Diagnostic tools

Focused Abdominal Sonography for Trauma (FAST)

Focused abdominal sonography for trauma (FAST) enables detection of intraperitoneal free fluid in the abdomen in the resuscitation room (Fig 1).

There is evidence to support the accurate delivery of this investigation by appropriately trained emergency physicians.

It is a good predictor of significant intraperitoneal injury if free fluid is detected. However, it does not reliably rule out significant injury if the test is negative. Further assessment and investigation or repeat FAST scan is warranted in this case.

Fig 1 FAST scan showing fluid between the liver and left kidney

Computerised Tomography (CT)

In a physiologically normal patient, computerised tomography (CT) will provide detailed and organ-specific imaging of any intra-abdominal injury (Fig 1). It is more reliable at detecting solid organ injuries and can determine the requirement for operative management. 

Note: Hollow viscus injuries may be missed if oral or intravenous contrast is not used.

Fig 2 CT scan confirming left renal fracture

Diagnostic Peritoneal Lavage (DPL)

Diagnostic peritoneal lavage (DPL) is carried out via a lower midline incision and a litre of normal saline is instilled into the peritoneal cavity. It is allowed to drain out passively and then inspected for blood and contamination. The only contraindication is a need for laparotomy.

This investigation is rarely performed in UK practice with the increasing availability of FAST and CT scanning.

Comparison of Tools

When selecting a definitive investigation, the advantages and disadvantages of each tool should be considered (Table 1) so that the safest and most appropriate investigation for that patient is selected.

It is important to have a lower threshold for investigating any patient who has a significant or high-risk mechanism of injury. For example, a high-speed motor vehicle collision or a fall from a height.

Table 1 Comparison of DPL, FAST, and CT scan in abdominal trauma