How does refeeding syndrome cause pitting edema?

Question

In the answer to "How do you feed a starving person in a way that won't kill them?", it is mentioned that refeeding syndrome can cause peripheral edema. How does this occur?

Answer 1

During refeeding syndrome (RFS), intake of carbohydrates causes a massive surge in insulin levels, leading to electrolyte abnormalities. Increased insulin also caused sodium and water retention independent to changes of renal GFR and RPF [1]. Water retention increases capillary hydrostatic pressure, leading to peripheral edema.

Another possible contributor to peripheral edema during RFS is hypoalbuminemia, which decreases capillary oncotic pressure [2].

Sources:

1. "The Effect of Insulin on Renal Sodium Metabolism". R.A. DeFronzo
2. "Refeeding syndrome". J. Fuentebella, J.A. Kerner