eMedicine Specialties > Radiology > Gastrointestinal

Liver, Trauma: Imaging

Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, Consultant Radiologist and Honorary Professor, North Manchester General Hospital Pennine Acute NHS Trust, UK
Coauthor(s): Hemant Vadeyar, MBBS, Consulting Hepatobiliary and Pancreatic Surgeon, North Manchester General Hospital; Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute; Muthusamy Chandramohan, MBBS, DMRD, FRCR, Consultant Radiologist, Bradford Teaching Hospitals, UK
Contributor Information and Disclosures

Updated: Aug 25, 2009

Radiography

Findings

Plain radiographic findings are nonspecific, but they are useful in evaluating rib and spinal injuries in patients with blunt abdominal trauma. Fractures of the right lower ribs should suggest the possibility of underlying liver injury. Pneumoperitoneum, major diaphragmatic injury, gross organ displacement, and metallic foreign bodies may be identified.¹⁴

Degree of Confidence

Plain radiographs are sensitive and specific in demonstrating skeletal injuries and usually are the first radiologic examination performed in patients in whom liver trauma is suspected. Radiographs may initially depict opaque foreign bodies, such as bullets or shrapnel.

False Positives/Negatives

Because plain radiography is performed in a traumatized patient, an optimal-quality radiograph is not always possible. Fractures and a pneumoperitoneum may be missed.

Computed Tomography

Findings

CT scanning, particularly contrast-enhanced CT scanning, is accurate in localizing the site and extent of liver injuries and associated trauma, providing vital information for treatment in patients.^10,11 Spiral CT scanning is the preferred scanning technique, if available. Multidetector-row CT scanning offers the further advantages of fast scanning times (allowing scanning during specific phases of intravenous contrast enhancement) and the acquisition of thin sections over a large area (allowing high-quality multiplanar reconstruction).¹⁵ CT scanning without intravenous contrast enhancement is of limited value in hepatic trauma, but it can be useful in identifying or following up a hemoperitoneum.

CT scans can be used to monitor healing. Trauma to the liver may result in subcapsular or intrahepatic hematoma, contusion, vascular injury, or biliary disruption.¹⁶ CT scan criteria for staging liver trauma based on the AAST liver injury scale include the following:

• Grade 1 - Subcapsular hematoma less than 1 cm in maximal thickness, capsular avulsion, superficial parenchymal laceration less than 1 cm deep, and isolated periportal blood tracking (See Images below and Images 1 and 2 in Multimedia)

• Grade 2 - Parenchymal laceration 1-3 cm deep and parenchymal/subcapsular hematomas 1-3 cm thick (See Images below and Images 5-8 in Multimedia)

• Grade 3 - Parenchymal laceration more than 3 cm deep and parenchymal or subcapsular hematoma more than 3 cm in diameter (See Images below and Images 12 and 13 in Multimedia)

• Grade 4 - Parenchymal/subcapsular hematoma more than 10 cm in diameter, lobar destruction, or devascularization (See Images below and Images 15, 16, and 18-21 in Multimedia)

• Grade 5 - Global destruction or devascularization of the liver (See Images below and Images 24-27 in Multimedia)

• Grade 6 - Hepatic avulsion

CT scan findings include the following:

