Oedema
This is the usual presenting complaint of nephrotic syndrome, ranging from mild periorbital and pedal oedema to gross oedema (anasarca).
Fluid movement across capillaries is determined by the imbalance of hydrostatic and oncotic forces:
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Ph - Hydrostatic
pressure Po - Oncotic pressure At the arteriolar end of the capillary Ph > Po and at the venous end Ph < Po. Normally the net loss of fluid at the arterial end is balanced by reabsorption of fluid at the venous end of the capillary. |
The classic explanation of oedema formation in nephrotic syndrome is that the loss of albumin → a decrease in Po, favouring movement of fluid out of the capillary into the interstitium. The resultant hypovolaemia stimulates the renin-angiotensin-aldosterone system, leading to renal reabsorption of sodium and expansion of the extracellular fluid volume.
However a growing amount of evidence suggests a more important cause of oedema formation is abnormal salt and water handling by the kidneys. Click here for more information.