The decision to obtain a CT depends on the mechanism of injury, the response to initial fluid resuscitation, and the surgeon’s judgment of whether or not information gained from CT would be useful or would alter the management plan.

In the hemodynamically normal patient with a gunshot wound on physical examination, if estimation of trajectory on biplanar plain radiographs suggest peritoneal traverse and there is no evidence of intrathoracic or spinal injury, a preoperative CT is usually not required or helpful. As mentioned before, a negative FAST does not rule out active hemorrhage. In the hemodynamically normal patient with a suspected tangential trajectory, CT may give enough information to the surgeon to avoid laparotomy. In the hemodynamically normal patient with a transmediastinal trajectory or a suspected thoracic vascular injury, CT scanning may also be helpful.

In the blunt trauma patient with a positive FAST, the decision to obtain a CT scan is based on the response to initial fluid resuscitation. Although the imaging time has been reduced with the new generation of multi-detector spiral CT scans to the point of being insignificant, the time and effort required to transport and position the patient remains unchanged and is long enough that the patient may deteriorate with resulting increased morbidity and mortality (Fig. 4.2). If there is suspicion of ongoing bleeding based on information gathered in the trauma room, it is important that a trauma team member continues to direct the resuscitation process in CT. While not a widespread practice, quick bedside estimation of the degree of hemoperitoneum on FAST can be a useful adjunct for the surgeon to decide if there is a need to rapidly transport a patient to the operating room without CT (Table 4.1) [6, 7].