Overview of Abdominal Trauma

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 table Grades of Hepatic Injury), spleen (see table Grades of Splenic Injury), and kidneys (see classification of renal injuries).

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

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, abdominal compartment syndrome, and delayed incisional hernia also can be complications of treatment.

Hematomas typically resolve spontaneously over several days to months, depending on the size and location. Splenic hematomas 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 hours 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 weeks after blunt trauma.

Intra-abdominal abscess 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 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 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 after orthopedic injury. In abdominal compartment syndrome, mesenteric and intestinal capillary leakage (eg, due to shock, prolonged abdominal surgical procedures, systemic ischemia-reperfusion injury, or 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 cycle. 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)

• Central nervous system (intracranial pressure increases, possibly due to rise in central venous pressure preventing adequate venous drainage from brain, 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.

Penetrating injuries by definition cause a break in the skin, but clinicians must be sure to inspect the back, buttocks, perineum, flank, 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.

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.

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 genitourinary tract injury. Although these findings are quite specific, they are not very sensitive.

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, diagnostic peritoneal lavage (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 and/or DPL 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.

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 patients with obesity and in patients with subcutaneous air (eg, due to pneumothorax).

Extended Focused Assessment Wi...

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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 diagnostic peritoneal lavage (DPL), a peritoneal dialysis catheter is placed through the abdominal wall near the umbilicus into the pelvic/peritoneal cavity. Aspiration of gross 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 red blood cells (RBCs)/microL (100 x 10⁹/L) 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 result.

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.

1. Como JJ, Bokhari F, Chiu WC, et al: Practice management guidelines for selective nonoperative management of penetrating abdominal trauma. J Trauma 68(3):721-733, 2010. doi: 10.1097/TA.0b013e3181cf7d07

Observation (beginning in an intensive care unit [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 a complete blood count (CBC) is done, typically every 4 to 6 hours. 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-hour period)

• A significant decrease in hematocrit (Hct; eg, by > 10 to 12 percentage points)

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 diagnostic peritoneal lavage (DPL), CT, or in some cases, exploratory laparotomy.

Patients who remain stable are typically transferred to a regular floor after 12 to 48 hours, 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 weeks.

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 injuries are at the highest risk for postinjury complications and should have the lowest threshold for repeat imaging.

Laparotomy is selected 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 initial 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 hemorrhage and enteric spillage are controlled (eg, by packing, ligation, shunting, oversewing, or stapling bowel) without definitive repair 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 hours—or sooner if they deteriorate clinically despite resuscitation. Because patients requiring damage control procedures are the most seriously injured, mortality is still significant and subsequent intra-abdominal complications are common.

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. However, with increasing availability of hybrid operating suites (operating room with angiographic intervention capabilities), some unstable patients may be able to undergo angiography and surgical management in rapid succession if needed.

1. Holcomb JB, Tilley BC, Baraniuk S, et al: Transfusion of plasma, platelets, and red blood cells in a 1:1:1 vs a 1:1:2 ratio and mortality in patients with severe trauma. JAMA 313(5):471-482, 2015. doi: 10.1001/jama.2015.12