Why Are These Gallstones Black? 

A 45-year-old female presents to the emergency department with abdominal pain and vomiting. She mentions the pain radiates to her right shoulder and has been constant for about six hours. She is febrile and the right upper quadrant of her abdomen is tender. Laboratory tests reveal leukocytosis and an abdominal ultrasound demonstrates a thickening of the gallbladder wall and the presence of gallstones. She undergoes a laparoscopic cholecystectomy and several black pigment stones are removed. When a medical student asks why these stones are black, they are told to consult the patient’s medical history and medications. Which of the following medications hints at the reasoning for the color of these stones?

A. Oral contraceptive pill
B. Pravastatin
C. Hydroxyurea
D. Metformin

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