[Nephrotic syndrome: pathophysiology, classification and diagnostic criteria].

The nephrotic syndrome is defined by heavy proteinuria due to abnormal increase of glomerular permeability and following hypoalbuminemia, hyperlipidemia and edema. Disorders of size selective barrier, charge selective barrier, slit diaphragm and circulating permeability factors are thought to be the causes of proteinuria. Most patients with nephrotic edema have primary salt retention. Overproduction and impaired catabolism of lipoproteins are the causes of hyperlipidemia. Abnormality of coagulation factors is also associated with nephrotic syndrome. Nephrotic syndrome may be primary or secondary to systemic disorders. Once diagnosed, the cause for the nephrotic syndrome must be examined.