Abdominal trauma occurs frequently, and the presentation, evaluation, and treatment of damage to the intra-abdominal viscera are established. Isolated abdominal wall trauma is much less common and is rarely even considered in the initial assessment of the patient unless obvious signs are present. It is most commonly associated with musculoskeletal, head, or thoracoabdominal trauma, and its significance is, among other things, as a herald of underlying pathology.

The aetiology depends on the demographics of the society and the environment, and includes blunt trauma (motor vehicle accident, pedestrian struck by a motor vehicle, motorcycle or bicycle accidents, falls), penetrating injuries (stab wounds, gunshot wounds), and blast injuries that have become common in some areas of the world.

Blunt forces that result from motor vehicle accidents vary depending upon the location of the accident, abuse of alcohol, and use of seatbelts. The incidence of penetrating injuries increase in an urban environment, and these are commonly associated with illicit drug use. The injuries that follow bombing or explosions caused by warfare or terrorist activity are rare, but such injuries may also occur in civilian locations such as mines, shipyards, and chemical plants. Flying glass, mortar, or other debris from the blast will have a penetrating force and the victim may become a projectile and suffer acceleration/deceleration forces when the abdomen strikes immobile objects.

The abdominal wall trauma that results from penetrating forces is usually obvious: stab wounds result in lacerations of the skin and subcutaneous tissue with deeper injuries causing lacerations of the muscle, fascia, and perhaps peritoneum. The effects of gunshot wounds vary, depending upon the calibre and velocity of the missile, but the kinetic energy generated causes major abdominal wall defects as the projectile passes through the tissue. In blunt trauma, the sudden application of a large force to the contracted abdominal wall musculature over a fulcrum is similar to the force that is responsible for diaphragmatic disruptions. The ‘seatbelt syndrome’ resulting from an improperly positioned lap belt is well recognized. The force can disrupt the body of the rectus abdominous muscle, as well as the external and internal oblique muscles, or cause an avulsion of the abdominal musculature from the costophrenic arch or pubis. Uniquely associated with the seatbelt syndrome is a fracture of the posterior process and/or the body of the lumbar spine. This was described by Chance in 1948 (and the fracture now bears his name) and results from hyperflexion of the spine about a fixed axis anterior to the vertebral column. These flexion/distraction fractures are often associated with the ‘seatbelt sign’ (Fig. 1) 1346. The injury is thought to arise from flexion over a fulcrum (the lap belt) causing distraction of the posterior elements of the spine.

Associated injuries to the head, thoracic, and extremity injuries often occupy the diagnostic and therapeutic attention. Clinical evidence of an abdominal wall injury may be obvious, with evisceration after a penetrating wound (Fig. 2) 1347 or a contusion from an improperly applied seatbelt (‘seatbelt sign’). These should warn the physician of potential intra-abdominal injuries. The patient may complain of localized abdominal wall pain and a defect in the fascia may be palpated. There is often an abdominal wall mass.

The pathology seen depends on aetiology and includes lacerations of the abdominal wall skin, subcutaneous tissue, fascia, and muscles, following penetrating injuries, or contusions, haematoma formation, disruption of subcutaneous fat and abdominal wall muscle, and herniation from blunt forces. Traumatic hernia of the abdominal wall has a specific diagnostic triad: immediate appearance of a hernia with intact skin after blunt abdominal trauma, signs of injury at the time of the initial medical evaluation, and no identifiable hernial sac at exploration.

Intra-abdominal viscera are injured in 30 to 50 per cent of patients suffering abdominal wall trauma. The blunt forces involved cause a sudden increase in intra-abdominal and intraluminal pressure, with disruption of hollow viscuses; shearing forces may damage the mesentery (Fig. 3) 1348.

Diagnostic efforts are usually focused on the underlying intra-abdominal visceral injury. CT scan may reveal an abdominal wall defect with extrusion of small bowel. The hernia may present as an easily palpable anterior abdominal mass, but only become apparent during exploration of the abdomen.

The management of abdominal wall injuries should be a secondary consideration in the majority of patients. The evaluation and management of their associated and perhaps life-threatening injuries should be first priority.

Abdominal hernias should be repaired at the time of presentation, and this can normally be accomplished using non-absorbable suture (polypropylene, nylon). Rarely, the defect may be large and require a prosthetic graft to effect closure. The latter are normally hernias which have been neglected due to a delay in diagnosis. Injuries that result in tissue necrosis and significant contamination create enormous management problems and are fortunately rare. Contamination is a relative contraindication to the use of prosthetic material in closure of the abdominal wall, but this may be unavoidable.

Intra-abdominal visceral injuries are repaired, necrotic tissue is debrided, and the wound is vigorously irrigated. Appropriate antibiotics should be administered. If prosthetic grafts are required polytetrafluoroethylene has been successfully used and is reportedly resistant to infection.

Gunshot or shotgun wounds require local debridement, and large defects may be created as a result of tissue distribution. The defect should be required either primarily or as described for blunt trauma.

Sharp injuries to the abdominal wall are relatively simple to treat, with debridement of necrotic tissue and primary closure of the fascial edges. Polypropylene or nylon are an ideal closure material; drains are rarely indicated.

Injuries to the abdominal wall are low on the list of priorities in the management of the patient with abdominal trauma. Local symptoms may make their presence more obvious, as will evisceration. Primary early repair is the ideal method of management. The presence of abdominal wall trauma should serve as a marker to alert the physician to the potential of injuries to the intra-abdominal viscera.