Stab Wounds.: Knives are not the sole implements used in stabbings. Ice picks, pens, coat hangers, screwdrivers, and broken bottles, to name a few, have been used by assailants. Stab wounds of the abdomen occur most commonly in the upper quadrants, the left more commonly than the right. They are multiple in 20% of cases and involve the chest in up to 10% of cases. Most stab wounds do not cause an intraperitoneal injury, and the incidence varies with the direction of entry into the peritoneal cavity. Anterior stab wounds penetrate the peritoneum in approximately 70% of cases but inflict a visceral injury in only half of these.⁴ Left lower chest wounds are associated with a 17% incidence of intraperitoneal damage in addition to the expected high rate of thoracic and diaphragmatic injuries. Right lower chest wounds have a much lower incidence of 0% to 4%.¹² Abdominal entries from the flank and back have reported incidences of up to 44% and 15%, respectively.^13,14 The organ injured cannot be well predicted by the site of entry in the abdominal wall. The liver and spleen are the viscera most commonly damaged in cases of back and flank wounds.

Gunshot Wounds—Ballistics.: The science of ballistics is complex, but a few basic principles are helpful in understanding the pathophysiologic processes of these injuries. The magnitude of the injury is proportional to the amount of kinetic energy imparted by the bullet to the victim, according to the following equation:

where E is the kinetic energy (in foot-pounds), m is the mass of the bullet, v is the velocity of the bullet (in ft/s), and g is gravitational acceleration (in ft/s). In other words, the degree of injury depends on the mass of the bullet and the square of its velocity.¹⁵ Additional factors that affect injury created by a missile include the resistance and viscoelastic properties of the tissue through which it passes, as well as the stability of the missile in this medium. Missile velocities are categorized as low (slower than 1100 ft/s), medium (1100-2000 ft/s), and high (faster than 2000-2500 ft/s); the impact velocity is the most important determinant of wounding capability. The impact velocity depends on the distance between the firearm and the victim, the muzzle velocity, and various characteristics of the missile. At medium and high velocities, the missile has an explosive effect and creates a temporary passage in the tissue along its course. The size of this passage is directly proportional to the specific gravity of the penetrated tissue. This sudden formation of a tract displaces nearby organs and vascular structures, and bone and viscera may be fractured or torn without being directly struck by the missile. Several cases of an intraperitoneal injury caused by a bullet that remained extraperitoneal throughout its entire course have been reported.¹⁶ Solid viscera, such as the liver and spleen, are more vulnerable to this effect.

High-Velocity Missiles.: Wounds from high-velocity missiles involve additional problems. First, external contaminants tend to be dragged into the wound. Second, the closure of the tract immediately after the bullet’s passage may lead to an underestimation of tissue damage. Finally, high-velocity bullets can fragment internally. In fact, a missile at any velocity can fragment after contact with bone and cause additional multiple trajectories and injuries. Civilian wounds have usually resulted from low-velocity handguns, but unfortunately a trend toward more destructive weapons, such as the .38 and .357, may be occurring.

Shotgun Wounds.: The shotgun was designed to strike a small, fast-moving target at close range. Because of the ballistic shape of the individual pellets, a rapid falloff in velocity occurs, making this weapon ineffective in producing severe wounds at long distances. An initial muzzle velocity of 1300 ft/s drops to 950 ft/s within 20 yards, a decrease of 25%. At close range (<15 yards), however, the shotgun is extremely lethal.

The kinetic energy imparted to the victim depends on the pellet’s size, the number of striking pellets, the type and amount of powder, and the barrel choke (constriction). The most important variable is the distance between the shotgun and the victim. At a distance of 10 yards, 19% of the pellets cluster in a 9-inch diameter circle if fired from a full choke (maximum constriction) barrel. At a distance of 20 yards, the circle is approximately double that diameter. Because the kinetic energy is proportional to the square of the velocity, a 25% loss of velocity at 20 yards results in a significant decrease in the damage produced by the blast.

Shotgun wounds have been previously classified in three groups according to the range and pattern of distribution. More recently, classification has been according to the pattern of injury on the victim. Based on distance from the weapon to the victim, type I wounds involve a long range (>7 yards) and a penetration of subcutaneous tissue and deep fascia only. Type II wounds occur at a distance of 3 to 7 yards and may create a large number of perforated structures. Type III wounds occur at point-blank range (<3 yards) and involve a massive destruction of tissue. When categorized by pattern, type I wounds produce a spread greater than 25 cm in diameter; type II, 10 to 25 cm in diameter; and type III, less than 10 cm in diameter.¹⁷ The tissue damage is proportional to the specific gravity and inversely proportional to the elastic properties of the affected organ. Thus the liver is more vulnerable than the lungs to this injury. Close-range shotgun wounds, in addition to the shot, force external contaminants (e.g., clothing and parts of the shell wadding) into the wounds. Type III wounds carry a substantial mortality risk.

