Question category: Gastroenterology
A 68 year old male presents with severe colicky abdominal pain. Surprisingly there is only minimal generalised tenderness and no evidence of guarding. He gives a history of weight loss and pain after eating for the last 6 months. He has previously had a myocardial infarction. His bloods reveal raised inflammatory markers and a metabolic acidosis. What investigation would be most useful for the definitive diagnosis?