Dr. Shanmuganathan and Dr. Mirvis are with the Department
of Diagnostic Radiology, University of Maryland Medical Center
and Maryland Shock-Trauma Center, Baltimore, MD. Dr. Chen is
with the Department of Radiology, National Yang-Ming University
and Veterans General Hospital, Taipei, Taiwan.
The availability of fast conventional or spiral scanning, close
access to CT from adjacent patient admitting areas, and facilities
to monitor critically ill patients in the CT scanning suites, has
made CT scan the imaging modality of choice for definitive
evaluation of hemodynamically stable patients following blunt
trauma. Many studies have shown contrast- enhanced CT (CECT)
provides essential information for patient triage and management
including accurate localization of the extent and site of hepatic
injury, quantification of hemoperitonium, depiction of other
associated intra- and extraperitoneal injuries resulting from blunt
CECT can also document injury healing or progression, and
demonstrate early and late complications of hepatic trauma. While
CECT is the principal imaging modality used at our trauma center to
acutely assess the site and extent of hepatic injury, appropriate
application of other modalities including sonography, angiography,
and nuclear scintigraphy may play a role in diagnosing and managing
Studies comparing the outcome of patients with hepatic injury
managed without surgery and a control group of patients with
surgically managed liver injuries show no difference in the length
of hospital stay between the two groups. However, transfusion
requirements and intra-abdominal complications were significantly
lower in the group treated without surgery.
Surgical literature also confirms that up to 67% of celiotomies
performed for blunt trauma are unnecessary or nontheraputic, and
86% of the hepatic injuries have stopped bleeding at the time of
Hence, over the last decade trauma surgeons have moved from the
traditional approach of early surgical intervention to nonoperative
management of blunt liver injury.
CECT not only provides accurate information regarding the grade
of liver injury and the amount of hemoperitonium, it also reliably
and consistently detects the presence of other solid organ,
hollow-viscus, and mesenteric injuries. By providing this
constellation of information required to manage hemodynamically
stable blunt hepatic injuries without surgery, CECT has played a
major role in convincing trauma surgeons to widely accept and
promote this method of treatment over the last 5 years.
This article will discuss the contrast-enhanced spiral CT (CESCT)
findings of blunt hepatic injuries and its role in nonoperative
management of liver injuries.
CT scanning technique
Currently, our trauma center uses a spiral CT (Siemens Plus 4,
Siemens Medical Systems, Iselin, NJ) to evaluate the abdomen and
pelvis of trauma patients. Spiral CT scans are performed with 8-mm
collimation and a table speed of 8 mm/sec (pitch of 1). The abdomen
is scanned from the lower chest to the iliac crest and the pelvis
and then from the iliac crest to the pubic symphysis. A 100 to 120
sec delay between the abdominal and pelvic scans facilitates
visualization of contrast excretion in the lower ureters and
bladder. Conventional CT can be performed with ¾ 2.0 sec scan and
10-mm slice collimation at 10-mm table increments from the lower
chest to the iliac crest and 10-mm collimation at 20-mm table
increments from the iliac crest to the symphysis pubis. In our
center, intravenous (IV) contrast material (Omnipaque 240, Nycomed,
New York, NY), is power-injected (Mark-IV, Medrad, Pittsburgh, PA),
using a 150-mL bolus injection and infusion rate of 3 mL/sec for
spiral CT. For conventional CT, an initial bolus of 100 mL at a
rate of 1.5 to 2 mL/sec is followed by an infusion of an additional
50 mL at a rate of 1.0 mL/sec. Initiation of scanning is delayed 60
sec for spiral CT and 30 to 45 sec for convention CT after the
bolus infusion is started. All patients receive oral contrast
material consisting of 5 g of Hypaque powder (Nycomed, New York,
NY), in 300 mL of water 30 to 45 min before the scan, and if time
permits, a second dose is given either orally or via a nasogastric
tube when they arrive at the scanning suite.
