This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Trauma, Subject name: Surgery
Investigation of choice to exclude intra-abdominal bleeding in hemodynamically unstable patient is - 
Select and explain. 
A. Diagnostic peritoneal lavage, B. FAST, C. CT Scan, D. X Ray
B: FAST
Answer: B: FAST 
Explanation: Ans. is 'b' i.e., FAST Investigations to rule out abdominal injury in trauma patient* Investigations are driven by the cardiovascular status of the patient.* Blood loss into the abdomen can be subtle and there may be no clinical signs (blood is not an irritant and may not initially cause any abdominal pain). If stable, the best and most sensitive modality is a CT scan with intravenous contrast; however, in the unstable patient, this is generally not possible.A) Hemodynamically stable patient - CT with contrastB) Hemodynamically unstable -# Provision for FAST available and reliable operator - FAST# Provision for FAST unavailable and/ or unreliable operator - Diagnostic peritoneal lavage