Figure 9.1 (A) Abdominal contents. (B) Gastrointestinal structures. ((A) After Stillwell S (1996). Mosby’s Critical Care Nursing Reference Guide, 2nd edn. St Louis: Mosby; (B) After Seidel HM et al. (1995) Mosby’s Guide to Physical Examination. 3rd edn. St Louis: Mosby.)

Retroperitoneal space

The retroperitoneal space is the area posterior to the peritoneal lining of the abdomen, and contains the abdominal aorta, inferior vena cava, the pancreas, kidneys, adrenal glands, ureters, duodenum, and the posterior aspects of the ascending and descending colon and the retroperitoneal components of the pelvic cavity. Detecting injuries to the retroperitoneal viscera is difficult and may be delayed due to the obscurity of physical examination and the delay in appearance of signs and symptoms of peritonitis. Diagnostic peritoneal lavage does not sample this space and is therefore an unreliable test for injury to this area of the abdomen (Sikka 2004, Emergency Nurses Association 2007, American College of Surgeons 2008).

Pelvic cavity

The pelvic cavity is surrounded by the pelvic bones; it contains the rectum, bladder, urethra, prostate gland, iliac vessels and, in women, internal reproductive organs. Examination of the pelvic structures is compromised by the overlying bony framework.

Mechanism of injury

Many injuries may not manifest during the initial assessment and treatment period, resulting in an undiagnosed or missed injury. The most common errors in the initial assessment of a patient with trauma are an inadequate primary and secondary survey and a low index of suspicion of significant injury. Both of these clinical failures may be attributed to an under-appreciation of and for the mechanism of injury and history of the traumatic episode (Sikka 2004, American College of Surgeons 2008, Weber et al. 2010).

Missed injury is defined as an injury that is not discovered during the initial evaluation and workup in the emergency department (ED) or operating room (Sikka 2004). The incidence of missed traumatic injuries (all injuries) has been broadly estimated to be 1–18 % in the paediatric population and 1–65 % in the adult population. More specifically, missed intra-abdominal injuries are common and carry an additional risk as delays in diagnosis are associated with additional surgery with mortality greater than 50 % (Jansen et al. 2008, Williams et al. 2009, Malinoski et al. 2010).

Intra-abdominal injuries are classically divided into blunt and penetrating trauma and will be described separately.

Blunt abdominal trauma is a leading cause of morbidity and mortality among all age groups (Jansen et al. 2008, Malinoski et al. 2010). Injury to intra-abdominal structures can be classified into two primary mechanisms of injury: compression forces and deceleration forces. Compression or concussive forces may result from direct blows or external compression against a fixed object (lower rim of steering wheel, lap belt, spinal column). Most commonly these crushing forces cause tears and subcapsular haematomas to the solid viscera. These solid viscera, which cannot change shape or stretch, are therefore vulnerable to damage, although they are protected by the thoracic skeleton. When great force is applied, they may be crushed between the lower ribs and the anterior vertebral column or the para-vertebral muscles (American College of Surgeons 2008, Rushings & Britt 2008). Fractures of the lower ribs should create a high level of suspicion of associated visceral damage or diaphragmatic injury (Guitron et al. 2009). Lap-belt marks have been correlated with rupture of small intestine and increased incidence of other intra-abdominal injury (Barry et al. 2003, Rushings & Britt 2008).

Although more commonly injured as a result of penetrating trauma, the pancreas may also be injured by crushing against the anterior spine. These forces may also deform hollow organs and transiently increase intraluminal pressure, resulting in rupture; this is a common mechanism of blunt injury to the small bowel.

Sudden-deceleration injuries may be the result of motor vehicle trauma or falls from a height. The abdominal organs move at the same speed as the external framework of the body. The external framework may decelerate suddenly, as in the case of a car driver hitting the steering wheel, dashboard or windscreen during a high-velocity collision. The driver’s abdominal organs will continue at the pre-collision velocity, putting strain on or disrupting their points of attachment, until they meet another structure such as the abdominal wall.

Deceleration forces cause stretching and linear shearing between relatively fixed and free objects. Longitudinal shearing forces tend to rupture supporting structures at the junction between free and fixed segments (Rushings & Britt 2008). Classic deceleration injuries include hepatic tear along the ligamentum teres, intimal injuries to renal arteries and injuries to the arch of the aorta. Thrombosis and mesenteric tears can occur as a result of loops of bowel travelling from their mesenteric attachments.

Frequency: The true frequency of abdominal injury due to blunt trauma is unknown. According to the American College of Surgeons (2008), in patients undergoing laparotomy for blunt trauma the organs most frequently injured are the spleen (40–55 %), liver (35–45 %) and small intestine (5–10 %). In addition, there is a 15 % incidence of retroperitoneal haematoma in patients undergoing laparotomy for this type of injury.

