Sequential nephron blockade breaks resistance to diuretics in edematous states

Diuretic therapy in edematous diseases often yields an inadequate natriuretic response ("diuretic resistance"). To study the functional changes in patients with congestive heart failure, liver cirrhosis with ascites, and nephrotic syndrome, characterized by a reduced effective arterial blood volume (EABV), different diuretic strategies were studied. It was shown that monotherapy with hydrochlorothiazide or furosemide was followed by an inadequate natriuretic response. Correlation of diuretic response with pretreatment fractional sodium excretion of the patient revealed a clear-cut interdependency: Those patients were resistant whose FENa+ was greatly below normal (<0.2%). In addition, it was found that the coadministration of the carboanhydrase inhibitor acetazolamide to diuretic therapy was very effective. We therefore conclude that an increase in proximal-tubular Na+ reabsorption is the major ("pharmacodynamic") determinant for diuretic resistance in edematous diseases with functional "underfilling" of the vascular tree. This alteration of the kidney can easily be overcome by coadministration of a carboanhydrase inhibitor (e.g., acetazolamide).

Increased renal excretion of endothelin-1 in nephrotic patients

BACKGROUND

Renal function is influenced by direct and indirect action of endothelins. They reduce renal blood flow and glomerular filtration. The aim of the present study was to determine plasma and urinary endothelin-1 (ET-1) in two major categories of renal patients and to compare them with normal subjects.

METHODS

Endothelin-1 was measured in the plasma and urine of patients with chronic renal disease and reduced glomerular filtration rate (GFR), and in patients with proteinuria due to glomerular dysfunction with unaffected GFR. A group of healthy subjects was used as a reference.

RESULTS

Plasma endothelin-1 was increased in all patients to 60 +/- 13 pg/ml independent of GFR compared to 29 +/- 5 pg/ml in normal subjects (P < 0.001). The endothelin-1 load was decreased to 1190 +/- 450 pg/ml/1.73 m2 in patients with reduced GFR, compared to 2780 +/- 690 pg/ml/1.73 m2 of normal subjects, whereas in patients with glomerular damage and normal GFR, it was increased to 5480 +/- 1910 pg/ml/1.73 m2 (P < 0.01). ET-1 was found to be excreted and reabsorbed by the renal tubules by the same mechanisms as sodium and potassium, because its secretion fraction changes in parallel to those of the above ions. The excreted endothelin increased to 730 +/- 420 and 710 +/- 250 pg/ml/1.73 m2 (P < 0.01) in the two categories of patients respectively, compared to 290 +/- 100 pg/ml/1.73 m2 in the normal group. The excretion fraction of patients with normal GFR was similar to normal subjects, while it appeared to increase in patients with reduced GFR (P < 0.01).

CONCLUSIONS

In the development of renal disease the plasma endothelin concentration is independent of the renal filtration capability and endothelin may be involved in functional and anatomical changes of the kidney as a causal factor or resulting from the renal disease.

Over 11 years of stable renal function after remission of nephrotic-range proteinuria in type I diabetics treated with an ACE inhibitor

It has previously been considered inevitable that a progressive deterioration in renal function would occur in type I diabetics who have proteinuria in the nephrotic range. We have reviewed all type I diabetic patients presenting with nephrotic-range albuminuria to this department over a 13-year period. Of 16 patients identified, 4 have demonstrated a prolonged stability of renal function, with 2 losing their albuminuria. The latter 2 patients, who have been treated with an angiotensin-converting enzyme inhibitor for over 11 years, are presented in detail. The possible factors contributing to progression and the role of angiotensin-converting enzyme inhibitors in the treatment of advanced diabetic nephropathy are discussed.

