Imaging of Abdominal Trauma

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Imaging of Abdominal Trauma
Rathachai Kaewlai, MD
Ramathibodi Hospital, Mahidol University, Bangkok
Emergency Radiology Minicourse 2013
Slides available at RiTradiology.com or Slideshare.net/rathachai



Introduction
•  Abdominal injuries common in multiply-
injured patients (20%-40%)
•  High death rate, similar to head trauma
•  Can be blunt or penetrating
– Blunt compressive or deceleration forces
– Penetrating: shrapnel, gun shot, blast



Introduction
•  Different forces  different types of injuries
– Deceleration force  vessel injuries
– Compression force  “package” injuries
•  Each organ reacts differently to forces
– Solid organs lacerate, contuse, infarct
– Hollow organs perforate



Potential Means to Assess
Abdominal Injuries
•  Physical examination: poor sensitivity (<50%)
•  Diagnostic peritoneal lavage (DPL): now obsolete
owing to limited accuracy and invasiveness
•  Imaging has already replaced DPL
–  Ultrasound (FAST): hemoperitoneum
–  CT: hemoperitoneum, solid/hollow viscus injuries, active
extravasation/vascular injuries



“Abdomen”
•  Anterior: nipple line to groin crease
•  Posterior: tips of scapulae to gluteal
skin crease
•  Three basic regions of abdomen
–  Peritoneal cavity + intrathoracic
component
–  Retroperitoneum
–  Pelvis



Blunt Abdominal Trauma
•  Motor vehicle collision (MVC, ~75%),
motorcycle crashes (MCC), pedestrian-
automobile impacts, falls and assaults
•  Multiple different organ injuries
•  Major complications: peritonitis,
hemorrhagic shock and death
•  Two categories:
– Solid organ injuries
– Hollow organ injuries



Blunt abdominal trauma evaluation
Hemodynamically stable Hemodynamically unstable
FAST
CT
FAST/DPL
Positive Negative
Laparotomy
Positive Negative
Positive Negative
Search for other sources
of hemorrhage
Consider discharge
Minor injury
Observation
Major, nonoperative
ICU observation
Operative
Laparotomy
Observation
Repeated FAST
CT



Penetrating Abdominal Trauma
•  Foreign object pierces skin. Gunshot wounds (GSW),
stab wounds
•  External appearance of penetrating wound does NOT
determine extent of internal injuries
•  Define trajectory of penetrating wound and consider all
possible internal injuries
•  Complications: hemorrhagic shock
•  Organs injured: penetrating > blunt trauma = SB, colon/
rectum, stomach, pancreas, diaphragm



Penetrating abdominal trauma evaluation
Hemodynamically stable Hemodynamically unstable
Laparotomy FAST
Positive Negative
Stab Wound GSW
To Back/ﬂank – CT indicated
Anterior – CT considered
Thoracoabdominal – CT considered
Shotgun to back/ﬂank – CT indicated
Shotgun to anterior – Laparoscopy/otomy
Bullet (higher velocity) – Laparotomy



Focused Assessment with
Sonography for Trauma (FAST)
•  Been used for over 30 years
•  Bedside screening to aid clinicians in identifying
free fluid in thorax or abdomen
•  Initially designed to focus primarily on detection
of free fluid – now modified to detect
pneumothorax, quantification of fluid
•  Sensitivity 80-90%, specificity 95-100% for free
fluid



Anatomical Considerations
•  Site of fluid accumulation depends on
position of patient and source of bleeding
•  Free fluid in dependent compartments
–  RUQ  Morison’s pouch  right paracolic gutter 
pelvis
–  LUQ  subphrenic space  splenorenal recess 
left paracolic gutter  pelvis
–  Pelvis = rectovesical pouch (M), pouch of Douglas (F)



Scanning Techniques
•  Sequential
– Pericardium
– Perihepatic
– Perisplenic
– Pelvis
•  Standard or microconvex probe
•  Transthoracic view follows standard



FAST
PERICARDIUM
•  Global cardiac
function
•  Chamber size
•  Normal pericardium =
white line surrounding
heart
•  Sweeps anterior-
posterior
PERIHEPATIC
•  Right pleural effusion,
free fluid in Morison’s
pouch, free fluid in
paracolic gutter
•  Mid-axillary line
between 8th-11th ribs
with oblique scanning
plane



FAST
PERISPLENIC
•  Left pleural effusion, free
fluid in subphrenic space
and splenorenal recess,
free fluid in left paracolic
gutter
•  Left diaphragm, spleen,
left kidney
PELVIC
•  Longitudinal and
transverse views
•  Free fluid in anterior
pelvis or cul-de-sac
•  Ideally should be done
before Foley
•  Differentiate partially filled
bladder with free fluid by
–  Emptying bladder (Foley)
or
–  Retrograde bladder filling



Hemopericardium
•  Anechoic stripe surrounding the heart within parietal
and visceral layers of bright hyperechoic pericardial sac
•  Especially helpful in penetrating trauma
•  Classic clinical signs found in < 40% of cases with
proven cardiac tamponade
•  Bedside cardiac US
–  Reduces time of diagnosis and disposition to OR
–  Increases survival
•  Sensitivity 100%, specificity 96.9%, accuracy
97.3%



Free Pleural Fluid
•  Anechoic stripe above diaphragm
•  US is at least comparable to CXR
•  Minimum fluid needed
–  Upright CXR 50-100 mL
–  US 20 mL
•  Differentiation of fluid from pleural thickening and
lung contusion
•  Complement CXR in diagnosis of hemothorax in
supine patient



Hemoperitoneum
•  Anechoic stripe in
Morison’s pouch,
paracolic gutter,
splenorenal recess,
left subphrenic space,
pelvis



US Features of Organ Injuries
•  Not specific goal of FAST to detect organ injury
•  Acute laceration
–  Fragmented areas of increased or decreased echo
•  Contained intraparenchymal or subcapsular
hemorrhages
–  Isoechoic or slightly hyperechoic (difficult to detect)
•  Low sensitivity esp splenic injury



Pitfalls of FAST
•  Contraindication (when emergent Sx
needed)
•  Overreliance on FAST: esp negative ones
•  Limitations of FAST:
– Morbidly obese
– Massive subcutaneous emphysema
•  Pregnancy
•  Technical difficulties



How FAST Affects Other
Diagnostics
•  Reduce number of DPL
•  Reduce number of CT
•  No change to patient’s risk
•  Cost saving
Unboundedmedicine.com
Wired.com



Detection of Pneumothorax
•  Pneumothorax occult on CXR in 29-72%
•  Extended FAST (EFAST) can identify
pneumothorax before CXR
•  Best resolution of pleural interface with high-
resolution probe and small footprint but most
practical using same probe as FAST
•  Identify contiguity of visceral and parietal pleura
using simple US signs
–  Normal = lung sliding (B), seashore sign (M mode)
–  Abnormal = loss of lung sliding (B), stratosphere (M),
lung point (B & M)



•  “Air rises, water descends”
– Dependent disorders: effusion, consolidation
– Nondependent disorders: pneumothorax,
interstitial process



Normal Appearance:
Evaluate for Pneumothorax
•  Sagittal view at mid-
clavicular line “bat-sign”
–  Lung sliding?
–  A-line sign?
–  Lung point?



•  Normal lung sliding
–  Twinkling at level of pleural
line in real time
–  Sliding of visceral against
parietal pleura
–  Seashore sign on M mode
–  Avoid using filters that reduce
noise
Bright pleural line that moves on realtime scanning
seashore
Seashore sign on M mode



Pneumothorax:
Loss of Lung Sliding
•  Sensitivity 80-100%
(lower in trauma)
•  Specificity 83-100%
•  Real-time US
•  M mode = Barcode or
stratosphere sign
•  “Lung point” most specific
sign (alternating areas of
barcode and seashore
signs)
Barcode or stratosphere sign



Algorithm:
Looking for Pneumothorax on US
Lung
sliding
?
Yes
Pneumothorax
ruled out
No
B-
lines?
Yes
No
Lung
Point? No Use other
tools
Yes
Pneumothorax
Adapted from Lichtenstein D.