• Subcapsular hematoma
  • This is usually seen in a lenticular configuration; most subcapsular hematomas are anterolateral to the right lobe of the liver.
  • Subcapsular hematomas cause direct compression and deformity of the shape of the underlying liver.
  • On nonenhanced CT scans, the liver appears hyperattenuating compared with a subcapsular hematoma.¹⁷
  • On enhanced CT scans, a subcapsular hematoma appears as a low-attenuating, lenticular collection between the liver capsule and the enhancing liver parenchyma.
  • Unless bleeding recurs, attenuation of the subcapsular hematoma decreases with time. Subcapsular hematomas resolve within 6-8 weeks.
• Intraparenchymal hematomas
  • On contrast-enhanced CT scans, acute hematomas appear as irregular, high-attenuation areas, which represent clotted blood, surrounded by low-attenuating unclotted blood or bile.
  • Over time, the attenuation of the hematoma is reduced, and the hematoma eventually forms a well-defined serous fluid collection that may expand slightly.
  • A focal, intrahepatic, hyperattenuating area with attenuation of 80-350 HU may represent an active hemorrhage or pseudoaneurysm.
  • Focal or diffuse periportal low attenuation is believed to be secondary to tracking of blood around the portal vessels, although other possibilities include bile leaks, edema, and dilated periportal lymphatics resulting from increased central venous pressure or injury to the lymphatics.
  • A low-attenuating periportal collar is seen in children with nonhepatic blunt abdominal trauma and also in the absence of intra-abdominal injury. Thus, without other ancillary findings within the liver, the presence of a low-attenuating periportal collar is not indicative of hepatic injury. However, the presence of this sign in documented abdominal trauma correlates with the severity of trauma, physiologic instability, and a higher mortality rate.
  • CT scan findings in approximately 25% of children with blunt abdominal trauma show periportal low attenuation. That only 40% of these children have evidence of liver injury has been shown.
• Laceration
  • Laceration of the liver appears as a nonenhancing linear or branching structure, usually at the liver periphery.
  • Acute lacerations have a sharp or jagged margin, but with time, lacerations may enlarge, and the margins may develop rolled edges.
  • Multiple parallel lacerations occur as result of compressive forces (bear claw lacerations).
  • Lacerations may communicate with hepatic vessels and/or biliary radicles.
• Vascular injuries
  • Injuries to the major hepatic veins and the retrohepatic inferior vena cava are uncommon after blunt abdominal trauma.
  • Retrohepatic vena caval injuries are suggested on CT scans when lacerations extend into the major hepatic veins and the inferior vena cava or when profuse retrohepatic hemorrhage extends into the lesser sac or near the diaphragm.
  • Perihilar liver tissue may become partially devascularized by a deep laceration or complete avulsion of the dual hepatic blood supply. These devascularized areas of the liver appear as wedge-shaped regions extending toward the liver periphery, and they fail to enhance after the administration of contrast material.
  • Pseudoaneurysms are better depicted by using spiral or multisection CT scanning because of the ability to image during peak contrast enhancement.
• Acute hemorrhage
  • Acute, intrahepatic hemorrhage is seen as irregular areas of contrast agent extravasation.
  • Measurement of attenuation values is useful in differentiating extravasated contrast from hematoma. Extravasated contrast material has an attenuation value of 85-350 HU (mean, 132 HU), whereas hemorrhage has an attenuation value of 40-70 HU (mean, 51 HU).
  • CT scans can be useful in depicting recurrent bleeding after surgery or radiologic intervention.
• Gallbladder injury
  • Gallbladder injury is uncommon, occurring in 2-8% patients with blunt liver trauma. Prior to the availability of CT scanning and ultrasonography, gallbladder injuries were rarely diagnosed before surgery.¹⁸
  • CT findings in gallbladder injuries include ill-defined or irregular wall contour, pericholecystic or subserosal fluid, collapsed gallbladder, wall thickening, intraluminal blood, free intraluminal mucosal flap, contrast enhancement of the gallbladder wall or mucosa, free intraperitoneal fluid iso-attenuating with bile, mass effect on the duodenum, and displacement of the gallbladder toward the midline.
• Biloma and bile peritonitis
• Biloma
  • As a result of the slow rate of leaking, a biloma may take weeks or months to develop after trauma; hence, it usually is diagnosed by using follow-up scans.
  • CT scan findings of a posttraumatic biloma demonstrate a cystic structure of low attenuation in or around the liver.
  • Bilomas may contain debris or septa.
  • Bile peritonitis is an uncommon complication of blunt liver trauma. CT scan findings of bile peritonitis include persistence or increasing amounts of low-attenuating, free peritoneal fluid and thickening of a peritoneum that shows evidence of enhancement.

Degree of Confidence

CT scanning is the mainstay of diagnosis of hepatic injuries following blunt trauma; initial CT scan findings help in determining the type of treatment required. With the use of high-speed, spiral CT scans, predicting the necessity of operative treatment or angiography is possible in patients with blunt hepatic injury before deterioration of their hemodynamic state.

A finding of pooled contrast material within the peritoneal cavity indicates active and massive bleeding; patients with this finding may require emergency surgery.¹⁹ Intrahepatic pooling of contrast material with an intact liver capsule usually indicates a self-limiting hemorrhage; most patients with this finding can be treated conservatively.

