Nephrotic syndrome
| Nephrotic syndrome | |
|---|---|
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| Histopathological image of diabetic glomerulosclerosis the main cause of nephrotic syndrome in adults. H&E stain. | |
| Classification and external resources | |
| Specialty | Nephrology |
| ICD-10 | N04 |
| ICD-9-CM | 581 |
| DiseasesDB | 8905 |
| MedlinePlus | 000490 |
| eMedicine | med/1612 ped/1564 |
| MeSH | D009404 |
Nephrotic syndrome is a syndrome comprising signs of nephrosis, chiefly proteinuria, hypoalbuminemia, and edema. It is a component of glomerulonephrosis, in which different degrees of proteinuria occur. Essentially, loss of protein through the kidneys (proteinuria) leads to low protein levels in the blood (hypoproteinemia including hypoalbuminemia), which causes water to be drawn into soft tissues (edema). Severe hypoalbuminemia can also cause a variety of secondary problems, such as water in the abdominal cavity (ascites), around the heart or lung (pericardial effusion, pleural effusion), high cholesterol (hence hyperlipidemia), loss of molecules regulating coagulation (hence increased risk of thrombosis).
Large proteinuria is due to an increase in permeability of the filtering membrane of the kidney which normally separates the blood from the urinary space in Bowman's capsule. This is composed of the capillary walls of the glomerulus which are wrapped by highly specialized cells called podocytes. Alterations in their capacity to filter the substances transported in the blood mean that proteins but not cells pass into the urine (hence no haematuria). By contrast, in nephritic syndrome red blood cells pass through the pores, causing haematuria.
Nephrotic syndrome is characterized by large proteinuria (>3.5 g per 1.73 m2 body surface area per day, or > 40 mg per square meter body surface area per hour in children), hypoalbuminemia (< 2,5 g/dl), hyperlipidaemia, and edema (which is generalized and also known as anasarca or dropsy) that begins in the face. Lipiduria (lipids in urine) can also occur, but is not essential for the diagnosis of nephrotic syndrome. Hyponatremia also occurs with a low fractional sodium excretion.
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