A 45-year-old woman comes to the emergency department due to sudden-onset abdominal pain. The patient had just finished dinner when she started to experience severe pain in the upper right side of her abdomen associated with nausea and vomiting. The pain radiates to her right shoulder. The patient recently had 2 similar episodes with less intense pain that resolved spontaneously within several hours. She has a history of hyperlipidemia and type 2 diabetes mellitus. The patient lost 15 kg (33.1 lb) after undergoing a laparoscopic Roux-en-Y gastric bypass surgery 5 months ago. She does not use tobacco, alcohol, or recreational drugs. Temperature is 37.8 C (100 F), blood pressure is 140/92 mm Hg, pulse is 112/min, and respirations are 18/min. Heart sounds are normal without murmurs, and the lungs are clear to auscultation. Abdominal examination shows multiple small, well-healed surgical scars. Right upper quadrant tenderness is present. Bowel sounds are active. Stool is guaiac negative.