A 65-year-old man with a history of alcohol abuse has had hematemesis for the past day. Physical examination reveals mild jaundice, spider angiomas, and gynecomastia. He has mild pedal edema, normal jugular venous pulsation (JVP), and a massively distended abdomen. Paracentesis is performed and the fluid obtained shows accumulation of protein-poor fluid that is free of inflammatory cells. Which of the following factors is most likely to be responsible for the collection of abdominal fluid in this man?