+/-3.8 months and followed for 28.0+/-4.1 months. Complete remission was obtained in 78% of patients within 67.6+/-16 days, while 18% had a partial response and 4% no response. Quantitative histological analysis revealed a trend toward partial rather than complete response with increasing segmental glomerular (P=0.13), global glomerular (P=0.05), and interstitial (P=0.08) scarring, and among patients with minimal change nephrotic syndrome versus IgM nephropathy versus focal segmental glomerulosclerosis. Among complete responders, linear regression analyses revealed no correlation between time to response and pre-CsA glomerular or interstitial scarring. We conclude that increased glomerular or interstitial scarring on a pre-CsA renal biopsy tends to correlate with a partial, rather than complete, response to CsA in childhood nephrotic syndrome.

Abnormal increase of creatine kinase plasma levels following muscle exercise in nephrotic patients

Nephrotic syndrome is a protein-wasting disorder affecting total body protein metabolism, often leading to reduction of lean body mass and changes of muscle cell composition. The aim of this study was to investigate the susceptibility to muscle cell damage in nephrotic patients following submaximal physical exercise, by detection of the creatine kinase (CK) plasma level changes. Fourteen patients affected by primary nephrotic syndrome, without chronic renal failure, underwent an exercise test on a cycle ergometer for 20 min at a constant speed (60 rpm). In each subject, the work rate (expressed as watts) was established as 70% of the maximum power theoretically calculated on a sex, age, weight and height basis. CK plasma levels (U/l) were determined before and 1, 3, 6 and 24 h after the exercise. Following exercise, CK plasma levels became higher in nephrotics than in normal controls. That is, the amount of CK increments was greater in nephrotics than in controls from the first hour after the end of exertion. These changes, both as absolute values and as percentage of the basal values, correlate positively to daily urinary protein losses; moreover, an inverse relationship was detected with albumin serum levels. However, no correlation was observed between the amount of plasma CK increases and age, body weight, plasma creatinine, plasma cholesterol or hemoglobin levels. These results demonstrate that a greater than normal increase of CK plasma levels occurs in nephrotics following physical exercise, and that this increment correlates with the severity of urinary protein wasting. This suggests an increased susceptibility to muscle injury in nephrotic patients probably related to protein depletion and/or to modifications of muscle cell metabolism. Further studies are needed to define the pathogenesis of our findings.

Peripheral microvascular parameters in the nephrotic syndrome

BACKGROUND

Peripheral edema, in combination with severe proteinuria and low serum albumin levels, is pathognomonic of the nephrotic syndrome, yet the exact mechanism of its formation is unknown. Two of the most important of the factors in Starling's forces controlling fluid filtration across the capillary have hitherto not been studied in nephrotic subjects.

METHODS

The hydrostatic capillary pressure at the finger nail-fold in actively nephrotic subjects and age and sex matched controls was studied, using direct puncture of the apex of the capillary under video microscopy, and a servonulling apparatus to give a direct measurement of capillary pressure. Capillary filtration capacity (CFC) at the calf was measured noninvasively by a modern derivative of the technique of mercury strain gauge plethysmography. Fifteen nephrotic subjects with a variety of underlying pathological lesions, and age matched controls were studied.

RESULTS

Contrary to the assumption of the "overflow" hypothesis of edema formation, there was no evidence of capillary hypertension. The capillary pressure showed no difference between nephrotic subjects and controls: median (range) of 17.6 (12.0 to 24.2) compared with 17.3 (9.0 to 21.6) mm Hg, P = NS. CFC was significantly higher in nephrotic subjects than controls [5.23 (3.28 to 8.52) x 10(-3) versus 3.55 (2.43 to 5.28) x 10(-3) ml/min/100 g/mm Hg, P < 0.01].

CONCLUSIONS

An increase in CFC provides a potentially novel mechanism contributing at least in part to the formation of peripheral edema in the nephrotic syndrome.