Use of IV contrast material increases the conspicuity of
parenchymal injuries of the liver (figure 1) and helps to
demonstrate active bleeding throughout the abdomen and pelvis.
At our institution, IV contrast material is routinely administered
to all patients undergoing CT scans who do not have a known history
of major contrast allergies in order to optimize the difference in
attenuation between normal enhanced parenchyma of solid organs and
injured parenchyma or hematoma. Studies assessing optimal timing of
hepatic parenchymal enhancement for hepatic CT scanning have shown
that optimal enhancement varies with the volume and rate of
infusion of contrast material.
Recent advances in CT technology have led to development of very
fast conventional or spiral scanners that minimize misregistration
from patient motion and decrease volume averaging. Use of such fast
devices requires careful coordination of the initiation of contrast
opacification of the liver parenchyma and initiation of scanning.
Suboptimal enhancement of the liver parenchyma leading to
diminished CT sensitivity for hepatic injury detection can result
from early or delayed scanning, missing the peak of hepatic
parenchymal opacification, markedly aberrant hemodynamics affecting
systemic blood flow, or insufficient contrast material or iodine
Sites and mechanism of liver injury
The liver is the largest solid organ in the abdominal cavity and
is enclosed by the lower rib cage anteriorly and laterally. The
right lobe of the liver constitutes 80% of its volume, and it is
the most frequently injured region from blunt trauma. Of all
patients with blunt trauma to the abdomen, some 15% to 20% involve
Isolated injuries to the liver occur in less than 50% of blunt
The liver is incapable of achieving spontaneous hemostasis
because the hepatic veins lie within rigid canals and contract
Therefore, uncontrolled hemorrhage leading to exsanguination can
account for 46% to 80% of the mortality in grade IV and V hepatic
A variety of mechanisms have been proposed to explain hepatic
injuries. Injuries occur to the posterior right lobe from
compression against the fixed ribs, posterior abdominal wall, or
the spine. Contusion of the dome of the right lobe may result from
raised right thoracic cavity pressure propagated through the
diaphragm. The posterior abdominal wall can act as sites of shear
injury at the liver's attachment by the coronary ligaments to the
undersurface of the diaphragm, created by motion of the liver
relative to the rest of the body during rapid deceleration. Hepatic
injuries can also result from transmission of excessively high
venous pressure occurring at the time of impact to remote body
CT appearance of liver injuries
Numerous studies have shown CECT can accurately diagnose the
four principal types of liver injury shown by CT: hematoma(s),
laceration(s), vascular injuries, and active hemorrhage.
Many systems have been proposed to classify liver injuries. At our
institution, hepatic injuries are classified using the CT scan
classification of Mirvis et al (table 1)
that is based on the American Association for the Surgery of Trauma
(AAST) surgical grading scale (table 2).
This helps to compare treatment and outcome among patients with
liver injury from different trauma centers.
Single or multiple hematomas may be seen following blunt trauma.
Hepatic hematomas may be intraparenchymal and/or subcapsular
(figure 2). On unenhanced CT subcapsular hematoma is hyperdense
relative to normal liver parenchyma. On CECT subcapsular hematomas
are typically seen as a low attenuation lentiform collection of
blood between the liver capsule and the enhancing liver parenchyma
(figure 2). Subcapsular hematomas often compress the underlying
liver parenchyma; this CT finding helps to differentiate
subcapsular hematomas from small amounts of blood or fluid in the
perihepatic space. Uncomplicated subcapsular hema-tomas typically
resolve within 6 to 8 weeks and the attenuation value decreases
with age of the injury.
On CECT, acute hematomas appear as irregular high attenuation
areas of clotted blood surrounded by lower density non-clotted
blood, bile, or an area of parenchymal contusion (figure 3). With
healing, a hematoma develops smoother margins, expands in size, and
demonstrates gradual decrease in attenuation values until it
eventually appears as serous fluid collection.
