Question

Why would a patient with nephrotic symptoms have systemic edema?

Answer 1

Yes, nephrotic symptoms include excess fluids in the body, and systemic edema is a abnormal accumulation of fluids in the skin :D

Answer 2

Proteinuria - Lot of albumin is lost in urine in Nephrotic Syndrome.
Albumin is an important component of blood which maintains capillary hydrostatic-osmotic pressure balance. This is disrupted in Nephrotic Syndrome as lot of protein is lost in urine. This causes water to move into tissues and produce edema.
Along with that Oliguria- IE:decreased excretion of water causes water retention and add to the effect.