A 5-year-old boy presents with progressive periorbital swelling for 4 days followed by pedal edema and abdominal distension. Blood pressure is normal. Urinalysis shows 4+ protein with no RBCs. Serum albumin is 1.6 g/dL and cholesterol is elevated. Which mechanism best explains the edema in this child?
A
Reduced plasma oncotic pressure leading to fluid shift into interstitial space
B
Increased capillary hydrostatic pressure due to hypertension
C
Primary renal sodium loss
D
Excess erythropoietin production