Liver Injury

Introduction

Liver injuries are one of the most common injuries to occur after trauma. The liver’s large size and exposed position under the right costal margin make it one of the most regularly injured organs in blunt and penetrating abdominal trauma.^[1] The majority of liver injuries can be managed non-operatively, only the most severe injuries risk exsanguinating hemorrhage necessitating massive resuscitation protocols and emergent laparotomy.^[1,2]

The American Association for the Surgery of Trauma uses radiologic findings to classify liver injuries according to the Organ Injury Scale.^[3] Interventional radiologic procedures have evolved into important tools for the treatment of hepatic trauma. Injuries to the liver can vary in severity; this article provides an overview of the approach and management of hepatic trauma.

Clinical Presentation

Upon arrival in the trauma bay, first responders may provide information regarding the mechanism of injury or further history that may elucidate whether liver trauma is present. Truncal trauma, especially to the anterior or lateral thoracoabdominal region, right upper quadrant, or right flank, should raise suspicion for this. The patient may be hemodynamically stable or unstable depending on the severity of the injury.

Abdominal tenderness or peritoneal signs may or may not be present. Abdominal distension in the setting of trauma might suggest hemoperitoneum originating from the liver. In high-impact motor vehicle accidents, a “seatbelt sign” may be present and has been associated with intraabdominal solid organ injury.^[4] Importantly, hemodynamic stability and/or absence of abdominal pain does not preclude liver injury in blunt or penetrating trauma.

Evaluation

A standardized trauma evaluation guided by the fundamentals of Advanced Trauma Life Support (ATLS) should be performed. This begins with the primary survey and identification of hemodynamic instability. Resuscitation efforts should begin during this time. Crystalloids can be used during initial resuscitation while awaiting blood products, but excessive amounts of crystalloid solution should be avoided. If whole blood or blood products are immediately available they are the first choice for resuscitation fluid in trauma.

Administration of blood products should be performed in a 1:1:1 ratio with packed red blood cells, fresh frozen plasma, and platelets.^[2]

Laboratory evaluation

A routine set of laboratory tests should be obtained when possible. These include complete blood count (CBC), comprehensive metabolic panel (CMP) (encompassing liver function tests), coagulation markers, and lactate. Liver function tests may or may not be abnormal on initial labs depending on the timing of the injury. These can take hours to days to become abnormal. Additionally, a type and crossmatch are critical in patients with severe hepatic injury requiring massive transfusion.

Radiologic evaluation

Focused abdominal sonography for trauma (FAST) exam is a rapid radiologic tool that can be used in the trauma bay to identify hemoperitoneum. Signs of hepatic injury on FAST include visualization of subcapsular fluid, perihepatic fluid, or fluid in the hepatorenal space (Morrison’s Pouch).^[5]

Chest and abdominal x-rays are also necessary to isolate potential sources of bleeding but will not rule out hepatic bleeding. Computed tomography (CT) is a widely used imaging modality in the management of trauma patients and has proven vital in the diagnosis and management of liver injury. In patients who are hemodynamically stable, CT imaging is strongly recommended. Contrast-enhanced CT can detect parenchymal, vascular, and biliary injuries. Multiphasic imaging with CT further characterizes the type of vascular injury and presence of active bleeding.^[6] It is important to remember that an unstable patient does not belong in the CT scanner.

Grade of Injury

The American Association for the Surgery of Trauma (AAST) developed a widely accepted injury grading scale to classify the severity of liver injuries. This uses radiologic, operative, and pathologic criteria to assign grades. Higher grades are more severe and associated with a higher chance of failure of nonoperative management requiring procedural intervention. Grade of injury does not necessarily indicate whether operative vs nonoperative management should be pursued, but rather provides a standardized, systematic method to describe injuries. However, higher grades of injury are associated with higher morbidity and mortality.^[7]

Anatomy ^[8]

A brief review of anatomy is important for any surgeon managing liver trauma. The liver is the largest organ in the body and inhabits the upper right quadrant of the abdomen, just beneath the diaphragm. The falciform ligament is a two-layered fold of peritoneum that connects the liver to the anterior abdominal wall and visually divides the liver into two sides. The two layers of the falciform ligament diverge on the superior surface of the liver into the coronary and left triangular ligament. This ligament is important because it is continuous with the lesser omentum. The liver is anatomically divided into right and left hepatic lobes by Cantlie’s line running from the gallbladder to the IVC.

