Chapter 71 Abdominal and pelvic injuries

Although important abdominal injuries are present in only 16–27% of hospital trauma admissions,¹ abdominal and pelvic injuries can represent up to 60% of missed diagnoses in preventable trauma deaths.² Most abdominal and pelvic injuries are caused by blunt trauma; penetrating aetiologies account for 6–21% of cases, depending on the society concerned.^1,³ Important considerations with abdominal and pelvic injuries are:

• difficulties in diagnosing visceral injury

• severity of associated injuries (e.g. chest and head)

• complications, especially sepsis

MECHANISMS OF INJURY

BLUNT INJURIES

Road crashes account for most abdominal and pelvic blunt injuries. Injuries may also result from falls, assaults and industrial accidents.¹ Associated injuries are frequent, involving the thorax (most common), head and extremities. Seat belts and airbags reduce mortality in motor vehicle crashes (mainly by limiting brain injury), but are associated with more lower body injuries. Abdominal and pelvic injuries are more likely with vehicular side-on collisions, and when crashes result in a deformed steering wheel.⁴

PENETRATING INJURIES

Stab and gunshot wounds account for most penetrating injuries to the abdomen.

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of haemodynamically stable patients using investigation algorithms that accurately predict intra-abdominal injury has superseded mandatory laparotomy.⁵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 injury ⁶ carries the risk of missed bowel injury.

INITIAL TREATMENT AND INVESTIGATIONS

RESUSCITATION

Ensuring adequacy of airway, ventilation and oxygenation are immediate priorities. However, circulatory resuscitation should not delay surgery for uncontrolled haemorrhage.⁷ End-points for replacement of blood volume are controversial.⁸ If rapid surgical haemostasis is provided in penetrating trauma, delaying or limiting fluid resuscitation before surgery may improve outcome.⁹ Pneumatic antishock garments provide no benefit.^7,¹⁰

CLINICAL ASSESSMENT

A full clinical examination (including the back) by experienced clinicians is most important. The mechanism of injury may direct attention to particular anatomical areas.⁴

• Contusions, external wounds and their relationship to underlying viscera are noted

• Abdominal distension, tenderness and peritonism are sought but auscultation for bowel sounds is not useful

• The rectum is examined for prostatic position, anal tone, blood or other evidence of injury

• Gastric aspirate and urine are inspected for blood

Isolated penetrating injuries present few diagnostic problems, but the decision to explore the abdomen can be difficult. Blunt abdominal trauma is often part of multiple injuries, and is more difficult to diagnose clinically, except when abdominal signs are obvious.

Nevertheless, in conscious patients, serial assessments can accurately identify those with significant intra-abdominal pathology. In the presence of impaired consciousness,intellectual disability or spinal, chest or pelvic injury, clinical assessment is unreliable. Other more visually spectacular injuries may also divert attention from the abdomen.

Laparotomy is indicated on clinical grounds when there is:

• shock with signs of intra-abdominal haemorrhage (e.g. peritonism or increasing distension)

• evisceration or peritonism without shock in penetrating trauma

In all other situations where clinical examination is inadequate, further investigations must be undertaken.¹¹

PLAIN X-RAYS

A chest X-ray (preferably erect) is essential. It may demonstrate free intraperitoneal gas, herniation of abdominal contents through a ruptured diaphragm, or other abnormalities. Plain films of the abdomen are of no benefit. An anteroposterior pelvic X-ray is indicated for all victims of blunt trauma, except conscious patients with normal pelvis on examination.¹²

INVESTIGATIONS FOR OCCULT ABDOMINAL 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

• FAST is non-invasive, rapid and reasonably accurate when used by trained staff. It can screen for haemoperitoneum but negative studies should be followed by another investigation ^15,¹⁶

• DPL is invasive, takes some time and is accurate in identifying intraperitoneal bleeding or contamination, but may miss diaphragmatic injuries and does not examine the retroperitoneum. It is an alternative to FAST in unstable patients with blunt trauma, and stable patients with anterior stab wounds

• CT is non-invasive, time-consuming, accurate, and has a primary role in defining the location and magnitude of intra-abdominal injuries in stable patients with blunt trauma or penetrating trauma to the flank or back

• FAST, DPL and CT are complementary,²⁴ and should all be available. If CT is unavailable, DPL rather than FAST is indicated in the stable patient with blunt trauma in whom clinical examination is inadequate