A 54-year-old patient complains of weakness, jaundice, itching skin. Disease onset was 1.5 months ago: fever up to 39°C appeared at first, with progressive jaundice developed 2 weeks later. On hospitalization jaundice was severely progressed. Liver cannot be palpated. Gallbladder is enlarged and painless. Blood bilirubin is 190 mcmol/L (accounting mainly for direct bilirubin). Stool is acholic. What is the most likely reason for jaundice in this patient?