Impact of recurrent nephrotic syndrome after renal transplantation in young patients

Recurrent disease is a frequent complication of patients transplanted for steroid-resistant nephrotic syndrome associated with focal segmental glomerulosclerosis. Its long-term prognosis has rarely been studied. We examined 39 patients aged 4-25 (mean 13.5) years at the time of first transplantation (TX). Twelve of these (30%) developed nephrotic syndrome after the first TX and 2 of 8 after the second TX. The mean observation period from first TX to last observation with a functioning graft or graft loss was 5.4 (0.1-19.3) years. We confirmed that recurrent disease is associated with older age at onset of the primary disease, shorter time from onset to end-stage renal disease, and diffuse mesangial proliferation in the initial kidney biopsy. Remissions occurred in all 3 children undergoing early repeated plasma exchange and in 1 adolescent following introduction of cyclosporin A 7 years after TX. At last observation 42% of relapsing and 48% of non-relapsing patients with a similar follow-up period had a functioning first graft. Median first graft survival was almost identical in the relapsing and the non-relapsing patients (4.3 vs. 4.2 years). Histological lesions of focal glomerulosclerosis were detected in the posttransplant biopsies of only 3 patients. In conclusion, young patients with nephrotic syndrome associated with focal segmental sclerosis have a similar graft survival with and without recurrence of the nephrotic syndrome.

Mechanisms of progressive glomerular injury in membranous nephropathy

Glomerular function and structure were serially evaluated in 15 patients with membranous nephropathy who exhibited relapsing nephrosis and chronic depression of GFR. GFR declined from 56+/-8 (mean+/-SEM) at onset to 31+/-4 ml/min per 1.73 m2 after a 2- to 5-yr period of observation (P < 0.05). An analysis of filtration dynamics suggested persistent elevation of net ultrafiltration pressure. To examine a possible role for declining intrinsic glomerular filtration capacity as the basis for the observed hypofiltration, glomeruli in the baseline and a repeat biopsy (performed after a median of 28 mo) were subjected to morphometric analysis and mathematical modeling. Analysis of the baseline biopsy revealed a reduction in filtration slit frequency and thickening of the glomerular basement membrane, lowering computed hydraulic permeability by 66% compared with normal kidney donors. In contrast, filtration surface area was increased by 37% as a result of glomerular hypertrophy. The repeat biopsy revealed persistent depression of hydraulic permeability, primarily owing to foot process broadening. An additional finding was a decrease in filtration surface area from baseline in patent glomeruli, possibly due to encroachment on the capillary lumen of an increasingly widened basement membrane. Also, a striking increase in the prevalence of global glomerulosclerosis from 7+/-2% to 23+/-4% was found between the two biopsies, suggesting a significant loss of functioning nephrons. It is concluded that hypofiltration in membranous nephropathy is the consequence of a biphasic loss of glomerular ultrafiltration capacity, initially owing to impaired hydraulic permeability that is later exacerbated by a superimposed loss of functioning glomeruli and of filtration surface area.

Influence of age at onset on the outcome of steroid-sensitive nephrotic syndrome

To investigate whether age at onset of steroid-sensitive nephrotic syndrome (SSNS) is predictive of subsequent relapses, or influences outcome, we retrospectively studied 60 patients who were under 10 years of age at onset and were followed for over 10 years. They were divided into three groups according to age at diagnosis: group 1-3 (1.0-3.9 years at onset, n=24), group 4-6 (4.0-6.9 years at onset, n=22), and group 7-9 (7.0-9.9 years at onset, n=14). In the 51 patients with long-term remission, defined as remaining relapse-free over 3 years, the total number of relapses was significantly more in group 1-3 (n=18) than in group 4-6 (n=19), and the interval between onset and long-term remission was significantly longer. Group 4-6 and group 7-9 had fewer patients with active disease at 10 years, follow-up than group 1-3, as assessed by the Kaplan-Meier method. These data suggest that the age at onset of SSNS influences the clinical course (i.e., frequency of relapses) and the time to reach long-term remission. An age of less than 4 years at onset of SSNS is associated with greater likelihood for frequent relapses and a greater time interval to attain long-term remission.

[Nephrotic syndrome. What is new since the 1988 study?]

The authors make a retrospective review of 53 new cases of Nephrotic Syndrome followed up in the Nephrology Unit from November 1988 to March 1994, bearing in mind the evaluation of casual changes of the disease standard regarding a previous study of 1988. Epidemiological, clinical, therapeutical and evolutional aspects were studied. Forty-four cases of primary Nephrotic Syndrome (83%) were identified, 61.4% of which behaved as cortico-sensitive, 25% as cortico-dependent, and 13.6% as cortico-resistant; 8 cases (15%) of Nephrotic Syndrome secondary to infection, Systemic Lupus Erythematosus and Amyloidosis, and 1 case of congenital Nephrotic Syndrome (2%). The theory that the high number of cortico-dependent is, probably, related with a higher severity in the relapse diagnosis and/or changes in the children's standard of living is admissible. It was also observed that at present there is a lower number of hospital discharges, related to more careful attitudes adopted regarding the evolution of the disease.

[The restoration of cardiovascular system function in patients with chronic glomerulonephritis after the use in staged medical rehabilitation of measured therapeutic physical exercise]

As many as 195 patients were studied presenting with mixed, nephrotic, and hematuric varieties of chronic glomerulonephritis (ChG), aged 6-15 years, including 118 children from the test-groups who were given a combined therapy involving differentiated rest-and-movement regimens (DRMR) and graded therapeutical physical training (GTPT) and 77 controls who received none of the above treatments. The examination involved clinical as well as functional tests (the unit "Cardiocid"-aided ECG, EchoCG on the "Combison-420-5"), with the renal function being evaluated as recommended by Ota Shiuk. Commonly seen in those being admitted into hospital was nephrogenous hypertension as were abnormal changes in myocardium associated with automatism malfunction, inadequate conductivity, and impaired myocardial contractile ability. Clinical and functional tests as a whole suggested to us a latent cardiac insufficiency in those children presenting with faulty kidney function. Use of DRMR and GTPT in a complex of therapeutic and rehabilitative measures in a continuous staged medical rehabilitation project makes for improvement of the function of the cardiovascular system in all of the varieties of the condition particularly so in hematuric and nephrotic forms of ChG, as evidenced by ECG and EchoCG in a 5-yr follow-up.

Concentrating defect in experimental nephrotic syndrone: altered expression of aquaporins and thick ascending limb Na+ transporters

BACKGROUND

Several pathophysiological states associated with deranged water balance are associated with altered expression and/or intracellular distribution of aquaporin water channels. The possible role of dysregulation of thick ascending limb NaCl transporters, which are responsible for countercurrent multiplication in the kidney, has not been evaluated.

METHODS

Semiquantitative immunoblotting and immunocytochemistry were carried out in the kidneys of rat with adriamycin-induced nephrotic syndrome and in vehicle-injected control rats.

RESULTS

Preliminary studies confirmed the presence of a severe concentrating defect. Semiquantitative immunoblotting of outer medullary homogenates demonstrated a marked decrease in the abundance of three thick ascending limb Na+ transporters in nephrotic rats, namely the bumetanide-sensitive Na-K-2Cl cotransporter (BSC-1), the type 3 Na/H exchanger (NHE-3), and the alpha 1-subunit of the Na-K-ATPase. These results are predictive of a decrease in the NaCl transport capacity of the medullary thick ascending limb and therefore a decrease in countercurrent multiplication. Immunocytochemistry of outer medullary thin sections demonstrated broad (but highly variable) suppression of BSC-1 expression in the outer medullas of adriamycin-nephrotic rats. There was also a large decrease in outer medullary expression of two collecting duct water channels (aquaporin-2 and -3) and the major water channel of the thin descending limb of Henle's loop (aquaporin-1).

CONCLUSION

The concentrating defect in adriamycin-induced nephrotic syndrome in rats is a consequence of multiple defects in water and solute transporter expression, which would alter both the generation of medullary interstitial hypertonicity and osmotic equilibration in the collecting duct. Whether a similar widespread defect in transporter expression is present in idiopathic nephrotic syndrome is, at this point, untested.

