Role of US in the diagnosis of intraabdominal catastrophes

Free Fluid Accumulation following Blunt Abdominal Trauma: Potential for Expansion of the Fast Protocol

Objective

To determine sites of free intra-peritoneal fluid collection following blunt abdominal trauma, with a view to refinement of the Focused Assessment by Sonography for Trauma (FAST) protocol.

Methods

This was a retrospective observational study of CT scans of subjects who had suffered blunt abdominal trauma and had free intra-peritoneal fluid detected on CT scan within 24 hours. The depth from the skin and amount of fluid at 14 abdominal sites were determined.

Results

CT scans of 105 patients were examined: 68 (64.8%) were male, mean age 36.7±18.4 years, mean injury severity score 25.4±11.6. Fluid collected most commonly at three sites: right mid-axillary line at the level of the xiphisternum (52 patients, 49.5%), lateral margin of the right rectus muscle at the level of the anterior superior iliac spine (49 patients, 46.7%) and right mid-axillary line at the level of the umbilicus (40 patients, 38.1%). Mean depth of fluid at these sites were 3.6, 3.6 and 4.2 cm, respectively.

Conclusions

Free fluid collects commonly in the area of the right iliac fossa following blunt abdominal trauma. The inclusion of this site in the FAST protocol may increase the ultrasonographic detection of free fluid in the acute trauma setting.

Focused abdominal sonography for trauma in the emergency department for blunt abdominal trauma

BACKGROUND

Blunt abdominal trauma (BAT) is a diagnostic challenge to the emergency physician (EP). The introduction of bedside ultrasound provides another diagnostic tool for the EP to detect intra-abdominal injuries.

AIMS

To evaluate the performance of EP in a local emergency department in Hong Kong to perform the 'focused abdominal sonography for trauma' (FAST) in BAT patients.

METHODS

This was a retrospective cohort study including all the trauma team cases in a 36-month period in the emergency department of a public hospital in Hong Kong. The results of FAST scans were analyzed and compared with CT scans when the FAST was positive or followed by a period of clinical observation when the FAST was negative. Descriptive statistics and sensitivity, specificity, and predictive values were calculated.

RESULTS

There was a total of 273 cases, and FAST scans were performed in 242 cases. The sensitivity and specificity were 86% and 99%, respectively. The negative predictive value was 0.98, while the positive predictive value was 0.94. The overall accuracy was 97%.

CONCLUSIONS

The performance of the EP in using FAST scans in BAT patients was encouraging. The high specificity (99%), positive predictive value (0.98), and likelihood ratio for positive tests (86) make it a good 'rule in' tool for BAT patients. The high negative predictive value also makes the FAST scan a useful screening tool. However, ultrasound examination is operator dependent, and FAST scan has its own limitations. For negative FAST scan cases, we recommend a period of monitoring, serial FAST scans, or further investigations, such as CT scan or peritoneal lavage.

Screening US and CT for blunt abdominal trauma: a retrospective study

OBJECTIVE

To assess the accuracy of screening US and CT in patients with blunt abdominal trauma admitted to the trauma centre of our General Hospital.

MATERIALS AND METHOD

The abdominal US reports of 864 primary trauma patients (139 with major and 725 with minor injuries) and 162 CT reports of a subgroup of the same subjects (64 with major and 98 with minor injuries) were reviewed and compared to the best available reference standard. The accuracy of screening US was assessed by evaluating its overall ability to distinguish negative from positive cases by showing at least one of the lesions documented by the reference standard and its specific ability to depict all lesions; CT reports were evaluated only for the method's performance in depicting all lesions.

RESULTS

Screening US exhibited a satisfactory overall ability to distinguish negative from positive patients (91.5% sensitivity and 97.5% specificity in major trauma patients versus 73.3% sensitivity and 98.1% specificity in the minor trauma group) and a satisfactory specific ability to depict all injuries in major trauma patients. In minor trauma cases sensitivity was satisfactory for free fluid but unsatisfactory for organ injuries. Of the 21/864 false negative reports (5 in patients with major and 16 in cases with minor traumas), only one affected patient management, a major trauma case, by delaying an emergency laparotomy. The performance of CT in detecting each single lesion was predictably excellent in both patient groups.

CONCLUSION

Its satisfactory accuracy for major trauma suggests that US could be employed not only to screen cases for emergency laparotomy but also as an alternative to CT. However, since major traumatic injuries generally carry an imperative indication for CT, especially as regards neurological, thoracic and skeletal evaluation, US should be employed to perform a prompt preliminary examination using a simplified technique in the emergency room simultaneously with resuscitation.