Acute liver lacerations on CECT have sharp or jagged margins and
appear as linear or branching low attenuation areas (figure 4). A
compressive force may produce multiple parallel lacerations termed
"bear-claw" lacerations. Lacerations ¾ 3 cm in depth from the
surface can be classified as superficial, and >3 cm deep as deep
lacerations. Liver lacerations that extend into the region of one
or more of the major hepatic veins (figure 5) were associated with
an increased likelihood of a false negative CT for vascular injury,
an increased chance of postoperative hepatic hemorrhage, an
increase in delayed hepatic-based complications, and an increased
chance of failure of nonoperative treatment (PA Polettie, MD,
personal communication, September 1999). Unopacified portal or
hepatic veins, or dilated biliary ducts can mimic hepatic
lacerations with a branching pattern and need careful evalation of
serial images to differentiate the various structures.
As liver lacerations heal, the lesion enlarges, its margins
become smoother and assume a rounded to oval configuration on
follow-up CT. Unlike subcapsular hematomas, liver lacerations
persist for several months. These lesions may gradually decrease in
size with time or remain as a well-defined hepatic cyst.
Fortunately, injuries to the major hepatic veins or retrohepatic
vena cava (juxtahepatic venous injuries) are rarely seen following
blunt abdominal trauma. Retrohepatic vena caval injuries from blunt
trauma are typically associated with a very high mortality (90% to
100%). In most series, this high mortality has been attributed to
excessive blood loss and the inevitable coagulopathy resulting from
the long delay in recognizing that juxtahepatic venous injuries
were present, bleeding, and the difficulty in obtaining exposure to
repair these vascular injuries.
Retrohepatic vena caval injuries are suspected on CT on the basis
of liver lacerations extending into the major hepatic veins or
inferior vena cava; or profuse hemorrhage behind the right lobe of
the liver, into the lesser sac, or near the diaphragm (figure 5).
Prior suspicion of such vascular injuries can assist the surgeon in
planning the surgical approach, controlling hemorrhage, and
repairing the vascular injuries through vascular isolation
techniques requiring a combined thoracoabdominal approach. A
combined therapeutic approach for high-grade liver lacerations with
injury to the retrohepatic vena cava involves the trauma surgeon
and interventional radiologist. Initially, the trauma surgeon
attempts to control the massive hemorrhage by temporary perihepatic
packing. Recurrent hepatic parenchymal hemorrhage following liver
packing has been successfully managed using transcatheter
embolization of arterial sources of blood loss, with bleeding from
major hepatic veins controlled by intravenous stent placement.
Partial hepatic devascularization can result from an injury to
the blood vessels in the perihilar region by a deep laceration,
thrombosis of the major hepatic veins, or complete avulsion of the
dual blood supply of the liver. On CECT these fragments would be
seen as wedge-shaped regions extending to the periphery of liver
that fail to enhance (figure 6). The ability to scan during the
peak of contrast enhancement of the liver parenchyma with spiral CT
makes this scanning technique well suited to visualize
pseudoaneurysms or contrast extravasation from an injury to the
hepatic artery or its major branches. Hepatic vascular injuries may
result from hepatic lacerations extending across the major hepatic
arterial/venous branches, shearing forces, or excessive stretching.
CT can provide a clear indication whether or not to perform hepatic
On CECT active hemorrhage in the liver is seen as an irregular
area of contrast extravasation (figures 5 and 7). The significant
difference in the attenuation value of extravasated contrast
material (range 85 to 350 H, mean 132 H) and hematoma (range 40 to
70 H, mean 51 H) is helpful in differentiating active bleeding from
Studies performed at our institution to determine the value of CECT
in detecting active hemorrhage, showed that CT was a valuable
imaging modality to show the exact location of active bleeding and
help direct appropriate management.
CT is useful in evaluating ongoing or recurrent active bleeding
in the liver following surgical or angiographic intervention.
