A 32-year-old male arrives at the trauma bay following a motor vehicle collision with severe blunt abdominal trauma. On examination, he is hypotensive (BP 85/55 mmHg), tachycardic (HR 128/min), with a distended, tender abdomen. Two large-bore IV lines are secured and fluid resuscitation initiated. Which investigation is most appropriate to confirm the diagnosis of intra-abdominal hemorrhage and guide immediate management?