Seatbelt Injuries.: Unrestrained front and rear seat passengers are at unequivocally greater risk of intra-abdominal injury than their restrained counterparts.¹⁸ The three-point shoulder-lap belt is the most effective restraining system and is associated with the lowest incidence of abdominal injuries, compared with older systems. However, abdominal injuries are still ascribed to combined shoulder-lap and lap-belt systems. The shoulder belt component can lead to right-sided and left-sided rib fractures for the driver and front seat passenger, respectively, with potential for injury to underlying abdominal viscera. Improper underarm usage of the shoulder belt increases compressive forces to the upper abdomen, particularly in the event of a front-end crash.

Injuries resulting from solitary lap belts are most often to the abdomen. This is true of nearly half the injuries caused by lap belts. The pathogenesis is usually the compression of bowel between the belt and the vertebral column. Occasionally, an acute, short, closed-loop obstruction occurs along with perforation secondary to the sudden generation of high intraluminal pressures. The resultant injury is primarily a contusion or perforation of the intestines or a tear of the mesentery.

Clinically, two symptom patterns emerge. Approximately one fourth of these patients develop evidence of a hemoperitoneum secondary to mesenteric lacerations. In the remainder, the intestinal injury most commonly involves the jejunum, and the initial signs and symptoms are often absent or considered insignificant. Subsequent delays in diagnosis of up to 8 weeks have rarely been reported. The “seatbelt sign,” contusion or abrasion across the lower abdomen, is found in less than one third of patients with abdominal injuries caused by lap belts. Its presence, however, is highly correlated with intraperitoneal pathologic lesions.¹⁹ Rupture of the diaphragm can also occur. Rare cases of acute abdominal aortic dissection with incomplete or complete occlusion have also been described, and injuries to the lumbar spine are not uncommon.²⁰

Iatrogenic Injuries.: Although well intentioned, diagnostic and therapeutic efforts in patient care are not risk-free. Abdominal injuries may be sequelae of various medical procedures and in certain instances not only are extremely difficult to recognize but may contribute to or cause pronounced morbidity or death. Numerous procedures may cause an iatrogenic injury.

Artificial ventilation can lead to gastric distention, particularly in children. Besides compromising ventilation and increasing the risk of vomiting and aspiration, a significant distention may lead to an esophageal or gastric laceration and perforation. These may occur with bag-mask ventilations, an inadvertent esophageal intubation with a nasotracheal or endotracheal tube, or the mistaken connection of the nasogastric tube to oxygen rather than suction. Esophageal, gastroesophageal junction, and gastric lacerations are evidenced by bloody emesis or nasogastric return. If a gastric perforation occurs and positive-pressure breathing is maintained, a tension pneumoperitoneum or abdominal compartment syndrome may ensue with inferior vena cava compression and decreased cardiac output. External cardiac compressions have produced splenic, hepatic, and gastric injuries. Manual thrusts to clear an airway obstruction, as taught in basic life support courses, and the Heimlich maneuver have caused rib fractures with lacerations and the rupture of abdominal viscera. In cases of a cardiac arrest, these injuries may be occult but life-threatening. If hypotension occurs after cardiopulmonary resuscitation, an abdominal injury and hemorrhage are considered along with cardiogenic shock.²¹

Tube thoracostomy has resulted in injury to the liver and spleen. These injuries may result from an unrecognized elevation of the diaphragm on the side of the thoracostomy or the placement of the tube too low in the chest, with resulting intra-abdominal penetration. Peritoneal lavage, paracentesis, and peritoneal dialysis have caused a series of complications, especially vascular penetration and bowel perforation. Signs of blood loss from a hemoperitoneum in the former case and peritonitis in the latter will evolve.

A liver biopsy can lead to a hemoperitoneum or hemobilia. Endoscopic procedures of the bowel may cause a hollow viscus perforation and peritonitis, particularly when a biopsy is performed, although they can result from rapid retraction of the endoscope without biopsy, as well.²² Peritoneoscopy has been reported to cause small bowel perforations and iliac vessel lacerations. Barium enemas have an extremely low incidence of perforation but can be another cause of unexplained peritonitis and pneumoperitoneum.

