Which finding is most characteristic of nephrotic syndrome?

• A. Hypertension
• B. Heavy proteinuria (>3.5 g/day)
• C. Edema
• D. Hyperlipidemia

Answer: (B)

Massive protein loss in the urine is the defining feature of nephrotic syndrome. When the glomerular filtration barrier becomes highly permeable to proteins, to the point of excreting more than about 3.5 grams per day, it signals nephrotic-range proteinuria. This substantial protein loss lowers circulating albumin, reducing plasma oncotic pressure and causing edema as fluid shifts into the interstitial space. The low albumin also stimulates the liver to make more lipoproteins, leading to hyperlipidemia. Hypertension can occur but is not as specific to nephrotic syndrome, and edema is a consequence of hypoalbuminemia rather than the defining criterion. So the most characteristic finding is heavy proteinuria (>3.5 g/day).