At this juncture, only CT scanning can make the diagnosis of organ-specific injury in the abdomen. CT scanning images both the intraabdominal content and the retroperitoneum. Thus it is the diagnostic test of choice to investigate the duodenum and pancreas. In addition, it has almost completely supplanted use of the intravenous pyelogram (IVP) in the evaluation of urologic injuries. It is a more complete examination than IVP and assesses the status of the renal vasculature. It can diagnose urinary extravasation and images the ureters most of the time. It can quantitate the amount of blood in the abdomen and can image the individual organs with precision.
The disadvantages of CT are the expense and time required to perform the examination. In many centers, the CT scanner may be located some distance away from the emergency department, mandating transport of patients out of a monitored setting. This may limit the utility, particularly in critically ill patients. An additional disadvantage is the oral contrast material, which often produces nausea and vomiting or must be administered while the spine remains immobilized, and the intravenous contrast material, which has a small incidence of allergic reactions. Some have advocated that oral contrast is unnecessary for abdominal CT during the initial assessment.11 While some institutions have adopted this practice or apply it only to selective patients, omission of oral contrast in the CT evaluation of blunt abdominal trauma requires further study before it is likely to gain widespread acceptance.
There are some patients who require CT scanning despite a normal ultrasound exam. Chiu and colleagues have demonstrated that up to 28 percent of all patients with specific physical findings or injury complexes may have intraabdominal solid visceral injury without hemoperitoneum. 12 These findings include abrasions or tenderness in the lower chest, abdomen, or pelvis. Other findings mandating CT are the presence of pelvic fractures or thoracolumbar spine fractures. Ultrasound may still have a role in the triage of these patients. Patients with a positive ultrasound should have CT scans performed urgently. Those with a normal ultrasound can have their CT scan performed in a less urgent fashion.
The increased resolution of helical CT allows for the identification of even very subtle injuries, although standard CT is almost always sufficient. CT scans should be performed with intravenous contrast agents in order to differentiate normal parenchyma from blood. Oral contrast agents are extremely helpful in detailing loops of bowel from the mesentery. Rectal contrast agents are virtually never needed for blunt trauma.
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