Gastroparesis

A 28-year-old woman comes to the emergency department with nausea and vomiting. Over the past few months, the patient has experienced episodes of nausea that occur primarily after eating meals and gradually resolve after a few hours. Tonight, 20 minutes after dinner, the patient experienced a sudden onset of abdominal pain with nausea and regurgitated the majority of her meal; the nausea has persisted. The patient has not had a bowel movement in 3 days. She has a history of type 1 diabetes which was diagnosed at age 12; it has been well managed with a strict insulin regimen delivered by an insulin pump. The patient also takes a multivitamin each evening. The patient’s temperature is 37.0°C (98.6°F), pulse is 80/min, respirations are 16/min, and blood pressure is 115/75 mmHg. Physical examination reveals the patient to be thin and uncomfortable, with a tender epigastrium and mild abdominal distention. Laboratory studies show a normal complete blood count, normal comprehensive metabolic profile, and negative urine β-hCG (human chorionic gonadotropin). Which of the following is the most likely underlying cause of this patient’s symptoms?