Pitfalls of US on Pneumothorax
•  “Loss of lung sliding” alone is not specific
for pneumothorax
– Pleural adhesion/thickening
– Atelectasis
– Lobec/pneumonectomy
– One-lung intubation
•  Look for “Lung Point” for specificity
•  Comparison with contralateral lung



FAST vs. CT
FAST CT
Aim for Detection of hemoperitoneum Detection of
hemoperitoneum, organ
injuries
Accuracy (for
hemoperitoneum)
88% Nearly 100%
Accuracy (for
organ injuries)
74% Nearly 100%
Missed rate 15% of hemoperitoneum. Up to
25% of liver/spleen, most renal/
pancreas/bowel
Benefits Fast, bedside, no patient prep
needed, no risk of IV contrast
issues
More accurate, guide
non-operative
management
ACR*
Recommendation
Done first and only if
hemodynamic unstable before
going to OR
Done if hemodynamic
stable
*The American College of Radiology



When to do CT
•  Blunt abdominal trauma
– Stable patients with positive FAST
– Stable patients with negative FAST but
suspicious for injuries (by clinical or labs)
•  Penetrating abdominal trauma
– Stable patients with injury to back & flank
– (stable patients with thoracoabdominal &
anterior stab wounds)



At Time of Receiving
Consultation
•  Must know mechanism of trauma
– Affecting use of contrast
•  Review portable CXR and pelvic XR
– Anything obvious been treated?
– Signs of aortic injury present? Does patient
also need chest CT?
– Pelvic fracture? If yes, is hematuria present?
Does patient need CT cystography?



Review portable trauma CXR…
Anything obvious been treated?
Inadvertent arterial line placement Left pneumothorax



Patient Preparation for CT
•  Hemodynamic – must be stable
•  NPO – should not wait
•  IV contrast – a must (if conditions allow)
•  Oral contrast – no need for routine cases
•  Rectal contrast – no need for routine cases
•  Renal function test – risk/benefit ratio
•  Pregnancy test - yes



CT Technique
•  Do whole abdomen!
•  No plain scan
•  Phases of scanning
–  With pelvic fractures: late arterial and portovenous
whole abdomen
–  Without pelvic fractures: Late arterial upper and
portovenous whole abdomen
–  + delays at site of injuries
•  If suspicion of TL spine fx, do small FOV axials
and coronal/sagittal reformations



CT Technique
•  Helical mode. Thinnest collimation possible and
reformatted to 2-2.5 mm for viewing
•  120 kV
•  Auto MA based on patient size
•  Lower dose for non-standard phases (i.e., late
arterial, delayed)
•  Must have coronal and sagittal reformations



Specific Questions
•  R/O bowel injuries
–  Oral, IV, rectal contrast
•  Penetrating trauma
–  Oral, IV, rectal contrast
•  R/O bladder injuries (gross hematuria + pelvic
fractures = a must do)
–  CT cystography using 300-400 cc of 2% contrast
instilled through a bladder catheter and image the
pelvis



Concerns of CT
•  Radiation dose can be reduced by
–  Routine use of automatic tube-current modulation
–  Reduce Z-axis (no plain scan or unnecessary delayed
scan)
–  Use of Adaptive Statistical Iterative Reconstruction
•  Maximize cost/benefit ratio
–  Use of clinical prediction rule, expert recommendation



Important/Urgent Must-Knows
•  Free fluid
– Differentiation of blood from other fluid
– Differentiation of intra- and extraperitoneal
blood
•  Free air
•  Active extravasation / vascular injuries
•  Hypoperfusion complex