Pediatrics.: Congenital anomalies and intra-abdominal neoplasms may be first discovered after a history of blunt trauma. Coagulopathies (e.g., hemophilia) can contribute to the pathologic condition and complicate therapy after apparent minor trauma to the abdomen.

A child’s abdomen has poorly developed musculature and a relatively smaller anteroposterior diameter. These factors increase the vulnerability of abdominal contents to compression between a blunt anterior force and the solid posterior vertebrae. The rib cage is extremely compliant in children and less prone to fractures but nonetheless provides only partial protection against splenic and hepatic injuries. Finally, the bladder is less protected by the pelvis in children, exposing it to greater risk of injury.

The liver, spleen, and kidney are the organs most commonly damaged by blunt mechanism of all varieties, and the incidence of injury for each of these three solid viscera is roughly the same. Gastrointestinal tract perforation is not uncommon with blunt trauma, and these injuries may be isolated. In cases of nonaccidental trauma, those injuries seen most commonly are duodenal and small bowel hematomas and perforations, pancreatic contusions, lacerations and pseudocysts, lacerations and rupture of the liver and spleen, and lacerations of mesenteric vessels.

Stab Wounds.: It is helpful to obtain information regarding the mode of injury from the patient, paramedic, or witnesses. The number of stabs inflicted, type and size of the instrument, posture of the victim relative to the direction of assault, estimated blood loss at the scene, time of injury, and response to fluids should be sought. However, a significant proportion of victims of stab wounds are found under the influence of alcohol or another drug. This state can make obtaining an accurate history a futile effort and further compromises the validity of symptoms and signs.

Gunshot Wounds.: As initial stabilization measures are instituted in the emergency department, the emergency physician can elicit certain facts that can contribute greatly to the evaluation of the patient. These include the weapon used, its distance from the victim when shot, the position of the victim in relationship to the weapon when fired, the suspected number of shots, the blood loss at the scene, the amount and type of field fluids administered, and the vital signs during the prehospital course.

Stab Wounds.: Serial physical examinations performed by the same observer are gaining acceptance in certain centers where these have been found useful, particularly with patients who are alert, communicative, and neurologically intact. The presence of intoxicants does not necessarily preclude reliance on examination but may undermine its value.³⁰ In other series, patients with impressive physical findings after penetrating trauma to the abdomen have undergone exploratory laparotomy, with negative results in 14 to 28% of cases.³¹ Moreover, up to one third of patients with significant intra-abdominal injuries have no suggestive physical signs, particularly when a retroperitoneal injury has occurred.³² Therefore serial clinical evaluations typically involve physical examinations to include trending of vital signs, laboratory testing including serial hemoglobin measurement, and repeated focused assessment with sonography in trauma (FAST) examinations.

Gunshot Wounds.: As with blunt or other modes of penetrating trauma, there is dispute regarding the value of the physical examination of patients with abdominal GSWs. In various series, 20% of patients with a documented intraperitoneal injury had no peritoneal signs before exploration.³² Moreover, objective physical findings suggestive of intra-abdominal damage have been misleading and falsely positive in 15% of patients in whom laparotomy revealed no injury. Other authors contend that selective management can be undertaken safely when physical examination is the fundamental evaluative measure.³⁰

Hematocrit.: The hematocrit reflects baseline value, extent of and time from hemorrhage, exogenous fluid administration, and endogenous plasma refill. The last of these is a physiologic compensatory shift of extracellular fluid into the intravascular space, the intent of which is to restore the original blood volume. Based on a study of volunteers sustaining a 10 to 20% blood loss, this restoration proceeds at a rate of only 40 to 90 mL/hr for the first 10 hours and requires 30 to 40 hours for completion.³⁴ However, patients evidencing hemorrhagic shock with a blood loss of at least 40% demonstrate much faster plasma refill rates, estimated as high as 1500 mL in the first 90 minutes after injury, with significant decreases in hematocrit within this period. Although the hematocrit is an easily acquired measure, it is often a conundrum when viewed in isolation, and serial determinations are more helpful.

White Blood Cell Count.: The white blood cell (WBC) count has little discriminatory value in cases of abdominal trauma, particularly its acute phase.³³ The WBC count may be normal or may show a modest leukocytosis (12,000 to 20,000/mm³ with or without left shift), which can occur in the setting of multisystem trauma as a result of stress-induced demargination in the absence of any intra-abdominal process, or as a result of tissue injury, acute hemorrhage, or peritoneal irritation.

