79 Blunt Abdominal Trauma

Carlo L. Rosen, Eric L. Legome, Richard E. Wolfe

• Intraperitoneal bleeding is an immediately life-threatening injury after blunt trauma.

• Management of intraperitoneal bleeding takes priority over injuries to many other systems (Box 79.1).

• Physical examination is unreliable for predicting the presence or absence of injury except for certain high-risk findings such as the seat belt and Kehr signs.

• Bedside ultrasonography is an excellent initial screening tool that facilitates early triage of patients for either laparotomy or transfer to the radiology suite for computed tomography (CT).

• Helical CT provides excellent, accurate detail of intraperitoneal injuries. CT is highly sensitive for solid organ injuries but has lower sensitivity for detecting pancreatic, small bowel, and diaphragmatic injuries.

• Detailed CT images allow grading of organ injuries and nonoperative management of solid organ trauma in stable patients and the use of angiographic embolization in patients with liver, spleen, and renal injuries.

• Early detection of intraperitoneal injuries after blunt trauma and a team approach to management of these injuries significantly improve mortality rates.

Box 79.1 Management of Intraperitoneal Injuries

Intraperitoneal bleeding is an immediately life-threatening injury after blunt trauma, and management of intraperitoneal bleeding takes priority over injuries to other systems.

Physical examination is unreliable in predicting the presence or absence of injury except for certain high-risk findings such as the seat belt and Kehr signs.

Bedside ultrasonography is an excellent initial screening tool that facilitates early triage of patients to either laparotomy or the radiology suite for computed tomography (CT).

CT is highly sensitive for detecting solid organ injuries but has lower sensitivity for detecting pancreatic, small bowel, and diaphragmatic injuries.

Detailed CT allows grading of organ injuries and nonoperative management of solid organ trauma in stable patients and the use of angiographic embolization in patients with liver, spleen, and renal injuries.

Epidemiology

In the United States, trauma is a serious health problem, both as a cause of mortality and as a significant financial burden.¹ In recent years, management of blunt abdominal trauma has started to change because of the high success rates of more conservative, nonoperative treatment. Such management is a safer, successful, and more cost-effective way to care for these patients and consequently has led to an increasingly selective approach to performing explorative laparotomy.

Abdominal injuries occur in approximately 1% of all trauma patients.² Blunt trauma is far more common than penetrating trauma in the United States and is associated with greater mortality because of multiple related injuries and greater diagnostic and therapeutic challenges. The mechanism of blunt trauma may range from high-speed injuries to minor falls or direct blows to the abdomen. Motor vehicle collisions are responsible for approximately 75%, blows to the abdomen for approximately 15%, and falls for approximately 9% of injuries.³ Evaluation is further complicated by extraabdominal injuries, as well as by altered mental status from head trauma, alcohol intoxication, or recreational drugs.

Pathophysiology

Blunt trauma leads to injury when the elastic limit or breaking point of an organ is exceeded by the impact force applied. Impact force is defined by the amount of energy involved (e.g., the speed of a vehicle, the height of a fall), the location and surface of the blow to the body, and the duration of the impact. Understanding the mechanism of injury is imperative for assessing the initial risk and subsequent evaluation.

The risk for injury may vary slightly according to predisposing factors such as age and gender. Because men are more commonly engaged in dangerous activities, they are more frequently injured than women. A gravid uterus in a pregnant woman may offer some degree of protection to the intraperitoneal structures but adds the unique threat of placental abruption or uterine rupture.

A child’s abdomen is less well protected than an adult’s because of the thinner musculature, and it is far easier to injure abdominal organs such as the duodenum via compression against the posterior vertebrae. The elastic pediatric rib cage also provides less protection to the spleen and liver.

The risk for specific organ injury is linked to its structure and size. In particular, injuries to the spleen are far more common than injuries to other abdominal organs because of its poor elasticity. This is particularly true of abnormal spleens (e.g., patients with mononucleosis); such spleens are injured with far less force because of their larger size, which favors a greater mass effect, and because of their thinner capsule, which lacerates more easily. A spleen can be injured by a minor mechanism such as falling over a chair.

