A 45-year-old male with a 1-year history of cirrhosis presents with abdominal distension for 1 month. Examination reveals ascites, non-palpable liver, and spleen 2 cm below the costal margin. One day before admission, he developed sudden severe abdominal pain followed by fever, hematochezia, shock, rapid increase in ascites, and splenomegaly. The most likely complication is: