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Overview of Abdominal Trauma

by Darren Malinoski, MD

The abdomen can be injured in many types of trauma; injury may be confined to the abdomen or be accompanied by severe, multisystem trauma. The nature and severity of abdominal injuries vary widely depending on the mechanism and forces involved, thus generalizations about mortality and need for operative repair tend to be misleading.

Injuries are often categorized by type of structure that is damaged:

  • Abdominal wall

  • Solid organ (liver, spleen, pancreas, kidneys)

  • Hollow viscus (stomach, small intestine, colon, ureters, bladder)

  • Vasculature

Some specific injuries due to abdominal trauma are discussed elsewhere, including those to the liver (see Hepatic Injury), spleen (see Splenic Injury), and GU tract (see Genitourinary Tract Trauma).

Etiology

Abdominal trauma is typically also categorized by mechanism of injury:

  • Blunt

  • Penetrating

Blunt trauma may involve a direct blow (eg, kick), impact with an object (eg, fall on bicycle handlebars), or sudden deceleration (eg, fall from a height, vehicle crash). The spleen is the organ damaged most commonly, followed by the liver and a hollow viscus (typically the small intestine).

Penetrating injuries may or may not penetrate peritoneum and if they do, may not cause organ injury. Stab wounds are less likely than gunshot wounds to damage intra-abdominal structures; in both, any structure can be affected. Penetrating wounds to the lower chest may cross the diaphragm and damage abdominal structures.

Classification

Injury scales have been devised that classify organ injury severity from grade 1 (minimal) to grades 5 or 6 (massive); mortality and need for operative repair increase as grade increases. Scales exist for the liver (see Grades of Hepatic Injury), spleen (see Grades of Splenic Injury ), and kidneys ( Grades of Renal Injury).


Associated injuries

Blunt or penetrating injury that affects intra-abdominal structures may also damage the spine and/or pelvis. Patients who experience significant deceleration often have injuries to other parts of the body, including the thoracic aorta.


Pathophysiology

Blunt or penetrating trauma may lacerate or rupture intra-abdominal structures. Blunt injury may alternatively cause only a hematoma in a solid organ or the wall of a hollow viscus.

Lacerations hemorrhage immediately. Hemorrhage due to low-grade solid organ injury, minor vascular laceration, or hollow viscus laceration is often low-volume, with minimal physiologic consequences. More serious injuries may cause massive hemorrhage with shock, acidosis, and coagulopathy (see Shock); intervention is required. Hemorrhage is internal (except for relatively small amounts of external hemorrhage due to body wall lacerations resulting from penetrating trauma). Internal hemorrhage may be intraperitoneal or retroperitoneal.

Laceration or rupture of a hollow viscus allows gastric, intestinal, or bladder contents to enter the peritoneal cavity, causing peritonitis.

Complications

Delayed consequences of abdominal injury include

  • Hematoma rupture

  • Intra-abdominal abscess

  • Bowel obstruction or ileus

  • Biliary leakage and/or biloma

  • Abdominal compartment syndrome

Abscess, bowel obstruction, and abdominal compartment syndrome also can be complications of treatment.

Hematomas typically resolve spontaneously over several days to months, depending on the size and location. Splenic and, less often, hepatic hematomas may rupture, typically in the first few days after injury (although sometimes up to months later), sometimes causing significant delayed hemorrhage. Intestinal wall hematomas sometimes perforate, typically within 48 to 72 h after injury, releasing intestinal contents and causing peritonitis, but without causing significant hemorrhage. Intestinal wall hematomas rarely can cause intestinal stricture, typically months to years later, although there are case reports of bowel obstruction as early as 2 wk after blunt trauma.

Intra-abdominal abscess (see Intra-Abdominal Abscesses) typically is the result of undetected hollow viscus perforation but may be a complication of laparotomy. Rate of abscess formation ranges from 0% after nontherapeutic laparotomies to about 10% after therapeutic laparotomies, although the rate may be as high as 50% after surgery to repair severe liver lacerations.