Review of adult trauma databases in the US reveals that blunt trauma is the leading cause of intra-abdominal injury and that motor vehicle collisions are the leading mode of injury. Blunt injuries account for approximately two-thirds of all injuries, with a male to female ratio of 60:40. Peak incidence occurs in persons aged 14–30 years (Burkitt & Quick 2007, American College of Surgeons 2008).

Penetrating trauma

Throughout history, humans have created easily concealed personal weaponry designed initially for self-defense. Penetrating injuries are caused as a result of stabbing, accidental impalement, or high- or low-velocity projectiles, such as bullets or debris resulting from blast explosions. Each class of instrument or wounding source is associated with a different injury pattern of tissue damage by laceration or cutting. Abdominal organs are vulnerable to penetrating injuries not only through the anterior abdominal wall but also through the back, flank and chest below the fourth intercostal space, which may result in additional penetration of the abdomen through the diaphragm (Emergency Nurses Association 2007, Jurkovich & Wilson 2008).

Stab wounds: Stab wounds traverse adjacent abdominal structures and most commonly involve the liver (40 %), small intestine (30 %), diaphragm (20 %) and colon (15 %) (American College of Surgeons 2008). Only 33 % of stab wounds penetrate the peritoneal envelope, however, and of these peritoneal violations only 50 % require intervention (Barry et al. 2003, Jurkovich & Wilson 2008). Knowledge of anatomic site, number of wounds, and type, size and length of blade will aid in determining the likely path and whether the peritoneum was breached (Fig. 9.2). Lacerated hollow organs result in haemorrhage and leakage of contained fluids into the peritoneal or retroperitoneal space, resulting in poorly defined and localized somatic pain. Pain radiating to the back or shoulder may provide a valuable clue to the presence of intraperitoneal blood, clots or air. Kehr’s sign is described as severe left shoulder pain caused by irritation of the left diaphragm and phrenic nerve, which is induced by laying the patient in a supine position and is indicative of free intra-abdominal blood and clots (Aitken & Niggemeyer 2007). Ecchymosis around the umbilicus (Cullen’s sign) or Grey-Turner’s sign, which is described as a bluish discoloration at the lower abdominal flanks and lower back, may appear with retroperitoneal bleeding originating in the kidney or with pelvic fractures. These signs may occur some hours or even days after initial injury but may be observed during nursing assessment in the ED (Aitken & Niggemeyer 2007, Bacidore 2010, Blank-Reid & Reid 2010).

Figure 9.2 Path of knife blade penetration in patient. (After McSwain N (2003). The Basic EMT: Comprehensive Prehospital Patient Care. 2^nd Edn. St Louis: Mosby.)

Gunshot injury: Gunshot injuries to the abdomen involve high energies and may damage organs remote from the site of penetration into the abdomen. It is important to establish the type of weapon used, whether handgun, shotgun or rifle, and the distance between the patient and the gun. Gunpowder around the bullet entry site will suggest firing at close range and is usually associated with an increase in injury severity. Up to 95 % of gunshot wounds to the abdomen result in visceral injury and require a surgical procedure (Feliciano et al. 2008). The amount of energy released is proportional to the mass and velocity of the bullet and also depends on the density of tissue involved. A low-velocity bullet from a handgun will release less energy and cause less injury than a high-velocity bullet from a rifle. Similarly, a high-mass bullet will cause more damage than a low-mass bullet of similar velocity. An accurate history involving the type of weapon used and the range at which it was fired is essential in order to assess the likely magnitude of visceral injury (American College of Surgeons 2008).

A bullet will release its energy in the abdomen in two ways: first, by direct contact with organs in its path. Bullets may take a non-linear path through the abdomen. A simple, straight line connecting entry and exit wounds may not indicate the actual path of the bullet. In cases where there is no exit wound, X-rays will locate the bullet. Second, bullets transfer energy in the form of pressure waves. These pressure waves may disrupt many organs not in the actual path of the bullet. Pressure waves result in cavitation, extending the diameter of injury to many times the actual diameter of the bullet. A low-velocity missile, from a gun travelling at 1000–3000 ft/s, creates a cavity 2–3 times the diameter of the missile (Feliciano et al. 2008). High-velocity missiles, i.e., those travelling at more than 3000 ft/s, create a cavity that may be 30–40 times the diameter of the bullet (Dickinson 2004, Blank-Reid & Reid 2010) (Fig. 9.3).

Figure 9.3 Potential injury path of high- and low-velocity bullets. (After Neff JA, Kidd PS (1993). Trauma Nursing: the Art and Science. St Louis: Mosby.)

Dense, solid viscera are more susceptible to cavitation than hollow organs. The sudden formation of a cavity increases intra-abdominal volume, creating a negative pressure, which may suck debris, such as clothing in through the entry wound resulting in gross intra-abdominal contamination. Gunshot wounds most commonly involve the small bowel (50 %), colon (40 %), liver (30 %), and abdominal vascular structures (25 %) (Barry et al. 2003, American College of Surgeons 2008).

Frequency: The frequency of penetrating abdominal injury across the globe relates to the industrialization of developing nations and, significantly, to the presence of military conflicts. The death rate from penetrating abdominal trauma spans the entire spectrum (0–100 %), depending on the extent of injury. Patients with violation of the anterior abdominal wall fascia without peritoneal injury have a 0% mortality and morbidity rate. An average mortality rate for all patients with penetrating abdominal trauma is approximately 5 % (Barry et al. 2003, Burkitt & Quick 2007).

Blast injuries

In general, most blast injuries managed in EDs tend to be accidental. They include firework mishaps, unintended occupational or industrial fuel eruptions, and unforeseen mine explosions. In many parts of the world, however, the reality persists of deadly, dormant, non-detonated, military incendiary devices such as land mines and hand grenades. Such devices cause significant numbers of civilian casualties years after local hostilities cease. During wartime, injuries arising from explosions frequently outnumber those from gunshots; many victims are innocent civilians. Blast injuries caused by terrorist bombings are also a growing part of the landscape in which people now live their lives.

The sudden, massive and catastrophic changes of pressure associated with blasts or explosions may damage the air-filled ‘hollow’ viscera of the gastrointestinal tract. The air within the viscera will transmit the force of the blast equally in all directions, leading to a general disruption or ‘bursting’ effect (Fig. 9.4).

Figure 9.4 Effects of an explosive blast. (From ENA & Newberry: Sheehy’s Emergency Nursing: Principles and Practice, 5^th edn, Mosby 2002, with permission.)

Mannion & Chaloner (2005) categorize blast injuries into four categories: primary, secondary, tertiary, and quaternary. A patient may be injured by more than one of these mechanisms.

• Primary blast injury is caused solely by the direct effect of blast overpressure on tissue. Air is easily compressible, unlike water. As a result, a primary blast injury almost always affects air-filled structures such as the lung, middle ear and gastrointestinal (GI) tract. Other injuries include rupture of the eye and concussion without signs of head injury.

• Secondary blast injury is caused by flying objects that strike people. Injuries include penetrating ballistic or blunt injuries and eye penetration that can be occult.

• Tertiary blast injury is a feature of high-energy explosions. This type of injury occurs when people fly through the air and hit fixed objects such as walls. Fracture and traumatic amputations and closed and open brain injury are common with tertiary blast injuries.

• Quaternary blast-related injuries encompass all other injuries caused by explosions. For example, the collision of two jet airplanes into the World Trade Center on 11 September 2001 created a relatively low-order pressure wave, but the resulting fire and building collapse killed thousands (Arnold et al. 2004). The range of injuries from quaternary blasts includes flash, partial and full-thickness burns, crush injuries, closed and open brain injury, asthma or other breathing-related problems from dust, smoke or toxic fumes, angina, hyperglycaemia, hypertension, etc. (Taylor & Dawood 2005).

Frequency: Internationally, the incidence of blast injury is sporadic and infrequent and is dependent on the political (terrorism, occupational health and safety priorities) stability of the region. Mortality rates vary widely and are increased when explosions occur in closed or confined spaces (Owers et al. 2011). The presence of tympanic membrane rupture indicates that a high-pressure wave (at least 40 kPa, 6 psi) was present and may correlate with more dangerous organ injury. Table 9.1 provides an overview of explosion-related injuries.

Table 9.1

Overview of explosion-related injuries

System	Injury or condition
Auditory	Tympanic membrane rupture, ossicular disruption, cochlear damage, foreign body
Eye, orbit, face	Perforated globe, foreign body, air embolism
Respiratory	‘Blast lung’, haemothorax, pneumothorax, pulmonary contusion or haemorrhage, arteriovenous fistulae acting as sources of air embolism, airway epithelial damage, aspiration, pneumonitis sepsis
Digestive	Bowel perforation, haemorrhage, ruptured liver or spleen, sepsis, mesenteric ischaemia from air embolism
Circulatory	Cardiac contusion, myocardial infarction from air embolism, shock, vasovagal hypotension, peripheral vascular injury, air-embolism-induced injury
Central nervous injury	Concussion, closed and open brain injury, stroke, spinal cord injury, air-embolism-induced injury
Renal	Renal contusion or laceration, acute renal failure due to rhabdomylosis, hypotension, hypovolaemia
Extremities	Traumatic amputation, fractures, crush injuries, compartment syndrome, burns, cuts, lacerations, acute arterial occlusion, air-embolism-induced injury

(After Taylor I, Dawood M (2005) Terrorism: the reality of blast injuries. Emergency Nurse, 13(8), 22–25; Centers for Disease Control (CDC) (2003) Explosions and Blast Injuries: A Primer for Clinicians. Atlanta: CDC.)