Steroid-resistant nephrotic focal segmental glomerulosclerosis: a treatable disease

If not aggressively treated, oral steroid-resistant (SRst) nephrotic focal segmental glomerulosclerosis (FSGS) is likely to progress to end-stage renal failure. Three observations challenge the conclusion of the International Study of Kidney Diseases in Children (ISKDC) that SRst FSGS is unresponsive to further immunosuppression: (1) The ISKDC definitions of response and relapse, which fit the patterns in minimal change disease, precluded appropriate recognition of partial or gradual responses. (2) In two ISKDC studies, a small number of children with FSGS in one case, and the use of a year of alternate-day prednisone as a control in the other, may have obscured the effects of cyclophosphamide. (3) Recent studies of more aggressive therapies have provided strong evidence of benefit. High-dose methylprednisolone infusion therapy, with alternate-day prednisone alone or with alternate-day prednisone plus an alkylating agent (the M-P/ triple therapy protocol) has achieved sustained, complete remissions with stable renal function in 66% of children with SRst FSGS, and near-complete resolution of proteinuria in another 9%. Cyclosporine (CsA) plus alternate-day prednisone has produced complete or near-complete remissions in 35% of similar cases. Whether or not controlled studies will confirm the apparently greater efficacy of the M-P/triple therapy protocol, the favorable outcomes with both the M-P and the CsA regimens support the conclusion that a conservative approach to SRst FSGS is no longer appropriate.

Hemostatic profile in nephrotic syndrome

OBJECTIVE

To evaluate the coagulation profile and its relation to steroid therapy, and the frequency of thromboembolic complications and its correlation with coagulation parameters in nephrotic syndrome (NS).

SETTING

Hospital based.

SUBJECTS AND METHODS

Forty children with NS were subdivided into four groups, namely, fresh cases, steroid dependent, remission after therapy and steroid resistant. An equal number of age and sex matched children served as controls. In all the study and control subjects, detailed clinical examination, liver function tests, renal function tests and detailed coagulation profile were done. Evaluation of renal veins and inferior vena cava for the presence of thrombosis was also done by abdominal ultrasonography.

RESULTS

Thrombocytosis was detected in 57.5% and the degree of thrombocytosis was directly related to the amount of proteinuria. The mean prothrombin and thrombin times were within normal range in the study children. The activated partial thromboplastine time (APTT) was prolonged in six cases (15%) and three out of these six children had thromboembolic complications. Antithrombin-III level was significantly lower (p < 0.001) whereas protein C and S were significantly elevated (p < 0.001) as compared to controls. The levels became normal with remission of the disease. Steroid therapy significantly increased the levels of proteins C, protein S. AT-III and fibrinogen as compared to controls. Thromboembolic complications were seen in 3 cases (7.6%) and were associated with very low levels of AT-III and protein C and all three had serum albumin below 2 g/dl.

CONCLUSIONS

The importance of coagulation profile in nephrotic syndrome is highlighted and a high index of suspicion for thromboembolic complications is warranted in patients with thrombocytosis, hyper fibrinogenemia, prolonged APTT and in children with low levels of AT-III, protein C and protein S.

Changes in serum lipoprotein(a) levels in children with corticosensitive nephrotic syndrome

Variations in lipoprotein(a) [Lp(a)] levels were evaluated during the course of the nephrotic syndrome in 20 children (17 males, 3 females, aged 2-16 years), to evaluate the use of this parameter in the prognosis and monitoring of the disease. One patient was in relapse, 12 in remission, and 7 alternated between remission and relapse. Results were compared with those obtained in a control population of 100 age-matched children. Lp(a) was measured by a previously described immunonephelometric technique. Serum Lp(a) levels were increased in children with relapsing nephrotic syndrome compared with controls (median value of 419 mg/l vs. 86 mg/l). The median Lp(a) level in patients with nephrotic syndrome in remission was different from controls (270 mg/l under steroid therapy and 163 mg/l without steroid therapy), but remained within the reference range. Of the patients in relapse, 66% had Lp(a) levels above the generally accepted limit for cardiovascular risk of 300 mg/l, compared with 16% of controls, 44% of patients with nephrotic syndrome in remission under steroid therapy, and 18% of patients with nephrotic syndrome in remission without steroid therapy. In 2 patients, Lp(a) was measured repeatedly and was significantly higher during the acute phase of the disease (up to sixfold basal level). Changes in Lp(a) levels correlated with cholesterol levels, but the kinetics and the extent of variations were different. These data suggest that measurement of Lp(a) is useful for monitoring the nephrotic syndrome in children, particularly for detecting complications.