Pancreatic Enzymes.: Neither serum amylase nor lipase is useful in the evaluation of acute abdominal trauma. Normal levels do not exclude a major pancreatic injury, and elevated values may be caused by any of an assortment of reasons in addition to an injured pancreas. The use of serum amylase isoenzymes has not appreciably improved accuracy. Nontraumatic causes of hyperamylasemia include several diseases and the use of alcohol, opioids, and various other drugs. Amylase or lipase may also be elevated with pancreatic ischemia produced by the systemic hypotension that often accompanies trauma. Clearly, these enzymes are neither highly specific nor sensitive for pancreatic injuries. Elevated or rising levels may indicate damage but in themselves are not conclusive.³⁵ In these cases, clinical correlation and further investigation are indicated.

Base Deficit.: Metabolic acidosis in the setting of trauma can suggest the presence of hemorrhagic shock. This can be witnessed chemically as a decreased serum bicarbonate level, increased base deficit, or elevated serum lactate level. Although normal values do not exclude abdominal injury, substantive abnormalities, such as a base deficit greater than or equal to 6, may be predictive. These findings should be considered in clinical context, because the resolution of the laboratory findings will lag behind the clinical improvement of the patient.

Liver Function Tests.: Elevated serum transaminases can result from hepatic trauma but do not distinguish minor contusions from severe injury.³⁶ Alternatively, these may be symptomatic of alcohol-induced liver damage. Elevated liver transaminase levels may be useful for screening pediatric patients for intentional trauma (see Chapter 38). They may also play a role in pediatric patients in combination with a FAST examination as a screening tool to decrease the use of CT scanning, although serial physical examination is still required.³⁷

Toxicology Analysis.: Screens for ethanol and drugs are often used in trauma centers. Their utility in the management of abdominal trauma, per se, has not been established, particularly in patients with normal mental status.³⁸ Positive study findings may prompt the emergency physician to interdict and the patient to decrease the recidivistic use of ethanol or drugs, and physician intervention during this “teaching moment” has been shown to be effective.

Advantages.: In most situations, CT scanning has supplanted DPL because of its higher predictive ability for operative lesions and because it is noninvasive. CT scanning can define the injured organ and the extent of the injury. It is most accurate for solid visceral lesions and accurately discerns the presence, source, and approximate quantity of intraperitoneal hemorrhage (Fig. 46-3). It can demonstrate active bleeding from the liver or spleen and can be used to determine whether therapeutic angiographic embolization is indicated.⁴⁰ CT scanning also evaluates the retroperitoneum (Fig. 46-4), an area not sampled by DPL, as well as the vertebral column, and can be readily extended above or below the abdomen to visualize the thorax or pelvis.⁴¹ CT scanning also provides definitive evaluation for most possible injuries to the urinary tract, including renal artery injury.⁴² It can also detect other vascular hemorrhage and obviate the need for angiography in some patients.⁴³ CT scanning is particularly helpful in guiding nonoperative management of solid organ damage.^44,45 This includes as-needed follow-up studies of convalescing patients with these injuries. It has also proven effective when incorporated in delayed fashion for patients with decreasing hematocrit, increasing base deficit, or subtle examination changes. By minimizing the incidence of nontherapeutic laparotomies for self-limited injury to the liver or spleen, it decreases morbidity and cost attendant to this operation.⁴⁶ Increasingly, trauma centers are using CT with intravenous contrast only, as it has been shown that little additional information is provided by the addition of oral contrast, which delays scanning and may pose an aspiration risk for the patient.^47,48

Disadvantages.: Disadvantages of CT scanning include relative insensitivity for injury of the pancreas, diaphragm, small bowel, and mesentery, although detection of these injuries is improving47,48 (Fig. 46-5). The last two are particularly worrisome because isolated coincidental hollow viscus injury in patients with blunt trauma, although uncommon, is not rare, and increased morbidity and death can ensue if diagnosis is missed or the condition goes undetected for a prolonged period. Findings on CT scans, including the suspected quantity of hemoperitoneum or the presence of isolated free fluid, are not able to forecast well the need for operative intervention.⁴⁹ Complications can result from intravenous contrast administration or uncommonly from contrast material administered orally. Moreover, oral contrast delivery to opacify bowel is infrequently useful and typically omitted.^47,50 Finally, patients must be temporarily removed from the resuscitation area for the study to be accomplished, which can put the patient at risk in the case of rapid clinical deterioration. However, CT scanning remains the cornerstone of diagnosis. In cases with equivocal CT scan results, such as more than physiologic fluid, or a worrisome history and physical examination findings, serial examinations or further diagnostic testing should be strongly considered, including DPL, particularly to evaluate for missed hollow viscus injury (Table 46-1).