Quelling the Swelling

A 66 year old male with a history of compensated alcohol-related cirrhosis presents with abdominal swelling and a ten pound weight gain but denies any other symptoms. His exam is notable for normal vital signs and abdominal distension, and labs show an increase in his MELD-Na from 11 to 17, primarily due to an increased bilirubin and INR. AST and ALT are 17 and 13, respectively. What is the most likely cause of his acute decompensation?