On the visceral surface of the liver can be found the gallbladder, fissure for the round ligament, and the porta hepatis. This is a “cleft” through which pass the branches of the proper hepatic artery, portal vein, and the hepatic ducts. Blood supply to the liver is through the proper hepatic artery and portal vein which enter via the porta hepatis. Blood is drained via the hepatic veins in the organ directly into the suprahepatic IVC. The liver can be functionally divided into eight segments, each with its own portal triad (portal vein, hepatic artery, and bile duct), which is why the organ is so vascular and prone to massive hemorrhage when traumatized.^[9]

Management

Blunt vs. Penetrating Liver Injury

The mechanism of injury is important when determining the management of liver injuries. Blunt hepatic trauma as seen in motor vehicle collisions or falls results in deceleration injuries. This causes the liver to tear at sites that are fixed to the abdominal wall and diaphragm. The result is vascular injury to the hepatic veins which have a less fibrous structure than arterial structures. In severe injuries, the portal system can be disrupted causing massive hemorrhage.

In general, the right hepatic lobe is more likely to be injured in blunt trauma. In contrast, penetrating trauma can damage both the venous and arterial vasculature of the liver. Nonoperative management still has a role in select cases of penetrating trauma, especially when interventional radiology angioembolization can be utilized.^[11,12]

Nonoperative Management

Nonoperative management (NOM) is the treatment of choice in liver trauma for hemodynamically stable patients, regardless of the grade of injury.^[13,14] This is a paradigm shift away from operative management that has been evolving since the 1990s. Multiple studies have supported the successful treatment of hepatic injuries without surgery, with some retrospective studies reporting as high as >90% success rates.^[15]

Studies have also shown that bleeding due to liver injury can be worsened with operative intervention.^[16] NOM should include close monitoring in an intensive care unit when available, serial hematocrits, serial abdominal exams, and NPO status in the event an emergent procedure is needed. Additionally, facilities and personnel required for emergent surgical exploration should be available in case of clinical decline. Contraindications to NOM include hemodynamic instability, abdominal compartment syndrome, peritonitis, or absence of any of the previously listed observation elements.

Role of IR

Angioembolization has become an important adjunct to NOM of liver injuries in recent decades. There are currently no universally accepted guidelines regarding the role of angioembolization in hepatic injuries. However, several studies describe subsets of patients who might benefit from angioembolization.

Angioembolization is extremely successful at controlling hemorrhage when active extravasation of contrast is visualized on CT angiogram. It is also helpful when operative intervention fails as an adjunct tool. For example, when perihepatic packing via laparotomy is inadequate to control bleeding, angioembolization may be able to access the remaining active bleeds. In systematic reviews, angioembolization has been successful at controlling bleeding in over 70% of cases.^[17,18]

Surgical Management

In cases of hemodynamic instability despite initial resuscitation, in combination with signs of intraperitoneal hemorrhage demonstrated via FAST exam or other imaging, operative intervention is recommended. Surgery is also indicated in cases of failed NOM as evidenced by ongoing transfusion requirements and progression to hemodynamic instability.^[19]

The standard approach to these injuries should be through a midline laparotomy followed by evacuation of blood and 4-quadrant packing. If additional exposure is needed for an injury to the right lobe of the liver then the midline laparotomy can be “T-ed off” through a right subcostal extension.