Proteinuria and albumin homeostasis in the nephrotic syndrome: effect of dietary protein intake

Nephrotic syndrome is analyzed in the light of interventions designed to decrease proteinuria and renal injury. The effect of dietary protein intake on urinary protein losses and albumin homeostasis are discussed on the basis of the pathophysiologic mechanisms known to account for changes in renal function of nephrotic patients. In addition, the effect of angiotensin-converting enzyme inhibitors for reduction of proteinuria is discussed in terms of the modulation of glomerular permselectivity and hemodynamics.

Coagulopathy of childhood nephrotic syndrome--a reappraisal of the role of natural anticoagulants and fibrinolysis

In an attempt to characterise further the coagulopathy of childhood nephrotic syndrome, this study concentrates on simultaneous measurements of the natural anticoagulants [antithrombin III (ATIII), proteins C and S] and the fibrinolytic factors, tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI). The study groups consisted of 41 children (ages ranging from 2 to 14 years; median 7.1) in the relapse of nephrosis and 48 children (ages ranging from 3 to 14 years; median 7.6) in remission. The results obtained were compared with normal values obtained in healthy age- and sex-matched controls (n = 103). During relapse, there was a marked increase in the plasma level of fibrinogen, protein C, and protein S and reduced plasma ATIII level; tPA level was similar to control but PAI level exhibited a significant reduction. During remission, the protein C level either remained elevated or increased further, but some decreased. Protein S and plasma ATIII level normalised. The fibrinolytic activator tPA dropped slightly but the PAI level remained significantly below control levels. We conclude that in the relapse of childhood nephrosis, despite the existence of a significant prothrombotic tendency as featured by hyperfibrinogenaemia and markedly reduced ATIII level, the simultaneous elevation of the natural anticoagulant, protein C level and enhanced fibrinolysis that persist until the remission phase, seem to be major preventive mechanisms guarding nephrotic children against thromboembolic phenomena.

Growth hormone, the insulin-like growth factor system, and the kidney

GH receptors, IGFs, and IGF-receptors are expressed in the kidney. Their location in the different parts of the nephron suggests autocrine or paracrine as well as endocrine modes of action. A lack of GH receptors and probably of IGF-I synthesis in glomeruli in vivo suggest that all glomerular GH and IGF-I effects are mediated by circulating IGF-I through endocrine modes. GH and IGF-I increase GFR in normal rats and humans, and increase phosphate and possibly sodium reabsorption in normal and diabetic subjects. During normal renal development GH, IGF-I, and IGF-II appear to play a role. GH and IGF-I cause kidney growth, and circulating and/or renal IGF-I appear to contribute to renal hypertrophy and compensatory renal growth in experimental animal models. GH may contribute also to glomerular sclerosis and progression of renal failure in experimental models. In patients with chronic renal failure such a role of endogenous or exogenous GH has not yet been convincingly proven. In chronic or acute renal failure and in the nephrotic syndrome there are complex abnormalities in the systemic and renal IGF/IGFBP-system. In chronic renal failure there is resistance to GH and IGF-I that can be overridden by pharmacological administration of each of the peptides. GH is used therapeutically in children with chronic renal failure to accelerate growth. GH and IGF-I may be useful agents to improve nitrogen balance and nutritional status in patients with chronic renal failure. In rats with ARF, administration of IGF-I accelerates the recovery of renal function. Whether this treatment is also successful in patients with ARF remains to be demonstrated by ongoing clinical trials.

Treatment of nephrotic adults with a supplemented, very low-protein diet

Optimal dietary protein intake for adults with the nephrotic syndrome has not been established; very low-protein diets are believed to be contraindicated. Sixteen patients with the nephrotic syndrome were nevertheless prescribed a very low protein diet (0.3 g/kg) supplemented by 10 to 20 g/d essential amino acids (or, in a few cases, ketoacids) for an average of 10 months (range, 1 to 36 months). In 11 patients with initial glomerular filtration rates (GFRs) < or = 30 mL/min/3 m2 of height (ht)2, significant but modest improvement was seen (on the average) in proteinuria, serum albumin, and serum cholesterol; all 11 eventually went on to dialysis. The other five patients, with initial GFRs of 32 to 69 ml/min/3 m2 of ht2, had either focal segmental glomerulosclerosis, diabetic nephropathy, or, in one patient, both. The nephrotic syndrome associated with these disorders rarely remits spontaneously. However, during the following 3 to 15 months mean proteinuria decreased from 9.3 to 1.9 g/d, mean serum albumin increased from 2.5 g/dL to 3.8 g/dL, and mean serum cholesterol decreased from 415 mg/dL to 255 mg/dL (all P < 0.001). The GFR either remained constant or increased. Four of these five patients have resumed normal or nearly normal diets and remain in remission or near-remission for 6 to 24 months. We conclude that severe protein restriction plus an essential amino acid supplement may induce prolonged remission in adults with the nephrotic syndrome provided that GFR is not severely reduced. The mechanism of this paradoxical response to protein restriction remains to be determined.