Bowel obstruction (see Intestinal Obstruction) rarely develops in weeks to years after injury due to intestinal wall hematoma or adhesions caused by intestinal serosal or mesenteric tears. More commonly bowel obstruction is a complication of exploratory laparotomy. Even nontherapeutic laparotomies occasionally cause adhesions, which develop in 0 to 2% of such cases.

Biliary leakage and/or biloma (see Complications) is a rare complication of liver injury and, even less commonly, of bile duct injury. Bile can be excreted from the raw surface of a liver injury or from an injured bile duct. It may be disseminated throughout the peritoneal cavity or become walled off into a distinct fluid collection, or biloma. Biliary leakage can result in pain, a systemic inflammatory response, and/or hyperbilirubinemia.

Abdominal compartment syndrome is analogous to extremity compartment syndrome (see Compartment Syndrome) after orthopedic injury. In abdominal compartment syndrome, mesenteric and intestinal capillary leakage (eg, due to shock, prolonged abdominal surgical procedures, systemic ischemia-reperfusion injury, and the systemic inflammatory response syndrome [SIRS]) causes tissue edema within the abdomen. Although there is more room for expansion in the peritoneal cavity than in an extremity, unchecked edema, and occasionally ascites, ultimately elevates intra-abdominal pressure (defined as > 20 mm Hg), causing pain and organ ischemia and dysfunction. Intestinal ischemia further worsens vascular leakage, causing a vicious circle. Other affected organs include the

  • Kidneys (causing renal insufficiency)

  • Lungs (elevated abdominal pressure can interfere with respiration, causing hypoxemia and hypercarbia)

  • Cardiovascular system (elevated abdominal pressure decreases venous return from the lower extremities, causing hypotension)

  • CNS (intracranial pressure increases, possibly decreasing cerebral perfusion, which can worsen intracranial injuries)

Abdominal compartment syndrome typically occurs in conditions in which there is both vascular leak and high-volume fluid resuscitation (usually > 10 L). Thus, it often develops after laparotomy for severe abdominal injury accompanied by shock but may occur in conditions not primarily affecting the abdomen, such as severe burns, sepsis, and pancreatitis. Once multiorgan dysfunction develops, the only way to prevent mortality is to decompress the abdominal contents, typically with a laparotomy. Large-volume paracentesis may be effective when there is significant ascites.


Symptoms and Signs

Abdominal pain typically is present; however, pain is often mild and thus easily obscured by other, more painful injuries (eg, fractures) and by altered sensorium (eg, due to head injury, substance abuse, shock). Pain from splenic injury sometimes radiates to the left shoulder. Pain from a small intestinal perforation typically is minimal initially but steadily worsens over the first few hours. Patients with renal injury may notice hematuria.

On examination, vital signs may show evidence of hypovolemia (tachycardia) or shock (eg, dusky color, diaphoresis, altered sensorium, hypotension).

Inspection

Penetrating injuries by definition cause a break in the skin, but clinicians must be sure to inspect the back, buttocks, and lower chest in addition to the abdomen, particularly when firearms or explosive devices are involved. Cutaneous lesions are often small, with minimal bleeding, although occasionally wounds are large, sometimes accompanied by evisceration.

Pearls & Pitfalls

  • Not all penetrating abdominal injuries originate from wounds on the abdominal wall; be suspicious of entrance wounds on the back, buttocks, perineum, and lower chest.

Blunt trauma may cause ecchymosis (eg, the transverse, linear ecchymosis termed seat belt sign), but this finding has poor sensitivity and specificity. Abdominal distention after trauma typically indicates severe hemorrhage (2 to 3 L), but distention may not be apparent even in patients who have lost several units of blood.


Palpation

Abdominal tenderness is often present. This sign is very unreliable because abdominal wall contusions can be tender and many patients with intra-abdominal injury have equivocal examinations if they are distracted by other injuries or have altered sensorium or if their injuries are mainly retroperitoneal. Although not very sensitive, when detected, peritoneal signs (eg, guarding, rebound) strongly suggest the presence of intraperitoneal blood and/or intestinal contents.

Rectal examination may show gross blood due to a penetrating colonic lesion, and there may be blood at the urethral meatus or perineal hematoma due to GU tract injury. Although these findings are quite specific, they are not very sensitive.


