Treatment of nephrosis with concentrated human serum albumin. II. Effects on renal function and on excretion of water and some electrolytes

Pathophysiology, Evaluation, and Management of Edema in Childhood Nephrotic Syndrome

Generalized edema is a major presenting clinical feature of children with nephrotic syndrome (NS) exemplified by such primary conditions as minimal change disease (MCD). In these children with classical NS and marked proteinuria and hypoalbuminemia, the ensuing tendency to hypovolemia triggers compensatory physiological mechanisms, which enhance renal sodium (Na(+)) and water retention; this is known as the "underfill hypothesis." Edema can also occur in secondary forms of NS and several other glomerulonephritides, in which the degree of proteinuria and hypoalbuminemia, are variable. In contrast to MCD, in these latter conditions, the predominant mechanism of edema formation is "primary" or "pathophysiological," Na(+) and water retention; this is known as the "overfill hypothesis." A major clinical challenge in children with these disorders is to distinguish the predominant mechanism of edema formation, identify other potential contributing factors, and prevent the deleterious effects of diuretic regimens in those with unsuspected reduced effective circulatory volume (i.e., underfill). This article reviews the Starling forces that become altered in NS so as to tip the balance of fluid movement in favor of edema formation. An understanding of these pathomechanisms then serves to formulate a more rational approach to prevention, evaluation, and management of such edema.

Volumenüberladung bei Herzinsuffizienz, nephrotischem Syndrom und Leberzirrhose

Volume retention in heart failure, nephrotic syndrome, and liver cirrhosis reflects pathological changes in homeostatic mechanisms that regulate the extracellular volume (sympathetic activity, renin-angiotensin-aldosterone system [RAAS], natriuretic peptides) and plasma osmolality (antidiuretic hormone [ADH]). In heart failure and liver cirrhosis, these changes are induced by a reduction of the effective circulating volume, which is the part of the extracellular fluid that is within the arterial system and effectively perfusing the tissues. This reduction in the effective circulating volume is caused by reduced cardiac output (heart failure), or by splanchnic vasodilatation with arterial underfilling (liver cirrhosis). In both cases, baroreceptors in both the carotid sinuses and in the glomerular afferent arterioles upregulate RAAS- and sympathetic activity, resulting in systemic vasoconstriction and renal sodium (and volume) retention. More severe reductions in the effective circulating volume may additionally stimulate ADH release, thus increasing the reabsorption of free water with subsequent hyponatriemia. In nephrotic syndrome, volume retention results either directly from the primary renal disease, which induces renal sodium and volume retention ("overfilling"), or indirectly from the reduced plasma oncotic pressure due to hypoalbuminemia, which induces a fluid shift from the intravascular to the interstitial space ("underfilling") with subsequent acitivation of baroreceptors and secondary sodium and volume retention.

Postural hemodilution in nephrotic edema: a cause of spurious hemorrhage after renal biopsy

A patient with massive edema caused by nephrotic syndrome showed a nine-point decline in hematocrit after an otherwise uneventful renal biopsy. Investigation showed no evidence of hemorrhage. The decrease in hematocrit was shown to be dilutional, occurring as a result of reabsorption of edema fluid into the vascular space that occurred during the patient's prolonged recumbency after the biopsy. The phenomenon was later reproduced in this patient under study conditions. The implications of this phenomenon are discussed in light of the pathophysiology of edema formation in the nephrotic syndrome.

Extrarenal complications of the nephrotic syndrome

The systemic complications of nephrotic syndrome are responsible for much of the morbidity and mortality seen with this condition. This review discusses the causes for the hypoalbuminemia and the associated metabolic abnormalities of the nephrotic syndrome. No unifying hypothesis exists for the induction, maintenance, and resolution of nephrotic edema. In view of the wide spectrum of renal diseases leading to the nephrotic syndrome, more than a single mechanism may be responsible for the renal salt retention in these diverse conditions. Although hypoalbuminemia may be important, especially when plasma oncotic pressure is very low (serum albumin < 1.5 to 2.0 g/dL), primary impairment of salt and water excretion by the nephrotic kidney appears to be a major factor in pathogenesis of the edema. However, the decreased serum albumin and/or oncotic pressure seen with nephrotic syndrome is a major contributing factor to the development of the hyperlipidemia of nephrotic syndrome. Patients with unremitting nephrotic syndrome should be considered for combined dietary and lipid-lowering drug therapy. Urinary losses of binding proteins lead to the observed abnormalities in the endocrine system and in trace metals, and urinary losses of coagulation factors contribute to the hypercoagulable state. At present, selective renal venography is recommended when the suspicion of renal vein thrombosis is justified by clinical presentation. The impact on renal function caused by treating asymptomatic chronic renal vein thrombosis is undetermined, but anticoagulation for chronic renal vein thrombosis is associated with relatively few complications.

