A child with nephrotic syndrome developed anasarca. The main cause of edema in nephrotic syndrome is:

Nephrotic syndrome: Nephrotic syndrome consists of the following: Urine protein excretion > 3 g per 24 hours Hypoalbuminemia (albumin < 3 g/dL) Peripheral edema Hyperlipidemia Oval fat bodies in the urine Peripheral edema is a hallmark of the nephrotic syndrome, occurring when the serum albumin concentration is < 3 g/dL (30 g/L). Edema is most likely due to sodium retention and, at albumin levels < 2 g/dL (20 g/L), aerial underfilling from low plasma oncotic pressure. Ref: Watnick S., Dirkx T. (2013). Chapter 22. Kidney Disease. In M.A. Papadakis, S.J. McPhee, M.W. Rabow (Eds), CURRENT Medical Diagnosis & Treatment 2013.