LDL adsorption improves the response of focal glomerulosclerosis to corticosteroid therapy

We investigated the therapeutic effect of low density lipoprotein adsorption (LDL-A) in 14 patients who had focal glomerulosclerosis (FGS) with the nephrotic syndrome resistant to steroids. Patients received a total of 6 sessions (2 times a week for 3 weeks). The levels of total cholesterol, triglycerides and low-density lipoprotein were decreased significantly after treatment (by approximately 50%) in all patients (p<0.01). There also seemed to be a possibility that LDL-A improved the response to steroid therapy. The glomerular filtration rate (GFR) increased from 54.4 +/-27.4 ml/min to 70.0+/-30.2 ml/min (p <0.05) and daily urinary protein excretion (Up/day) decreased from 7.24+/-3.58 g/day to 2.56 + 2.00 g/day (p<0.01). Up/day was significantly higher in patients who showed more than 30% improvement of GFR (n = 6) than in patients who showed less than 30% improvement of GFR (n = 7) (9.50+/-3.41 g/day vs 4.59+/-1.17 g/day, p<0.05). The decrease of urinary protein excretion was more marked in younger patients (29.4+/-11.9 vs 49.7+/-14.8, p <0.05). Only electron microscopy was able to detect histological recovery in the patients who showed a decrease of proteinuria after LDL-A therapy and light microscopy was not able to verify or accurately identify the histological response. In conclusion, LDL-A seems to be effective for FGS associated with nephrotic syndrome resistant to steroids, especially in younger patients. Histological assessment of the effect of this treatment requires electron microscopic examination.

Intestinal absorption and biliary secretion of cholesterol in rats with nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) results in hypercholesterolemia which is attributed to increased production and decreased removal of cholesterol-rich lipoproteins. Adjustments in intestinal absorption are reportedly involved in cholesterol homeostasis. We, therefore, studied the intestinal absorption and biliary excretion of cholesterol in NS.

METHODS

We studied intestinal absorption (by in vivo perfusion and in vitro everted sac incubation techniques) and biliary secretion (by common bile duct cannulation) of cholesterol in rats with puromycin-induced NS. The results were compared with those obtained from pair-fed control (PF) animals, those given free access to food (NL) or those fed a hypercholerolemic diet (H-chol group). Micellar solutions of Krebs' phosphate buffer containing trace amounts of [14C]inulin and [3H]cholesterol, as well as different concentrations of unlabeled cholesterol, were used for absorption studies.

RESULTS

The NS and H-chol groups showed severe and comparable hypercholesterolemia. No significant difference was found in the rate of biliary cholesterol secretion among the study groups. Likewise, the rates of in vivo and in vitro cholesterol absorptions in the NS and H-chol groups were comparable with one another and similar to those found in the NL and PF groups. The rate of in vitro cholesterol absorption was directly proportional to its concentration in the incubation media at low concentrations. However, the absorption rate showed a pattern consistent with saturable transport at high cholesterol concentrations in all groups.

CONCLUSIONS

We conclude that intestinal absorption and biliary secretion of cholesterol are not appreciably influenced by either nephrotic or diet-induced hypercholesterolemia in rats. The data further suggest that cholesterol absorption may be a saturable process.

Normal growth of prepubertal nephrotic children during long-term treatment with repeated courses of prednisone

The growth of 21 prepubertal children with steroid-dependent frequently relapsing nephrotic syndrome was studied before and during treatment with repeated courses of oral prednisone for 4 y. The height and height velocity standard deviation scores (HSDS and HVSDS) of the nephrotic children were -0.11 and -0.06, respectively, at the onset of the disease and -0.12 and +0.05, +0.14 and +1.02, +0.21 and +0.78 and +0.17 and +0.66, respectively, thereafter yearly during the treatment. The mean yearly cumulative dose of prednisone was 6300, 3459, 2677 and 2081 mg/body area (m2) at the first, second, third and fourth year, respectively. The nephrotic children grew normally for their age before onset of the disease and growth remained normal despite prednisone treatment.

The nephrotic syndrome: from the simple to the complex

The nephrotic syndrome represents a series of physiological results ensuing from the occurrence of significant urinary loss of protein. Although the common initiating event of proteinuria has long been established, the list of problems that result has continued to grow as our understanding of the pathophysiology of nephrosis has increased. This article discusses this pathophysiology, emphasizing the consequences of nephrotic-range proteinuria. These consequences include not only acute and subacute manifestations of disrupted homeostasis, but also ways in which nephrosis itself may amplify mechanisms by which progressive renal nephron loss occurs. New insights into the factors that initiate and maintain glomerulosclerosis and interstitial fibrosis may offer potential approaches to preventing or ameliorating chronic renal insufficiency.