Edema of the nephrotic syndrome: the role of the atrial peptide system

The nephrotic syndrome is associated with an expanded interstitial volume and edema due to sodium and water retention. The mechanisms underlying these abnormalities have been only partially clarified. Renal hypoperfusion has been considered the key event that promotes avid sodium and water reabsorption by the kidney. Hypoperfusion results from hypovolemia, a consequence of urinary protein losses and decreased oncotic pressure. However, in some patients plasma volume is normal or even increased, suggesting that in such cases the cause of sodium and water retention might be independent of systemic events and possibly originates in the kidney. Experimental evidence is now available to support this, but the intrarenal mediator(s) that promote the abnormal salt retention are still not fully clear. Atrial natriuretic peptide (ANP), which increases sodium and water excretion, has been suspected to participate in fluid retention. This is consistent with experimental and human data of a markedly blunted natriuretic and diuretic response to systemic infusion of ANP in the nephrotic syndrome. Recent studies of the mechanisms of the blunted natriuretic and diuretic response to ANP documented an increased activity of renal sympathetic nerves, but the results are controversial. The altered response to ANP also may be related to a defect in the number and affinity of receptor-binding sites for the peptide. Evidence also is available of a possible defect at the level of intracellular cyclic guanosine monophosphate, the second messenger of ANP. The gene encoding for a cyclophilin-like protein, which is increased in sodium-retaining conditions, is upregulated in the kidneys of nephrotic rats, and the infusion of ANP further increases cyclophilin-like protein mRNA. Thus, multiple factors probably act in concert to induce edema formation in the nephrotic syndrome. In this review we specifically address the tubular insensitivity to the natriuretic and diuretic action of ANP, which could be an important initiating event and could possibly contribute to sustaining the edema.

When is serum albumin worth measuring?

This paper critically examines the usefulness of serum albumin measurement in the light of current laboratory practice and knowledge of the pathophysiology of albumin metabolism. The main conclusions and recommendations are as follows: (i) Albumin measurement forms a limited, but useful part of the investigation of liver disease; a normal serum albumin concentration makes the diagnosis of cirrhosis unlikely, while a low level in viral hepatitis suggests either severe hepatocellular damage or other complications. (ii) Albumin measurement is essential in selecting patients for, and in determining the amount and frequency of, albumin replacement. (iii) Serum albumin concentration provides a useful indication of prognosis in myeloma. (iv) In the long-term management of patients undergoing enteral or parenteral nutrition, serum albumin concentration is one of several parameters which, together, are useful in predicting the outcome of treatment. (v) The serum albumin concentration may provide a clue to the aetiology of unexplained oedema. (vi) Serum albumin measurement is useful in indicating the level of ionised calcium and of unbound unconjugated bilirubin.

Evidence that some mechanism other than the renin system causes sodium retention in nephrotic syndrome

8 of 16 patients with nephrotic syndrome had normal or low plasma renin activity while spontaneously retaining sodium. The other 8 patients had a high plasma renin activity which may have caused the sodium retention. Oral captopril and albumin infusion given separately both suppressed the renin system in these patients. Despite this, urinary sodium excretion remained less than sodium intake and patients continued to retain sodium and gain weight. These results suggest that, even in patients with nephrotic syndrome who do have stimulation of the renin angiotensin system, some other overriding mechanism is responsible for sodium retention. Therefore it seems unlikely that angiotensin-converting enzyme inhibitors will be useful in the treatment of sodium retention in nephrotic syndrome.

Nephrotic syndrome

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Effects of infusion of hyperoncotic dextran in children with the nephrotic syndrome

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