Upon entering the peritoneum, bleeding may worsen initially since large volume hemoperitoneum provides a temporary tamponade effect. The surgeon should begin with manual compression of any obvious injuries to staunch active bleeding. This allows for evacuation of blood, better visualization, and time to resuscitate. Packing is the mainstay for treatment of liver injuries. It is particularly useful in remote settings to control bleeding until the patient can be transferred to an advanced trauma center.

Packing can be accomplished with laparotomy pads or the addition of hemostatic agents (e.g. combat gauze). Packs should be placed above, behind, lateral, and medial to the liver. The goal is to compress the liver back into its anatomic configuration. Sometimes this requires partial mobilization by taking down the falci and coronary ligaments, however, if you can avoid mobilization of the liver then do so because the ligaments can also help hold the configuration.

The surgeon should take great care to avoid injury to the IVC or hepatic veins when performing this step. It is also important to avoid excessive packing to the point of compressing the renal vasculature or IVC. One of the most effective techniques to control hepatic bleeding is to pack the liver as described above, place a temporary binder on the patient, and then proceed to IR for embolization. This allows time for adequate resuscitation and coagulation profiles to improve before going back to the OR later to remove the packs.

If there is ongoing bleeding despite packing, then a Pringle Maneuver can be attempted. The pringle can be done by compressing the porta hepatis between a finger and thumb, using a Rumel tourniquet or non-crushing clamp. This interrupts inflow of the hepatic artery and portal vein into the liver. This maneuver is both diagnostic and therapeutic. If bleeding ensues, the source is likely from another organ or from the hepatic outflow vessels – hepatic vein and inferior vena cava. If bleeding is controlled with this maneuver you have identified the source and can work to control the hemorrhage. The clamp should be released every 20-30 minutes to allow intermittent perfusion of the liver and avoid hepatic necrosis.^[1,11]

Additional hemostatic techniques to consider during the surgical management of liver injuries are as follows. Parenchymal injuries may be managed with direct suture closure with a large blunt-tipped needle. This is best for more superficial injuries that are clearly visualized. Blind deep suturing should be avoided to avoid injuring bile ducts or hepatic vessels. Deeper parenchymal injuries are better managed with the placement of surgical clips where hepatic vessels can be identified. Omental packing is often better than direct suture or clip placement. This can be done by mobilizing the omentum from the transverse mesocolon and then from the greater curvature of the stomach while preserving the gastroepiploic pedicle.

This “tongue” of omentum is then packed within the liver parenchyma. This is a superior technique in many cases because it uses well vascularized tissue with plenty of macrophage activity to fill the dead space, allowing for the greatest hemostatic effect. Penetrating liver injuries (e.g. deep knife or bullet wounds) pose a particularly difficult situation due to the formation of a tract that is usually difficult to access and difficult to pack. Peripheral tract injuries can be managed via tractotomy with a stapler or electrocautery bipolar vessel sealer (i.e. LigaSure). Sequential firing of the stapler or bipolar device along the tract provides hemostasis and exposes the deeper injuries previously hidden from view.

Central tract injuries are better managed with a balloon tamponade in which a balloon catheter such as Foley catheter, Sengstaken tube, or Blakemore tube is placed within the tract and inflated. There are rare cases in which injury is severe enough to warrant nonanatomic liver resection. Nonanatomic resection is used in cases of persistent bleeding, devitalized liver parenchyma, and major bile leaks. In general, resection is avoided due to very high rates of mortality. In the most severe cases, hepatic transplantation may be pursued if the patient is able to survive long enough to receive the organ. Regardless of surgical technique used, closed suctions drains should be placed for all high grade injuries.^{[2,20, 21]}

Retrohepatic IVC injuries

If packing and Pringle maneuver fail, then bleeding is likely from an aberrant hepatic artery anatomy or a retrohepatic IVC injury. Despite recent surgical advances, injuries to the inferior vena cava (IVC) continue to have extremely high mortality rates, ranging from 33-75%. ^[22] This high mortality rate is due to the fact that the vessel is fixed underneath the liver, making it difficult to access and control. Injury to the IVC is suspected when the Pringle maneuver is employed and bleeding from behind the liver continues (Figure 3).

