STAB AND LACERATION WOUNDS

Entry sites do not accurately predict the nature of deeper injury. Penetration of the thoracic cavity should be suspected with upper abdominal wounds; conversely, lower chest wounds may involve abdominal structures. Selective management of haemodynamically stable patients using investigation algorithms that accurately predict intra-abdominal injury has superseded mandatory laparotomy.⁵

GUNSHOT WOUNDS

Injuries depend on missile calibre, and its velocity and trajectory. Intra-abdominal, thoracic and multiple organ injuries and mortality are substantially greater than with stab wounds. Laparotomy should be performed in all cases with haemodynamic instability, peritonitis or a clinically unevaluable abdomen. A non-operative approach for solid organ injury⁶ carries the risk of missed bowel injury.

ULTRASONOGRAPHY

Focused abdominal sonography for trauma (FAST) can be performed rapidly in the resuscitation room without compromising ongoing treatment. It requires significant training to achieve acceptable accuracy,¹³ and although highly specific, its sensitivity of around 85%¹⁴ is less than that of peritoneal lavage or CT in detecting free intra-abdominal fluid following either blunt^15,16 or penetrating¹⁷ trauma. FAST can also identify pericardial fluid, but not hollow viscus injury or the nature of solid organ injury.¹⁶ FAST may reduce the need for other investigations,¹⁸ but the small but important false-negative rate must be considered in determining its role in abdominal assessment algorithms.

PERITONEAL LAVAGE

Diagnostic peritoneal lavage (DPL)¹⁹ is indicated in blunt trauma when there is haemodynamic instability or uncertain clinical findings, and in penetrating trauma when peritoneal breach is suspected.

Open and closed (percutaneous guidewire) methods are both satisfactory.²⁰

DPL is unjustified when an indication for laparotomy already exists. It is relatively contraindicated in pregnancy, significant obesity and previous abdominal surgery.

If required in these situations (or with pelvic fractures), the supraumbilical open method should be considered. DPL undertaken early remains reliable in the presence of pelvic fractures.²¹ DPL detects intraperitoneal injury with up to 98% accuracy,¹⁹ but its high sensitivity can result in a significant non-therapeutic laparotomy rate. Cell counts of lavage effluent are more accurate than qualitative methods, but hollow viscus injury is difficult to detect. Generally accepted criteria for a positive DPL are shown in Table 71.1.

Table 71.1 Criteria for positive diagnostic peritoneal lavage

Clinical

Initial aspiration of >10 ml frank blood Egress of lavage fluid via chest tube or urinary catheter Bile or vegetable material in lavage fluid

Laboratory   Blunt injury Penetrating injury Red cells Definite > 100 × 10⁹/l > 20 × 10⁹/l Indeterminate 50–100 × 10⁹/l 5–20 × 10⁹/l White cells 0.5 × 10⁹/l > 0.5 ×10⁹/l Amylase > 20 IU/l > 20 IU/l Alkaline phosphatase > 10 IU/l > 10 IU/l

COMPUTED TOMOGRAPHY (CT)

CT requires a still patient, a high-resolution scanner and experienced interpretation to match the sensitivity of peritoneal lavage. The value of enteral contrast is controversial.²² Cuts from the top of the diaphragm to the symphysis pubis following i.v. contrast are required. CT is particularly useful to assess the retroperitoneum and pelvic fractures, and to delineate the nature of abdominal injury (thus guiding non-operative management of some solid organ injuries). It may not detect all hollow viscus trauma, but multidetector row CT is more specific and sensitive for bowel injury.²³ Magnetic resonance imaging offers no advantage over CT in evaluating acute abdominal trauma, and poses significant logistical problems.

The safety of undertaking CT in acute trauma depends on the degree of cardiorespiratory stability relative to the speed of scanning and access to resuscitation support.

CHOICE OF INVESTIGATION