A 32 year old woman undergoes a gastric bypass operation for morbid obesity. The surgery goeswell and she loses 70 kg in two months. She has two children; the youngest was delivered by
caesarean section 2 years ago. She comes into the emergency room complaining of intermittent
episodes of right upper quadrant abdominal pain. The physical exam is remarkable for right upper
quadrant tenderness. Liver function studies are normal. A right upper quadrant ultrasound shows
numerous mobile structures with acoustic shadowing in the gallbladder. The bile duct is not
dilated.
The most likely risk factor for this patient’s condition is which of the following?