Management principles for injury in this area include packing, additional exposure to gain better control, direct repair, and shunting. If there is a stable/non-expanding hematoma behind the liver, the surgeon should avoid exploration of this area even in penetrating trauma. Two specific techniques that can be implemented to address injuries in this area include total hepatic isolation and atriocaval shunt placement (Figure 4).

The former involves placing four clamps for vascular control on the aorta, Pringle maneuver, infrahepatic and suprahepatic IVC. The latter involves placing a large bore chest tube or ETT through the right atrial appendage and down the IVC past the injury.

Complications

Given the advances in trauma treatment and interventional radiology, blunt liver trauma is most commonly treated successfully with NOM. Because of this, various late complications have become emerging challenges.^[24] The rate of complications resulting from low-grade liver injuries is 0-7% while the rate of complications resulting from high-grade liver injuries is 11-13%.^[25] These include early or late liver hemorrhage, bile leak/biloma/biliary fistula, AV fistula, pseudoaneurysm,  liver abscess, and ischemic necrosis most commonly. We recommend routinely performing interval CT scans for high-grade injuries that are managed operatively or non-operatively.

Injury to extrahepatic biliary ducts

Injury to the extrahepatic biliary tree and gallbladder is the most common sequelae of liver trauma and can be seen in 13% of patients.^[26] Blunt injury usually results in avulsion of the biliary tree in areas where the bile duct is fixed to its surroundings or complete transection. Penetrating injuries often lead to partial transection.^[2] Clinical presentation can occur 7-10 days after injury and may include symptoms such as right upper quadrant pain, jaundice, fever, or melena.^[27]

If there is concern for a ductal injury, then intra-operative cholangiography is a useful adjunct. Injuries to the GB are typically managed with a cholecystectomy. Complete transection of the CBD should be repaired with Roux-en-Y hepaticojejunostomy. Partial CBD injuries can be repaired primarily, usually over a T-tube. These are often small ducts in young, healthy trauma victims and significant stricture is very common with primary repair. If the patient is severely unstable, then a damage control approach to a severe CBD injury involves ligation of the duct followed by reconstruction at the take-back operation.

Liver Abscess

Liver abscess after liver trauma is rare, with an incidence rate of 1.5%. It is usually seen with major liver injuries (grade 3 or above) and usually presents itself within 12 days (median of 6 days. Liver abscesses are mostly commonly bacterial in origin and management may be by surgical or percutaneous drainage and antibiotics.^[28,29]

Ischemic Necrosis

Ischemic necrosis following trauma is a relatively rare complication given the extensive blood supply to the liver and is almost always due to arterial injury or after angioembolization.^[30] Sudden disruption of intrahepatic blood supply allows for less opportunity for collateral circulation to perfuse the liver than hepatic artery injury because of simultaneous injury to the portal venous supply. The injury pattern is usually segmental and most patients recover without the need for liver resection, however, large-scale necrosis can lead to fulminant liver failure.^[31]

Summary

• The AAST Liver Injury Scale provides a systematic way to grade severity of liver injuries
• Majority of traumatic liver injuries are managed non-operatively and packing is the mainstay for treatment
• Operative intervention is indicated if a patient becomes hemodynamically unstable despite adequate resuscitation
• Avoid packing so tightly that the IVC is compressed and venous return to the heart is impeded
• Avoid exposure and exploration of stable retrohepatic hematomas, even in penetrating trauma
• Pringle maneuver is helpful when bleeding is not controlled with packing alone
• The vast majority of hepatic injuries that require laparotomy can be managed with a combination of damage control, electrocautery, packing, hemostatic agents and drainage
• The combination of damage control liver packing with angioembolization can be very effective for high-grade liver injuries.
• Common indications for angioembolization are active blush seen on CT angiogram and failure to control bleeding with damage control laparotomy
• A retrohepatic IVC injury is one of the most challenging injuries in all of trauma with an incredibly high mortality rate.

References

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