Ans. is 'b' i.e., USG o The prime aim of investigations in a pt. of blunt trauma abdomen is to determine whether the patient needs an exploratory laparotomy or not.o Previously DPL was the inv. of choice to determine the presence of intra-abdominal hemorrhage, but currently Ultrasound has replaced DPL,o U/S is the investigation of choice in both stable as well as unstable patients.Schwartz writes- "Blunt abdominal trauma initially is evaluated by FAST examination in most major trauma centers, and this has largely supplanted DPL. FAST is not 100% sensitive, however, so diagnostic peritoneal aspiration is still advocated in hemodynamic ally unstable patients without a defined source of blood loss to rule out abdominal hemorrhage. Patients with fluid on FAST examination, considered a 'positive FAST who do not have immediate indications for laparotomy and are hemodynamically stable undergo CT scanning to quantify their injuries. "Sabiston writes - Hemodynamically stable patients sustaining blunt trauma are adequately evaluated by abdominal ultrasound or CT unless other severe injuries take priority and the patient needs to go to the operating room before the objective abdominal evaluation. In such instances, DPL or focussed abdominal sonography for trauma (FAST) is usually performed in ike operating room to nde out intra-abdominal bleeding requiring immediate surgical exploration.Also knowo Use of U/S in trauma pts. is now k/a FAST examination (i.e. Focussed Assessment with Sonography for Trauma)In this examination the goal is not to evaluate the whole abdomen but io look for free intraperitoneal fluid at specific siteso The diagnostic approach in penetrating abdominal injuries (i.e. stab wounds & Gunshot wounds) differs from that in blunt injuries,o In Gun shot wounds (GSW)Exploratory laprotomy is mandatory, as chances of interna! injury are high (-90%) in GSWs to abdomen,o In stab wounds (SW)In contrast to GSW, SWs that penetrate the peritoneal cavity are less likely to injure intra-abdominal oigans.SWs should be explored under local anesthesia in the emergency department whether the peritoneum has been violated.Injuries that do not penetrate the peritoneal cavity do not require further evaluation.DPL can also be done to detect intraperitoneal injuries.