CT scanning has been proven to be extremely useful in helping to make therapeutic decisions in hepatic trauma and in helping to reduce laparotomy rates in as many as 70% patients at the time of initial evaluation.

False Positives/Negatives

False-positive errors in the diagnosis of liver injury with CT scans may occur as a result of beam-hardening artifacts from adjacent ribs, which can mimic contusion or hematoma. An air-contrast level within the stomach in a patient with a nasogastric tube can produce streak artifacts throughout the left lobe of the liver; these may mimic intrahepatic lacerations and/or hemorrhage. The nature of these artifacts can be confirmed if the patient is scanned in a decubitus position.

False-negative findings may occur in the setting of a fatty liver only when contrast-enhanced CT scans are obtained. On these images, the enhanced fatty liver may become iso-attenuating relative to the laceration or hematoma. In this situation, a nonenhanced CT scan may provide useful information regarding hepatic injury. Focal fatty infiltration may also mimic hepatic hematoma, laceration, or infarction. Hepatic lacerations with a branching pattern can mimic nonopacified portal or hepatic veins or dilated intrahepatic bile ducts. Careful evaluation of all branching intrahepatic structures is important, and the diagnosis is made with serial images to differentiate the various structures.

Small amounts of free intraperitoneal blood or fluid in the perihepatic space may mimic a subcapsular hematoma; however, these fluid collections usually do not compress the liver parenchyma. CT scans do not always help in predicting which patients require laparotomy.²⁰ Hematomas or hemorrhage within the liver can occur with a nontraumatic etiology (see Ultrasonography).

In the evaluation of recurrent hepatic bleeding, particularly after an angiographic intervention, nonenhanced and enhanced scans are important to distinguish extravasated contrast material during angiography from recurrent, ongoing hemorrhage. Other hepatic lesions that may mimic active bleeding on CT scans include calcified liver masses and hemangiomas.

Magnetic Resonance Imaging

Findings

MRI has a limited role in the evaluation of blunt abdominal trauma, and it has no advantage over CT scanning. Theoretically, MRI can be used in follow-up monitoring of patients with blunt abdominal trauma, and the modality may be useful in young and pregnant women with abdominal trauma in whom the radiation dose is a concern.²¹

MRCP has been used in the assessment of pancreatic duct trauma and its sequelae, and it can be used to image biliary trauma.¹² Another potential use of MRI is in patients with renal failure and in patients who are allergic to radiographic contrast medium.

Degree of Confidence

MRI offers no significant advantage over CT scanning for routine evaluation of acute abdominal trauma. Experience is insufficient for assessing the value of the above-mentioned special circumstances.

False Positives/Negatives

Sufficient experience has not been gained in the use of MRI to establish false-positive and false-negative findings.

Ultrasonography

Findings

• Ultrasonograms can demonstrate a number of traumatic lesions, such as hematomas, contusions, bilomas, and hemoperitoneum.²²
• Hepatic hematomas are grouped into 3 categories, as follows:
  • Rupture into the liver and its capsule
  • Separation of the capsule by a subcapsular hematoma
  • Central hepatic ruptures
• A subcapsular hematoma usually appears as a curvilinear fluid collection; its echogenicity varies with age.
  • Initially, hematomas are anechoic, becoming progressively more echogenic over the course of 24 hours.
  • With the passage of time, echogenicity of the hematoma once again begins to decrease, and within 4-5 days, the hematoma becomes hypo-echoic or anechoic.
  • Septa and internal echoes often develop within the hemorrhagic collection by 1-4 weeks.
• Appearances of hepatic laceration change with time. Lacerations appear slightly echogenic, becoming hypo-echoic or cystic when scanned days after the injury.
• Similar to hematomas, contusions usually are hypo-echoic initially, becoming transiently hyperechoic and then hypo-echoic.
• The most common ultrasonographic pattern observed with liver parenchymal injuries is a discrete hyperechoic area; however, a diffuse hyperechoic and occasionally a discrete hypo-echoic pattern may be observed.^17,22
• An echogenic clot often is seen surrounding the liver, and hypo-echoic fluid may be observed in other parts of the abdomen.
• Bilomas appear as rounded or ellipsoid, anechoic, loculated structures that are fairly well defined in close proximity to the liver and bile duct.
• Diaphragmatic ruptures appear as a discontinuous line of echoes.
• A number of studies have suggested that ultrasonography can replace the invasive procedure of peritoneal lavage in the evaluation of blunt abdominal trauma.