Extravasated contrast from a prior angiographic study can mimic
active hemorrhage by CESCT. Therefore, it is important to perform
both pre- and postcontrast CT scans of the liver in patients who
have recently had hepatic angiography to distinguish previously
extravasated angiographic contrast from ongoing hepatic bleeding.
Other parenchymal liver lesions that could mimic active bleeding on
CT include calcified liver lesions and contrast enhancement seen in
Periportal low density
Periportal low density refers to regions of low attenuation that
parallel the portal vein and its branches on CT (figure 8). Often,
periportal low density when seen alone in blunt trauma victims is
attributed to hemorrhage tracking along the periportal connective
tissues and believed to represent an important, if subtle, CT sign
of liver injury.
Macrander et al
reported periportal low density seen on CT in 62% of patients with
liver injury. However, studies performed by Patrick et al
in children with blunt abdominal trauma and at our institution
suggests that periportal low density without parenchymal liver
injury occurs as a result of an elevated central venous pressure
(CVP). This elevation results from vigorous IV fluid administration
prior to obtaining the CT scan or other trauma-related causes of
elevated CVP such as tension pneumothorax or pericardial tamponade
resulting in distension of the periportal lymphatic vessels.
This CT finding has been noted in several nontraumatic clinical
conditions including acute transplant rejection, malignant neoplasm
of the liver, liver transplantation, cardiac failure, and cardiac
tamponade and is usually attributed to dilatation of the
intrahepatic lymphatics from obstruction of the normal hepatic
lymphatic drainage. Periportal low density seen on CT without
evidence of parenchymal liver injury does not represent hepatic
injury and does not warrant hospital admission for observation or
follow-up CT. Focal periportal low density seen in close proximity
to a liver laceration may represent some focal hemorrhage
dissecting into the adjacent portal tracts.
Sonography in hepatic trauma
In the United States, sonography is mainly used for the
detection of hemoperitoeum as an indicator of intrabdominal
However, up to 34% of abdominal visceral injuries can occur without
hemoperitoneum and 17% of these patients require angiographic or
Sonography can be used to visualize parenchymal hepatic injuries
directly. The sensitivity to detect hepatic injuries or
hemoperitoneum depends to some extent on the quality of imaging
equipment, the conditions under which the study is performed, and
the level of experience and training of the operator. Hepatic
parenchymal injuries are commonly seen on sonography as discrete
hyperechoic area. Other sonographic patterns seen include a diffuse
hyperechoic liver parenchyma and a discrete hypoechoic focus in the
Published data report that sonography underestimated the severity
of liver injury in 52.8% of 36 patients and entirely missed the
lesion in 11% to 36% of the CT or surgically documented high grade
(Mirvis grade 3 or greater) hepatic injury.
If a hepatic injury is identified by sonography, it could be
potentially followed by this method to document resolution or
Angiography in hepatic trauma
Because of the dual blood supply of the liver subselective
embolization can be performed without risk. As a primary treatment
modality, transhepatic embolization has been used to improve
success in nonoperative management of stable patients with
high-grade liver injury.
Transcatheter embolization has been successfully used to treat
active bleeding, pseudoaneurysms, arterio-venous fistulas, and
Schwartz et al
reported their 11-year experience of transcatheter embolization for
controlling hemorrhage from hepatic injuries and found this
technique to be safe and effective in 21 of the 24 patients
included in their study. Angiographic embolization can be performed
independently or when surgery fails to control bleeding of hepatic
origin. At our institution, patients with CT evidence of active
hemorrhage in the liver who do not promptly respond to IV fluid
resuscitation are referred for urgent surgical or angiographic
CECT has revolutionized the diagnosis and management of patients
with liver trauma. Information provided by CT allows for
determination of the extent of liver injury and identification of
other nonhepatic abdominal injury. This information, coupled with
clinical assessment and interventional angiography, can be used to
optimize management of all grades of hepatic injury.
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