Diagnosis

  • Clinical evaluation

  • Often CT or ultrasonography

As in all patients experiencing significant trauma, clinicians do a thorough, organized trauma evaluation simultaneous with resuscitation (see Approach to the Trauma Patient). Because many intra-abdominal injuries heal without specific treatment, the clinician's primary goal is to identify injuries requiring intervention.

Following clinical evaluation, a few patients clearly require exploratory laparotomy rather than testing, including those with

  • Peritonitis

  • Hemodynamic instability due to penetrating abdominal trauma

  • Gunshot wounds (most)

  • Evisceration

Conversely, a few patients are at very low risk and may be discharged or observed briefly without any testing other than visual inspection of the urine for gross blood. These patients typically have isolated blunt abdominal trauma and a minor mechanism of injury, normal sensorium, and no tenderness or peritoneal signs; they should be instructed to return immediately if pain worsens.

However, most patients do not have such clear-cut positive or negative manifestations and thus require testing to evaluate for intra-abdominal injury. Testing options include

  • Imaging studies (ultrasonography, CT)

  • Procedures (wound exploration, diagnostic peritoneal lavage [DPL])

In addition, patients usually should have a chest x-ray to look for free air under the diaphragm (indicating perforation of a hollow viscus) and an elevated hemidiaphragm (suggesting diaphragmatic rupture). Pelvis x-ray is done in patients with pelvic tenderness or significant deceleration and an unreliable clinical examination.

Laboratory testing is secondary. Urinalysis to detect hematuria (gross or microscopic) is helpful, and for patients with apparently serious injuries, CBC is valuable to establish baseline Hct. Pancreatic and liver enzyme levels are not sufficiently sensitive or specific for significant organ injury to be recommended. The blood bank should do a type and screen (see Compatible RBC types.) in case blood transfusions are necessary; type and cross-match is done if transfusion is very likely. Serum lactate level or base deficit calculation (from arterial blood gas testing) may help identify occult shock.

The method chosen to detect intra-abdominal injury varies by mechanism of injury and the clinical examination.

Penetrating trauma

Blindly probing wounds with a blunt instrument (eg, cotton swab, fingertip) should not be done. If the peritoneum has been violated, probing may introduce infection or cause further damage.

Stab wounds (including impalements) to the anterior abdomen (between the 2 anterior axillary lines) in hemodynamically stable patients without peritoneal signs can be explored locally. Typically, local anesthesia is given and the wound is opened enough to allow complete visualization of the entire tract. If the anterior fascia is penetrated, patients are admitted for serial clinical examinations; exploratory laparotomy is done if peritoneal signs or hemodynamic instability develop. If the fascia is not violated, the wound is cleansed and repaired and the patient discharged. Alternatively, some centers do CT, or less commonly, DPL, to evaluate patients with fascial penetration. CT is recommended for stab wounds to the flank (between the anterior and posterior axillary lines) or back (between the 2 posterior axillary lines) because injuries to the retroperitoneal structures underlying these areas can be missed when serial abdominal examinations are done.

For gunshot wounds, most clinicians do exploratory laparotomy unless the wound is clearly grazing or tangential and peritonitis and hypotension are absent. However, some centers that use nonoperative management of select patients with only solid organ (typically liver) injury do CT of stable patients with gunshot wounds. Local wound exploration is typically not done for gunshot wounds.

Blunt trauma: Most patients with multiple trauma and distracting injuries and/or altered sensorium should have testing of the abdomen as should patients with findings on examination. Typically, clinicians use ultrasonography or CT, or sometimes both.

Ultrasonography (sometimes termed focused assessment with sonography in trauma [FAST]) can be done during the initial assessment without moving the patient to the radiology suite. The FAST images the pericardium, right and left upper quadrants, and pelvis; its primary aim is to find abnormal pericardial fluid or intraperitoneal free fluid. An extended FAST (E-FAST) adds images of the chest aimed at detecting pneumothorax. Ultrasonography gives no radiation exposure and is sensitive for detecting larger amounts of abdominal fluid but does not identify specific solid organ injuries well, is poor at detecting viscus perforation, and is limited in obese patients and in patients with subcutaneous air (eg, due to pneumothorax).

