Peritonitis

A 56-year-old woman is diagnosed with stage IV cholangiocarcinoma, for which she is receiving chemotherapy. Periodically, the patient develops ascites, for which abdominal paracentesis is performed. However, the patient was lost to follow-up. The patient is brought to the emergency department by her daughter with diffuse abdominal pain, nausea, vomiting, and altered mental status. On admission, temperature is 38.6°C (101.5°F), pulse is 100/min, respirations are 22/min, and blood pressure is 120/66 mm Hg. On physical examination, the abdomen is distended and shifting dullness and a fluid wave are present. There is diffuse guarding with abdominal palpation. Which of the following is the most likely cause of this patient’s symptoms?