Why does blood pressure often remain near normal in patients with nephrotic syndrome?

In nephrotic syndrome, the decreased plasma oncotic pressure due to massive loss of albumin leads to fluid extravasation from the intravascular to the interstitial compartment, resulting in hypovolemia. This hypovolemia stimulates the renin-angiotensin-aldosterone system (RAAS). Angiotensin II causes vasoconstriction, sodium retention, and increased thirst, all of which tend to restore intravascular volume and thus maintain blood pressure within the normal range.

Additionally, the release of natriuretic peptides due to decreased renal perfusion and reduced glomerular filtration rate (GFR) also contributes to preserving blood pressure by inducing vasodilation and natriuresis. These compensatory mechanisms, including RAAS activation and natriuretic peptide release, often act in concert to maintain blood pressure near normal levels in patients with nephrotic syndrome.