Blunt trauma can lead to injury to any abdominal structure. Direct, focused blows to the epigastrium may result in contusions and even perforation of the duodenum, as well as pancreatic injuries. Deceleration injuries may cause vascular sheering and subsequent thrombosis or tears of the renal artery (grade IV renal injury).

Anatomy

The abdominal compartment is bounded by the diaphragm, pelvis, and abdominal wall. The boundaries include the vertebral column and the muscles of the abdomen, the most important being the external oblique and rectus. The rib cage below the fourth intercostal space is considered part of the abdominal wall, and thus the abdominal compartment extends up into the chest.

The abdominal compartment is subdivided by the peritoneum into an anterior intraperitoneal cavity and the retroperitoneum. The lack of skeletal protection of the muscular anterior abdominal wall leads to a greater risk for injury to the intraperitoneal organs, notably the spleen, liver, and small bowel. Injured organs in the intraperitoneal cavity may bleed freely because of the substantial fluid capacity of this cavity, whereas brisk bleeding will be contained more by the limited space in the retroperitoneum.

Presenting Signs and Symptoms

Certain signs and symptoms suggest the presence of intraperitoneal injury. Blood pressure and heart rate are the most important vital signs when assessing for significant intraabdominal injury. Isolated prehospital hypotension has been shown to be a predictor of mortality and of chest or abdominal injury requiring operative intervention. Prehospital abnormal vital signs should not be discounted even if the patient arrives with “stable” vital signs. Normal vital signs do not rule out intraperitoneal injury.

Patients in shock usually demonstrate tachycardia. However, up to 44% of trauma patients in shock may have relative bradycardia, defined as a heart rate of less than 90 beats per minute and a systolic blood pressure lower than 90 mm Hg. Relative bradycardia has been identified as an independent risk factor for mortality.⁴

Significant complaints and findings include abdominal pain or tenderness, ecchymoses and abrasions on the abdominal wall, and hematemesis. Increasing abdominal distention may be a marker of ongoing intraperitoneal bleeding. Peritonitis, even in the absence of hypotension, is a strong predictor of intraabdominal injury, although it does not necessarily predict the need for laparotomy in a stable patient.

Physical examination is limited in its ability to identify the presence or absence of intraabdominal injury. Therefore, further diagnostic testing should be performed, despite minimal clinical findings, if the abdomen sustained significant direct trauma such as a baseball bat or handlebar injury or if the patient is difficult to evaluate because of concomitant injuries or altered mental status for any reason. Other significant mechanisms, such as a rollover motor vehicle collision, a motor vehicle collision with ejection or significant intrusion, or a substantial fall, should be evaluated in light of the patient’s clinical picture. A motor vehicle collision with steering wheel deformity is associated with serious abdominal injury in front seat passengers but not in drivers; direct impact from a bicycle handlebar suggests an increased likelihood of abdominal injury requiring laparotomy. Intraperitoneal injury can also result from minor mechanisms, such as a fall from the standing position onto the abdomen.

Several insensitive clinical signs suggest specific injuries in a blunt trauma patient. The Kehr sign, which is left shoulder pain, suggests splenic rupture. The Cullen sign is ecchymosis around the umbilicus, and the Turner sign is ecchymosis in the flank area. These signs suggest retroperitoneal hemorrhage but are very rarely found in acute trauma patients. They occur only hours after injury and thus are of little use in the initial assessment of patients who have sustained blunt abdominal trauma.

The presence of the seat belt sign (erythema, ecchymosis, or abrasions in the pattern of a seat belt) is associated with intraperitoneal injuries—specifically, pancreatic, hollow viscus, and mesenteric injuries. Multiple studies have shown a significantly higher incidence of intraabdominal operative pathology in patients with the seat belt sign than in those lacking this sign after motor vehicle trauma. The seat belt sign usually results from incorrect use or improper placement of a seat belt restraint. It should be used as a predictor of intraperitoneal injury and therefore as an indication to perform diagnostic imaging in patients with blunt abdominal trauma. Negative findings on computed tomography (CT) in a patient with abdominal tenderness and the seat belt sign should be followed by observation, diagnostic peritoneal lavage (DPL), or laparotomy, depending on the findings and clinical suspicion. Although evisceration and clear-cut peritonitis are diagnostic of intraabdominal pathology, neither is a common finding.

Abdominal tenderness is often absent in patients with intraperitoneal injury. Drugs, alcohol, hypotension, and the presence of head injury reduce the patient’s ability to sense pain or tenderness. Additionally, other significant injuries such as fractures or large lacerations may distract the patient from feeling the pain associated with abdominal injury. In a large prospective study, 19% of patients with positive findings on CT for intraabdominal injury did not have abdominal tenderness.³ Other studies have reported abdominal tenderness in only 42% to 75% of patients with small bowel or mesenteric injury.^5,⁶ The sensitivity, specificity, and negative and positive predictive values of abdominal pain or tenderness in predicting intraabdominal injury are reported to be 82%, 45%, 93%, and 21%, respectively.⁷ Furthermore, patients with chest wall injuries and pneumothorax are at risk for injury and may not exhibit abdominal pain or tenderness. Thus, it is important to avoid relying solely on the physical examination, especially in a multitrauma patient or one with altered mental status, when deciding whether to perform diagnostic testing on a patient after blunt abdominal trauma.

Evaluation

Physical examination of the abdomen following trauma consists of observation and palpation. The abdomen should be observed for signs of disruption, evisceration, ecchymoses, abrasions, and distention. Although it is important to perform a rectal examination to assess rectal tone and the prostate for possible urethral injury, a positive stool guaiac test is not predictive of injury. If gross blood is present on rectal examination, large bowel or rectal injury should be suspected.

Red Flags

Prehospital hypotension indicates the need for diagnostic imaging of the abdomen.

Abdominal ecchymosis is predictive of intraperitoneal injury.

The presence of a Chance fracture is predictive of intraperitoneal injury.

Left shoulder pain suggests splenic injury.

Low rib fractures are associated with liver and spleen injuries.

The initial physical examination includes assessment of the pelvis for stability and the urethral meatus for blood as an indicator of associated urethral injury. These aspects of the examination will help the emergency physician (EP) plan the subsequent evaluation. Patients with pelvic instability may need stabilization of a pelvic fracture and embolization, whereas those with a urethral injury may need retrograde urethrography and suprapubic placement of a Foley catheter.

Differential Diagnosis

The specific injuries to be concerned with after blunt abdominal trauma can be broken down into several categories: solid organ (liver and spleen), hollow viscus, mesenteric, vascular (inferior vena cava and aorta), diaphragmatic, and retroperitoneal (renal, bladder, pelvic fractures, and vascular). Other less common injuries are gallbladder, pancreas, and rectus sheath hematomas.

Chance Fractures

A single lap belt restraint can result in Chance fractures of the lumbar spine. In a recent report, 33% of patients with Chance fractures had associated intraabdominal injury, and of these patients, 22% had hollow viscus injuries.⁸ In other studies, up to 89% of patients with Chance fractures had small bowel injuries.^5,⁹ Some centers consider the presence of Chance fractures and the seat belt sign to be an indication for exploratory laparotomy.

Upper Abdominal Injuries

Low rib injuries may be associated with spleen or liver trauma, as well as kidney injuries. The incidence of splenic injury in patients with “isolated” low rib pain or tenderness (no abdominal tenderness) was 3% in a recent report. Although the only prospective study on the subject is not definitive, it suggests that patients with pleuritic pain and isolated low left rib pain or tenderness, regardless of whether abdominal tenderness is present, should undergo imaging.¹⁰ In addition, patients with abdominal tenderness following low chest trauma should undergo diagnostic imaging (e.g., CT).

Lower Abdominal Injuries

Blunt abdominal trauma may result in retroperitoneal injury to the kidneys or ureters. Intraperitoneal or extraperitoneal bladder rupture may also occur. Major pelvic fractures are associated with abdominal injuries in 30% of patients.¹¹ Injury to the abdominal aorta is rare after blunt abdominal trauma. Other less serious injuries are abdominal wall hematomas, which do not usually require operative intervention but can result in significant blood loss.

Injuries with Delayed Presentation

Several injuries are notoriously seen in delayed fashion or have subtle clinical findings. Pancreatic injuries may be manifested as abdominal pain and tenderness several hours after the trauma. Duodenal hematomas typically become evident 5 to 7 days after the trauma as vague abdominal pain and vomiting. This is in contrast to patients with duodenal perforations, who usually have acute pain and tenderness immediately after the trauma.