[Verification of indications for kidney biopsy in children with steroid-dependent nephrotic syndrome]

The aim of this study was to assess if cytostatic treatment of steroidodependent nephrotic syndrome in children should be preceded by renal biopsy. The result of treatment of 75 children with steroidodependent nephrotic syndrome were analysed. They were randomized for treatment with chlorambucil and cyclophosphamide and divided into two groups. Group I includes 32 children without preceding biopsy, group II, 43 children with established histopatologic diagnosis. Remission was achieved by 25 (78%) children in group I (15 (79%) of 19 treated with chlorambucil and 10(77%) of 13 treated with cyclophosphamide) and 38 (88.4%) in group II (25 (96%) of 26 treated with chlorambucil and 13 (76%) of 17 treated with cyclophosphamide). The results of therapy in children of two groups are comparable. This would indicate that a trial of cytostatic treatment can be started without previous renal biopsy.

Phosphodiesterase activity as a mediator of renal resistance to ANP in pathological salt retention

Resistance to the natriuretic action of atrial natriuretic peptide (ANP) is a hallmark of states of pathological sodium retention including congestive heart failure, cirrhosis of the liver, and nephrotic syndrome. A variety of mechanisms including reduced delivery of filtrate to ANP-sensitive sites in the inner medullary collecting duct and diminished receptor density in this tubular segment have been offered to account for this resistance. Recent studies in experimental nephrotic syndrome and in liver disease produced by ligation of the common bile duct in rats suggest that increased activity of cyclic guanosine 3',5'-monophosphate (cGMP) phosphodiesterase may be an important mediator of renal resistance to ANP. Such increased enzyme activity rapidly catabolizes the second messenger cGMP, normally formed when ANP interacts with its biologically active natriuretic peptide A receptors, thereby leading to blunted ANP responsiveness. This increased phosphodiesterase activity offers a novel approach to the management of clinical conditions associated with sodium retention and edema formation.

Characteristics of renal sympathetic nerve activity in sodium-retaining disorders

Characteristics of renal sympathetic nerve activity in conscious rats with established congestive heart failure, cirrhosis, or nephrotic syndrome were analyzed using three methods: mean integrated voltage over time, power spectrum analysis, and sympathetic peak detection analysis. Compared with control rats, all three disease models had increased mean integrated voltage. On power spectrum analysis, all three disease models had increased relative power at the heart rate frequency, indicating that it was related to renal sympathetic nerve discharge coupled to the cardiac cycle. Congestive heart failure and nephrotic syndrome rats showed increased relative power in the low-frequency range, whereas cirrhotic and nephrotic syndrome rats showed decreased relative power in the high-frequency range. On sympathetic peak detection analysis, the frequency of sympathetic peaks was greater in the three disease models compared with the control rats. In cirrhotic rats, the distribution of sympathetic peak heights was shifted toward an increased number of peaks of lesser height. It is concluded that basal renal sympathetic nerve activity is chronically increased in these disease models. This is manifest as increased power coupled to the cardiac cycle, which may reflect the disease-specific defects in arterial and cardiac baroreflex control. In cirrhosis, there is possible selective activation of a subgroup of renal sympathetic nerve fibers.