CT is typically done with IV but not an oral contrast agent; this test is very sensitive for free fluid and solid organ injury but less so for small viscus perforations (albeit better than ultrasonography), and it can simultaneously detect injury to the spine or pelvis. However, CT exposes patients to radiation, which is a particular concern in children and in patients who may require repeat studies (eg, stable patients with small amounts of free fluid), and requires patient transport away from the resuscitation area.

Choice between ultrasonography and CT is based on patient status. If the patient needs CT to assess another body region (eg, cervical spine, pelvis), CT is probably the reasonable choice to evaluate the abdomen. Some clinicians do a FAST scan during the resuscitation phase and proceed to laparotomy if a large amount of free fluid is seen (in hypotensive patients). If FAST results are negative or weakly positive, clinicians do CT if there is still concern about the abdomen after the patient is stabilized. Reasons for such concern include increasing abdominal pain or anticipated inability to monitor the patient clinically (eg, patients who require heavy sedation or who will be undergoing lengthy surgical procedures).

In DPL, a peritoneal dialysis catheter is placed through the abdominal wall near the umbilicus into the pelvic/peritoneal cavity. Aspiration of blood is considered positive for abdominal injury. If no blood is aspirated, 1 L of crystalloid is run in and allowed to drain back out. Finding > 100,000 RBCs/mL of effluent is very sensitive for abdominal injury. However, DPL has largely been replaced by the FAST examination and CT. DPL has low specificity, identifying many lesions that do not require operative repair and thus resulting in a high negative laparotomy rate. DPL also misses retroperitoneal injuries. DPL may be useful in limited clinical situations such as when there is free pelvic fluid in the absence of a solid organ injury or a hypotensive patient with an unclear FAST examination results.


Complications

Patients with sudden worsening of abdominal pain in the days following injury should be suspected of having a ruptured solid organ hematoma or a delayed hollow viscus perforation, particularly if they have tachycardia and/or hypotension. Steadily worsening pain within the first day suggests hollow viscus perforation or, if after several days, abscess formation, particularly if accompanied by fever and leukocytosis. In both cases, imaging with ultrasonography or CT is usually done in stable patients, followed by operative repair.

Following severe abdominal trauma, abdominal compartment syndrome should be suspected in patients with decreased urine output, ventilatory insufficiency, and/or hypotension, particularly if the abdomen is tense or distended (however, physical findings are not very sensitive). Because such manifestations can also be signs of decompensation due to the underlying injuries, a high degree of suspicion is required in at-risk patients. Diagnosis requires measuring intra-abdominal pressure, typically with a pressure transducer connected to the bladder catheter; values > 20 mm Hg are diagnostic of intra-abdominal hypertension and are concerning. When patients with such a reading also have signs of organ dysfunction (eg, hypotension, hypoxia/hypercarbia, decreased urine output, increased intracranial pressure), surgical decompression is done. Typically the abdomen is left open with the wound covered by a vacuum pack dressing or other temporary device.


Treatment

  • Sometimes laparotomy for hemorrhage control, organ repair, or both

  • Rarely arterial embolization

Patients are given fluid resuscitation as needed (see Intravenous Fluid Resuscitation). Some hemodynamically unstable patients are taken for immediate exploratory laparotomy as described above. For the majority of patients who do not require immediate surgery but who have intra-abdominal injuries identified during imaging, management options include observation, angiographic embolization, and less frequently operative intervention. Prophylactic antibiotics are not indicated when patients are managed without surgery. However, antibiotics are often given before surgical exploration when patients develop an indication for surgery.

Observation

Observation (beginning in an ICU) is often appropriate for hemodynamically stable patients with solid organ injury, many of which heal spontaneously. Patients with free fluid seen during CT but no specific organ injury identified may also be observed provided they have no peritoneal signs. However, free fluid without evidence of solid organ injury is also the most frequent radiographic finding in hollow viscus injury, although this finding has low specificity. Because observation is not appropriate for hollow viscus perforation (patients typically develop sepsis due to peritonitis), clinicians should have a lower threshold for operative exploration when patients with isolated free fluid worsen or fail to improve during a period of observation.

