FAST scan: is it worth doing in hemodynamically stable blunt trauma patients?

Background: During the last decade, focused assessment with sonography for trauma increasingly has become the initial diagnostic modality of choice in trauma patients. It is still questionable, however, whether its use results in the underdiagnosis of intra-abdominal injury. It also remains doubtful whether a positive focused assessment with sonography for trauma affects clinical decision making in hemodynamically stable blunt trauma patients as evidenced through abdominal computerized tomography use. The aim of this study was to evaluate the results of focused assessment with sonography for trauma in hemodynamically stable blunt trauma patients and to determine its role in the diagnostic evaluation of these patients.

Methods: We reviewed our prospectively maintained trauma database. In trauma patients at our institute, focused assessment with sonography for trauma examinations are performed by surgery residents and are considered positive when free intra-abdominal fluid is visualized. Abdominal computerized tomography, diagnostic peritoneal lavage, or exploratory laparotomy findings were used as confirmation of intra-abdominal injury.

Results: In our 7-year study period, 2,980 trauma patients were evaluated at our institute, of which 2,130 patients underwent a focused assessment with sonography for trauma. In all, 18 patients had an inconclusive focused assessment with sonography for trauma, whereas 7 patients died on arrival, leaving 2,105 patients for our analysis. A total 88 true positive focused assessment with sonography for trauma were conducted. All hemodynamically stable blunt trauma patients who had a positive focused assessment with sonography for trauma (70/88) were confirmed by computerized tomography. Patients who underwent exploratory laparotomy directly (17/88) or diagnostic peritoneal lavage (1/88) as confirmation either had penetrating trauma or became hemodynamically unstable. A total of 1,894 true negative focused assessments with sonography for trauma scans were conducted, with 1,201 confirmed by computerized tomography and the rest by observation. In all, 118 false negative focused assessment with sonography for trauma were performed, of which 44 (37.3%) subsequently required exploratory laparotomy. Five patients had false positive focused assessment with sonography for trauma scans. Focused assessment with sonography for trauma scan had an overall sensitivity of 43%, a specificity of 99%, and positive and negative predictive values of 95% and 94%, respectively. Accuracy was 94.1%. In the hemodynamically stable blunt trauma group, there were 60 patients with true positive focused assessment with sonography for trauma examinations and 87 patients with false negative focused assessment with sonography for trauma examinations. In this group of patients, focused assessment with sonography for trauma had a sensitivity of 41%, specificity of 99%, and positive and negative predictive values of 94% and 95%, respectively. The overall accuracy was 95%.

Conclusion: Given the low sensitivity, a negative focused assessment with sonography for trauma without confirmation by computerized tomography may result in missed intra-abdominal injuries. It is also observed in all focused assessment with sonography for trauma positive hemodynamically stable blunt trauma patients, confirmation is preferred through the use of a computerized tomography for better understanding of the intra-abdominal injuries and to decide on operative versus no-operative management. Thus, the use of focused assessment with sonography for trauma in hemodynamically stable blunt trauma patients seems not worthwhile. It should be reserved for hemodynamically unstable patients with blunt trauma.