Nephrotic Syndrome

The nephrotic syndrome is a renal disease. It is defined by a triad: the presence of oedemas, a significant protéinurie (i.e. a urinary loss of Protein S higher than 3,5 grams per day) and a hypoprotidemy (drops protein concentration in the Sang with less than 60 grams per liter, the normal concentration being approximately 65 g/l). In the child, the figures selected are a protéinurie higher than 50 mg/kg/jour and a proteinemy lower than 55 g/l. The nephrotic syndrome can reveal very varied Maladie S and anatomical anomalies, and must always be explored, often by renal Biopsie.

Physiopathology

The ultrafiltration of the blood which will give the primitive Urine makes in the elementary functional unit of the Rein: the Cluster. By a physical mechanism (hydrostatic Pression, oncotic pressure) and biological (selectivity of the glomerular membrane to the blood components), the plasma is filtered through the glomerular basal Membrane and the prolongations podocytaires which paper it to form the primitive urine, which will be then successively modified by the various renal structures to give the final urine. The nephrotic syndrome is due to an anatomical or functional anomaly of the glomerular basal membrane, which is normally impermeable with proteins starting from a certain molecular weight (60000 Daltons, or 60 kDa): the loss of this selectivity involves the passage of Protéine S in the urines (which appears when the physiological capacities of tubular reabsorption of proteins are exceeded), and thus the protéinurie and the hypoprotidemy (in spite of an increased protein synthesis by the Foie). There exist schematically two large tables of anomalies:

functional anomalies, related to the loss of the negative charges of the MBG, person in charge of the nephrotic syndromes idiopathic.
the anatomical anomalies, which often testify to subjacent severe diseases.

A simple examination makes it possible to differentiate these two tables: the evaluation of the selectivity of the protéinurie. A protéinurie made up with more than 85% of Albumine (principal plasmatic protein) is known as selective, and generally raises of the functional anomalies. On the contrary, a protéinurie not functional calculus generally testifies to severe anatomical anomalies not touching only the glomerular basal membrane.

Diagnosis

The diagnosis is posed in the presence of the triad:

Protéinurie larger than 3g/24h
Hypoalbuminémie less 30g/l
Edema

Which is usually added:

Hypertriglycéridémie
Hypercholestérolémie

Consequences of the nephrotic syndrome

The hypoprotidemy is at the base of all the clinical consequences of the nephrotic syndrome:

edema S, by oncotic pressure decrease of plasma,
Infection S, when there is escape of Immunoglobuline S and complement,
increased toxicity of the Médicament S which binds to albumin, by increase in their free fraction (the fraction related to albumin is less or not active: the reduction in the albumin concentration is responsible for an increase for the free rate, and thus credit, drug.)
vascular Thrombose S, by loss of anticoagulant proteins,
Dyslipidémie S (increase in the Cholestérolémie and the triglyceridemy by stimulation of the Foie).

Assessment of first intention

This first assessment makes it possible to diagnose the most frequent causes of nephrotic syndrome and to pose the indication of a renal biopsy. It includes/understands:

a clinical examination, a interrogation, an assessment of the medicamentous catches (what makes it possible to seek a hereditary nephropathy, or a nephrotic syndrome related to a medicamentous catch)
a proportioning of the serum complement, a search for antinuclear factors (search of a Lupus or another auto-immune disease)
a proportioning of the Glycémie (detects the Diabète sweetened)
a Immunofixation of blood and urinary proteins (detects a Amylose)
a tracking HIV, Hépatite S, Syphilis, etc (post-infectious nephrotic syndrome).

At the end of this assessment, if one detected a nephrotic syndrome which had with the diabetes, with a medicamentous catch, a hereditary nephropathy, to an amylose; then the renal biopsy is not essential. In all the other cases, it will have to be realized in order to objectify the histological mechanism and anatomo-pathological of the Maladie.

Diseases responsible for nephrotic syndrome

Amylose: by abnormal starch protein deposit in the Cluster S.
nephrotic Syndrome idiopathic of the child (or of the adult): by loss of the negative charges of the membrane basal glomerular which normally push back proteins, they negatively so charged. (According to the recent epidemiological studies, there would be as many children as adults reaches of a nephrotic syndrome idiopathic)
Néphropathie diabetic: by deterioration of the capillaries related to the chronic hyperglycemia (too many Sucre in blood involves the glycation of many proteins, of which some weaken the walls of the blood capillaries, in particular of the kidneys and the Rétine).
érythémateux Lupus disseminated
Purpura rhumatoïde: the cause is still badly known, probably by deposit of complexes immunes (Immunoglobuline S.A. complexed with a Antigène) on the glomerular walls.
extra-membranous Glomerulonephritis: by deposit of immunoglobulins G and fractions of the serum complement to the external face of the glomerular basal membrane.

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