Surgery and Perioperative Caremiddle twist
A 22-year-old woman presents to the emergency department with 24 hours of lower abdominal pain that began around the umbilicus and is now most marked on the right side, associated with nausea and loss of appetite. Her menstrual cycles are regular and her last period was two weeks ago. On examination her temperature is 37.8°C and pulse 92/min, with tenderness and guarding in the right iliac fossa. Urine β-hCG is negative and urinalysis shows a trace of leucocytes only. Which one of the following is the most appropriate initial investigation?