Degree of Confidence

Focused assessment performed by using ultrasonography in patients with liver trauma is still investigational for evaluation of blunt and penetrating abdominal trauma.²³ The primary advantage is immediate availability in emergency departments. Some centers use ultrasonography as the initial examination. Patients who are unstable and have a large amount of fluid detected on ultrasonograms are immediately transported for surgery. In addition, patients at these centers who are stable and who have a large amount of intra-abdominal fluid also may be immediately treated with surgery.

An alternative approach is followed in other centers. If ultrasonographic findings are positive for intra-abdominal fluid, CT scanning is the next step. If fluid is not demonstrated on abdominal ultrasonograms, the patient is observed for 12 hours; however, if abdominal pain persists, the patient undergoes CT scanning.

Ultrasonography is the initial examination of choice in the pediatric age group because of the modality's nonionizing and noninvasive nature. Ultrasonography is particularly useful in imaging neonates who are ill and in whom the clinical condition is too unstable to allow transport to a CT scanning facility but who may have a hepatic hematoma after a traumatic delivery or resuscitative efforts. In a neonate with a decreasing hematocrit level and increasing abdominal distension, ultrasonography may rapidly help in confirming a diagnosis of liver trauma. Because most children with hepatic trauma are treated conservatively, most children can be monitored by using ultrasonography.^8,24

Ultrasonography has several advantages over peritoneal lavage in the diagnosis of blunt abdominal trauma. Ultrasonography is a noninvasive procedure that is readily available at the patient's bedside and is less expensive to perform than is peritoneal lavage. However, although ultrasonography may be useful in most patients with blunt abdominal trauma, pitfalls remain.

False Positives/Negatives

Injury to the liver, especially at the dome or lateral segment of the left lobe of the liver, can easily be missed with ultrasonography, particularly in the presence of ileus or when pain makes the examination difficult. The sensitivity of ultrasonography in the detection of free abdominal fluid associated with bowel or mesenteric injury has been reported as only 44%. Blunt abdominal injury may involve organs other than the liver, and these injuries must be detected reliably.

Ultrasonograms may not directly depict injuries to the bowel, mesentery, pancreas, diaphragm, adrenal gland, and bone. Ultrasonography is probably limited in the detection of many vascular injuries as well. A hepatic laceration may be initially difficult to detect, but it may become obvious with the passage of time.

Hepatic hemorrhage may occur as a result of causes other than trauma, including sickle cell anemia, liver tumors, coagulopathies, organ phosphate toxicity, and collagen vascular disease. It may also occur in patients receiving long-term hemodialysis. Hepatic hemorrhage and rupture may occur in eclampsia, pre-eclampsia during the third trimester of pregnancy, HELLP syndrome, hepatic adenoma, and hepatocellular carcinoma.

Nuclear Imaging

Findings

• Patients who have documented evidence of hepatic or splenic trauma can be monitored noninvasively by using^99m Tc sulfur colloid scanning. Most patients with liver trauma show complete or partial resolution of the colloid defects over a period of 3-6 months. However, defects within the spleen may persist indefinitely and do not necessarily indicate a poor prognosis. Whether defects in the liver have similar connotations is uncertain.
• After splenic rupture, splenic tissue can become implanted in the peritoneal or intrathoracic cavities (splenosis). Splenosis may be difficult to differentiate from other masses, such as lymphadenopathy, on subsequent scans obtained by using cross-sectional imaging, particularly when scans are performed remote in time from the injury. Uptake with^99m Tc sulfur colloid or^99m Tc-labeled denatured red cells provides a tissue-specific diagnosis of ectopic splenic tissue.
• Labeled red cells may be used to detect the site of active intraperitoneal or retroperitoneal hemorrhage, although quantitating the size of the hemorrhage is difficult using this technique.
• Bile duct and/or gallbladder injuries occur in 5% of patients with blunt abdominal trauma. Moreover, biliary injuries may not be identified pre-operatively or may remain unidentified for weeks or months after trauma.
• Although CT scanning remains the examination of choice in the evaluation of liver trauma, the procedure of choice to evaluate bile leaks is^99m Tc IDA scanning. CT scanning and ultrasonography can help to detect intra-abdominal fluid, but differentiation between loculated ascitic fluid and hematoma, abscess, and biloma may not be always possible.
  • Scanning for^99m Tc IDA uptake usually is performed as a dynamic study immediately after the injection of the radionuclide. The angiographic phase can provide important information regarding vascular injuries and associated renal injury, which may subsequently be missed on static scans.
  • Following the dynamic study, a 20-min static scan of the liver is obtained in several planes; in appropriate circumstances, scans can be obtained for as long as 24 hours.
  • Bile leaks are demonstrated as extravasated activity shortly after administration of the radionuclide.
  • Bilomas are demonstrated initially as a photon-deficient mass that shows activity on delayed scans. In the detection of bilomas, delayed images are essential (2-24 h); otherwise bilomas may be missed.

