Cardiovascularcommon
A 76-year-old woman with atrial fibrillation, whose apixaban was stopped three weeks ago after a fall, presents with four hours of severe constant central abdominal pain. She has vomited once and passed one loose bowel motion. She is distressed and asking repeatedly for stronger analgesia, yet her abdomen is soft with only mild central tenderness and no guarding. Her pulse is 110/min and irregular, blood pressure 118/76 mmHg. Blood tests show white cell count 18.5 × 10⁹/L (4.0–11.0) and lactate 3.6 mmol/L (<2.0). Which one of the following investigations is most likely to confirm the diagnosis?