Traumatic diaphragmatic hernia can also occur in delayed fashion. These injuries are frequently missed because the sensitivity of CT for diaphragmatic injuries is low and the majority of patients have associated injuries.¹² Most of these injuries result from a vehicular collision. Because the right hemidiaphragm is protected by the liver, the left hemidiaphragm is more commonly involved.

Diaphragmatic injuries occur in three phases. In the acute phase, immediately after injury, patients may have decreased or absent breath signs on one side of the chest or bowel sounds in the chest. If the injury is not detected, patients may go through a latent phase consisting of intermittent visceral herniation into the chest through the diaphragmatic rupture. These patients may have vague postprandial abdominal pain (which improves with standing because the herniated bowel is reduced), nausea, vomiting, and belching. During this phase the injury can go undetected for months to years. With time, patients will eventually enter the obstructive phase, which is associated with herniation and incarceration of bowel, intestinal obstruction, and ischemia. These patients exhibit abdominal pain, distention, and vomiting.

In the acute setting, patients with a diaphragmatic injury can also have tension viscerothorax–herniation of bowel into the chest, which results in increased intrathoracic pressure and mediastinal shift with compression of the superior vena cava. These patients have hypotension and decreased breath sounds on the affected side of the chest.

Solid Organ Injuries

The most common type of injury is solid organ injury. More than 90% of the injuries sustained in blunt trauma are isolated to the liver and spleen. Patients with hypotension as a result of blunt trauma usually have free rupture of a solid organ. Delayed onset of symptoms or pain without hypotension should raise concern about encapsulated hepatic or splenic trauma or hollow viscus injury. Although most intraperitoneal injuries today are managed nonoperatively, delayed diagnosis in some cases can lead to severe morbidity or mortality. Free intraperitoneal bleeding is the most urgent diagnosis in patients with blunt abdominal trauma. This immediately life-threatening condition may require interventions, including transfusion, exploratory laparotomy, and angiography with embolization.

Priority Actions

1. Follow the advanced trauma life support protocols for initial resuscitation.

2. Determine the stability of the patient.

3. Perform chest and pelvic radiography on all unstable trauma patients.

4. Perform ultrasound examination on all major trauma patients.

5. Arrange transfer immediately for all patients with multisystem trauma or with the potential for intraperitoneal injury if a trauma surgeon is not available.

6. Triage the patient to either computed tomography scanning, laparotomy, the angiography suite (pelvic fractures or for embolization of abdominal injuries), intensive care unit, admission for observation, or discharge.

The Unstable Patient

Initial Management

The initial therapeutic intervention in patients with presumed intraperitoneal injury is to address the ABCs of trauma (airway, breathing, and circulation). Initially, all patients should receive high-flow oxygen. Intubation should be performed on unstable or severely injured multitrauma patients or those with the potential for rapid decline. After breathing is attended to, circulatory status is addressed. Antecubital venous or central line access should be obtained.

Immediate Operative Intervention

There are several indications to proceed immediately to the operating room without further diagnostic testing, including evisceration, gross blood per rectum, blood per nasogastric tube or hematemesis, evidence of diaphragmatic injury, and hemodynamic instability with evidence of intraperitoneal injury (e.g., positive ultrasound findings).

Focused Abdominal Sonography for Trauma

Bedside ultrasonography has many advantages as an initial triage tool in an unstable trauma patient. It is readily accessible at most level I trauma centers and, in the hands of trained EPs, is accurate in detecting hemoperitoneum.¹³ Focused abdominal sonography for trauma (FAST) can be performed in less than 2 minutes and can triage patients to the operating room or further diagnostic testing, depending on the patient’s stability. In trauma patients, the incidence of an indeterminate sonographic result is low (less than 7%),¹⁴ and the reported sensitivity and negative predictive value in unstable patients approach 100%.^15,¹⁶ The presence of hemoperitoneum in an unstable patient is an indication for operative intervention. The only caveat is that in patients with major pelvic trauma who may have bladder rupture with uroperitoneum, diagnostic peritoneal aspiration may be indicated to distinguish blood from urine. If the sonographic findings are negative, other sources of bleeding should be addressed, such as pelvic fractures and retroperitoneal bleeding.