Renal amyloidosis--a clinicopathologic study

A total of 19,075 necropsies and 1169 renal biopsies were scrutinised over a period of 20 years (1973-1992) retrospectively with an aim to study the incidence and pattern of renal amyloidosis in Nair Hospital. A total of 75 cases with amyloidosis were detected, 33 from the necropsy series (0.162%) and 42 from biopsies (3.59%). Secondary amyloidosis was seen in 82.66% and primary amyloidosis in 10.66%. Tuberculosis of various organs was the main cause of secondary amyloidosis (79.03%). Nephrotic syndrome was the common mode of presentation (52%). Besides kidney, which were involved in all cases, the liver, spleen and adrenals were other commonly involved organs at necropsy. Renal failure was the leading cause of death (51.51%). Thioflavine-T proved to be more sensitive technique than other conventional staining methods. The potassium permanganate test is a useful test to distinguish secondary amyloid fibrils from other amyloid fibrils. Abdominal fat aspiration may prove to be specific, sensitive and a routine procedure enabling the early diagnosis of amyloidosis leading to increased incidence of amyloidosis during life than at necropsy.

The primary glomerulopathies

Disorders of glomerular structure and function are encountered frequently in clinical medicine. Many arise as part of a well-defined multisystem or multi-organ disease process, while in others the clinical and laboratory manifestations are consequent to the sole or predominant involvement of glomeruli. The latter are known as the primary glomerulopathies. These disorders can evoke a variety of clinical syndromes, including acute glomerulonephritis, rapidly progressive glomerulo-nephritis, nephrotic syndrome, "symptomless" hematuria and/or proteinuria, and chronic glomerulonephritis. The identification of underlying morphology, through the application of renal biopsy techniques, can provide useful information for both prognosis and treatment. Pathogenic mechanisms involved in the primary glomerulopathies are varied, but immunologic perturbations underlie many disease entities. This article describes the clinical features, pathology, natural history, and treatment of the main categories of primary glomerulonephritis, with emphasis on recent developments and practical aspects of diagnosis and management.

Atrial natriuretic peptide, sodium retention, and proteinuria in nephrotic syndrome

BACKGROUND

Oedema formation in the nephrotic syndrome is primarily due to tubular sodium retention. The pathogenetic role of alpha atrial natriuretic peptide (ANP), a hormonal promoter of natriuresis is unknown.

METHODS

In 31 patients (aged 35+/-11 years) with nephrotic syndrome and histopathological evidence of primary glomerulonephritis, we investigated plasma ANP concentration and its influence on renal haemodynamics, natriuresis, and proteinuria (total protein, albumin, IgG excretion). Patients with a compensated treated form of nephrotic syndrome due to primary glomerulonephritis were included in the study. Serum creatinine levels were <=1.4 mg/dl. Diuretic medication was discontinued at least 24 h before the investigation was started. Patients were randomly assigned to ANP infusion (0.005 microg/kg*min; group II, n=15) or received placebo (group III, n=16). Ten healthy subjects (group I) served as normal controls.

RESULTS

In normal subjects (group I), ANP caused an increase in natriuresis from 14.5+/-4.2 mmol/h to 26.4+/-11.1 mmol/h (P<0.01). In patients with nephrotic syndrome (group II), baseline sodium excretion of 10.5+/-6.0 mmol/h was increased to 19.6+/-14.8 mmol/h with ANP infusion (P<0.01). No changes were seen in the placebo group III. The absolute increase in ANP induced natriuresis was not significantly different between group I and II. However, plasma ANP levels were significantly higher in patients with nephrotic syndrome (166+/-87 pg/ml vs. 74+/-21 pg/ml, P<0.05) and also reached higher levels after ANP infusion (P<0.01). Therefore, natriuresis was significantly reduced when circulating ANP levels were taken into account (P<0.05). ANP administration resulted in an increase of total protein excretion in patients with the nephrotic syndrome (group II, from 219+/-277 mg/h to 264+/-268 mg/h). Albumin elimination rose from 128+/-151 mg/h to 167+/-170 mg/h (P<0.05) and IgG excretion from 4.91+/-6.67 mg/h to 9.27+/-10.78 mg/h (P<0.05). Healthy subjects also showed a small but significant increase in albuminuria (48+/-38%, P<0.05). Low-dose ANP infusion did not, however, induce any significant alteration in GFR, ERPF and blood pressure.

CONCLUSION

ANP plasma concentrations in the steady state are elevated in patients with the nephrotic syndrome. The natriuretic effect of ANP is reduced when referring to circulating ANP plasma levels. Elevated ANP levels enhance urinary protein excretion in the nephrotic syndrome. This is not due to modulation of GFR or FF, but is most probably attributable to increased glomerular permeability.