A 58-year-old woman from Bangalore with a 20-year history of gallstones presents with postprandial right upper quadrant pain and steatorrhea (fatty stools). Abdominal imaging confirms a large gallstone impacted in the common bile duct. Laboratory findings show: total bilirubin 3.2 mg/dL, direct bilirubin 2.8 mg/dL, ALP 320 U/L, and 72-hour fecal fat 18 g (normal <7 g). Which of the following best explains the mechanism of steatorrhea in this patient?