What is mechanism of fluid accumulation causing pulmonary edema?

Depends on balance of hydrostatic and oncotic pressures of pulmonary capillaries and surrounding tissues. Hydrostatic favors fluid to move from capillaries to interstitium, oncotic (protein concentration) favors moving to vessels. Cirrhosis, nephrotic syndrome cause low plasma proteins, causing hydrostatic fluid to go out, in addition, disruption of endothelia will allow proteins to go out of capillaries into tissue causing pulmonary edema (hydrostatic alone isn't enough for edema)