During observation, patients are examined several times per day (preferably by the same examiner), and CBC is done, typically every 4 to 6 h. Assessment seeks to identify ongoing hemorrhage and peritonitis.

Ongoing hemorrhage is suggested by

  • Worsening hemodynamic status

  • Significant ongoing transfusion needs (eg, more than 2 to 4 units over a 12-h period)

  • A significant decrease in Hct (eg, by > 10 to 12%)

The significance of transfusion requirements and change in Hct depend somewhat on the organ injured and other associated injuries (ie, that may also have caused blood loss) as well as the patient's physiologic reserves. However, patients suspected of significant ongoing hemorrhage should be considered for angiography with embolization or immediate laparotomy.

Peritonitis requires further investigation by DPL, CT, or in some cases, exploratory laparotomy.

Patients who remain stable are typically transferred to a regular floor after 12 to 48 h, depending on the severity of their abdominal and other injuries. Their activity and diet are advanced as tolerated. Typically, patients may be discharged home after 2 to 3 days. They are instructed to restrict activity for a minimum of 6 to 8 wk.

It is not clear which asymptomatic patients require an imaging study before resuming full activity, especially when heavy lifting, contact sports, or torso trauma are likely to occur. Patients with high grade (ie, grade 4 and 5) injuries are at the highest risk for postinjury complications and should have the lowest threshold for repeat imaging.


Laparotomy

Laparotomy is elected either because of the initial nature of the injury and clinical status (eg, hemodynamic instability) or because of subsequent clinical decompensation. Most patients can have a single procedure during which hemorrhage is controlled and injuries repaired.

However, patients with extensive intra-abdominal injuries who undergo a prolonged surgical procedure tend to fare poorly, particularly when they have other serious injuries, have been in shock for a prolonged period, or both. The more extensive and lengthy the initial surgical procedure, the more likely such patients are to develop the highly lethal combination of acidosis, coagulopathy, and hypothermia with subsequent multiple organ dysfunction. In such cases, mortality can be lessened if the surgeon initially does a much briefer procedure (termed damage control surgery) in which the worst hemorrhage is controlled but other injuries are simply packed and the abdomen temporarily closed. Temporary closure can be achieved using a closed suction vacuum system constructed from towels, drains, and large bio-occlusive dressings or through use of a commercially available negative-pressure abdominal dressing. Patients are then stabilized in the ICU and taken for packing removal and definitive repair once normal physiology has been restored (particularly correction of pH and temperature), typically within 24 h. Because patients requiring damage control procedures are the most seriously injured, mortality is still significant and subsequent intra-abdominal complications are common.


Angiographic embolization

Ongoing bleeding can sometimes be stopped without surgery by embolizing the bleeding vessel using a percutaneous angiographic procedure (angiographic embolization). Hemostasis is obtained by injecting a thrombogenic substance (eg, powdered gelatin) or metallic coils into the bleeding vessel. Although there is not complete consensus, generally accepted indications for angiographic embolization include

  • Pseudoaneurysm

  • Arteriovenous fistula

  • Solid organ injury (particularly of the liver) or pelvic fracture with bleeding severe enough to require postresuscitation transfusion

Angiographic embolization is not recommended for unstable patients because the radiology suite is a suboptimal area for providing critical care. Additionally, prolonged attempts at embolization should be discouraged in patients whose bleeding requires continued transfusion; operative management is more appropriate.


Key Points

  • Complications of abdominal injuries can be acute (eg, bleeding) or delayed (eg, abscess, obstruction or ileus, delayed hematoma rupture).

  • The abdominal examination does not reliably indicate the severity of abdominal injury.

  • If patients have evisceration, shock due to penetrating abdominal trauma, or peritonitis, do exploratory laparotomy without delay for diagnostic testing.

  • Unless there is clear evidence that laparotomy is indicated or the mechanism of injury is minor, imaging (typically ultrasonography or CT) is typically required after blunt or penetrating trauma.

  • If pain gradually increases or clinical signs suggest deterioration, suspect a delayed complication.

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