Degree of Confidence

In patients with blunt trauma, there is an inability to evaluate other sites of abdominal injury and to quantitate intraperitoneal and retroperitoneal hemorrhage. However, in patients in whom a bile leak or biloma is suspected,^99m Tc IDA uptake imaging is the examination of choice; this provides a noninvasive technique for arriving at a specific diagnosis.

False Positives/Negatives

Focal defects identified with^99m Tc sulfur colloid scanning or in the angiographic/hepatic phase of^99m Tc IDA scanning may not be related to the trauma; these defects may instead represent simple liver cysts, granulomas, pseudotumors, abscesses, or tumors unrelated to trauma. If delayed scans are not performed, bilomas and bile leaks may be missed using^99m Tc IDA scans. Delayed imaging not only provides time for the activity to accumulate within the biloma but also allows clearing of the isotope from the liver, increasing the target-to-background ratio of activity.

Angiography

Findings

Angiographic findings in patients with liver trauma include the following:

• Liver contusion
  • Stretching and elongation of arterial branches around an avascular mass may be observed.
  • Delay in hepatic blood flow to the involved segments may occur.
  • A transient attenuation difference in uninvolved segments may be depicted.
  • Mottled accumulation of contrast material in the parenchymal phase may be noted.
  • The portal venous phase may confirm a parenchymal defect.
  • Peripheral portal venous filling may be unusually well demonstrated in the presence of contusions.
• Liver lacerations
  • Arterial collaterals may bypass arterial occlusions.
  • Contrast material extravasation may occur.
  • Discrete lacerations may appear as linear or complex lucent defects.
  • Intrahepatic hematomas may appear as poorly defined lucent defects.
  • Arterioportal fistulas may be obvious.
  • Contrast material may pass into the biliary tree, identifying the site of hemobilia.
• Subcapsular hematoma
  • Subcapsular hematomas compress normal parenchyma and may appear as sharply defined, lucent defects against the increased contrast accumulation in the compressed parenchyma.
  • Arterial displacement may be seen.
  • Contrast material extravasation may occur.
• High-velocity bullet injuries
  • High-velocity bullets tend to cause burst injuries with distant contusions and parenchymal disruption.
  • Occasionally, these injuries are associated with aortic and renal injuries.
  • All of the angiographic findings of blunt liver trauma can be seen in this group of patients.
• Low-velocity penetrating injury (stab wounds, liver biopsy, and biliary drainage TIPS procedure)
  • Arterial aneurysms and arterial pseudo-aneurysms
  • Arteriovenous fistulas
  • Hematomas

Degree of Confidence

Evaluating the extent of liver injury at surgery may be difficult; in fact, identifying the lesion within the liver may occasionally be impossible. Emergency hepatic angiography should be performed if at all feasible, because it not only documents the injury and helps to evaluate complications, such as pseudo-aneurysms, subcapsular hematoma, or hemobilia, it also provides access for transcatheter embolization.

False Positives/Negatives

Although angiography is useful in selected patients, false-positive and false-negative results occur in patients with hepatic trauma.

Liver rupture may be spontaneous or may occur as result of liver tumors, HELLP syndrome, simple cysts, amebic abscess, and hydatid cysts. Intrahepatic arterial aneurysms may be congenital or may be related to vasculitides.

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