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

  • Early operative determination
  • Performed rapidly
  • Can detect bowel injury
  • No need for transport from resuscitation area
  • Early operative determination
  • Noninvasive
  • Performed rapidly
  • Repeatable
  • No need for transport from resuscitation area
  • Anatomic diagnosis
  • Noninvasive
  • Repeatable
  • Visualizes retroperitoneal
  • structures
  • Visualizes bony and soft-tissue
  • structures
  • Visualizes extraluminal air
  • Invasive
  • Risk of procedure-related
  • injury
  • Requires gastric and urinary decompression for prevention of complications
  • Not repeatable
  • Interferes with interpretation
  • of subsequent CT or FAST
  • Low specificity
  • Can miss diaphragm injuries
  • Operator-dependent
  • Bowel gas and subcu-
  • taneous air distort images
  • Can miss diaphragm, bowel,
  • and pancreatic injuries
  • Does not completely assess
  • retroperitoneal structures
  • Does not visualize
  • extraluminal air
  • Body habitus can limit image clarity
  • Higher cost and longer time
  • Radiation and IV contrast exposure
  • Can miss diaphragm injuries
  • Can miss some bowel and pancreatic injuries
  • Requires transport from resuscitation area
  • Abnormal hemodynamics in blunt abdominal trauma
  • Penetrating abdominal trauma without other indications for immediate laparotomy
  • Abnormal hemodynamics in blunt abdominal trauma
  • Penetrating abdominal trauma without other indications for immediate laparotomy
  •  Normal hemodynamics in blunt or penetrating abdominal trauma
  • Penetrating back/flank trauma without other indications for immediate laparotomy