Free Fluid
•  Common findings, seen in 75% of patients
with intra-abdominal injuries
•  Determine
– Where? (intra- or extraperitoneal)
– Type? (blood, urine, bowel content, bile,
ascites)
– Volume? (minor, moderate, major)



Free Fluid: Where?
•  Intraperitoneal fluid: Perisplenic, perihepatic,
Morison pouch, paracolic gutters, inframesocolic space,
lesser sac, between mesenteric leaves
•  Extraperitoneal fluid: pararenal, perirenal,
perivesical, pericholecystic spaces
•  Two confusing areas
– Morison pouch vs. perihepatic
– Pelvis vs. anterior prevesical space



Free Fluid: Where?
Intraperitoneal Blood Extraperitoneal Blood
Wraps around liver tip No
Location of primary organ injury in the peritoneum No
Cul-de-sac, mesenteric root Perivesical, anterior paravesical



Free Fluid: Type?
•  Always measure HU
•  Fluid does not
enhance! Changes in
attenuation from pre
to post contrast may
be seen but should be
minimal (<5-10 HU)
Type HU
Blood (acute) 30-45
Blood (clot) 50-60
Contrast (IV, oral, rectal) 100+
Clear fluid (urine, ascites,
bile)
<15



Free Fluid: Type
urine
Low-density free fluid in blunt trauma patient proven to be
urine leakage from intraperitoneal bladder on CT cystography



Sentinel Clot Sign
•  Blood accumulates adjacent
to site of bleeding
•  Indirect sign of injury to an
adjacent organ even if the
lesion could not be
identified
•  Orwig D and Federle MP*
–  Sentinel clot seen in
84% of visceral injuries
–  Sentinel clot only clue to
bleeding source in 14%
•  The rest, CT showed
injury itself (86%)
Orwig D and Federle MP. Am J Roentgenol 1989;153:747
Denser fluid



Free Fluid: Volume
•  You can estimate volume
of blood but this is less
important than
hemodynamic status
•  Each compartment:
Morison, perihepatic and
perisplenic, paracolic
gutters, pelvis
Amount
(cc)
#
compartment
s with fluid
Minor 100-200 1
Moderate 200-500 2
Large >500 > 2
Becker CD et al. Eur Radiol 1998;8:553.
Intraperitoneal Fluid Quantity



Free Fluid: Volume
•  Difficult to quantify
volume in
retroperitoneal bleed
Amount CT Character
Minor Fascial thickening
Moderate Confined to retroperitneal
space adjacent to its
origin (ie, perirenal,
anterior/posterior
pararenal)
Large Multiple communicating
retroperitoneal spaces
Retroperitoneal Hemorrhage Quantity



Active
Extravasation
•  Jet or focal area of
hyperattenuation (within 10 HU
of adjacent major vessel
source) within a hematoma on
initial images that fades into an
enlarged, enhanced hematoma
on delayed images
•  Indicates significant bleeding
•  Must be quickly communicated
to the clinician (surgical or
endovascular Rx may be
necessary)
Delayed



Pseudoaneurysm / AVF
•  Contained by connective tissue or vessel wall (ie, adventitia).
•  Adjacent to a vessel
•  Does not enlarge. Same size in all phases
•  CECT not reliable to differentiate the two
•  >70% of pseudoaneurysms progress to rupture but natural history of AVF is
uncertain
Pseudoaneurysm



Active Extravasation vs.
Pseudoaneurysm
Characters Active Extravasation Pseudoaneurysm
Edges Ill-defined Defined
Shape Commonly a jet (linear or
layering); may be diffuse
or focal
Often round or oval; possible
neck adjoining artery
Delayed
appearance
Increased attenuation or
size; possible layering
Less apparent; in isolation,
no change in size, similar
attenuation with vessels
Management Urgent embolization or
surgery if significant injury
present*
Urgent or ambulatory
embolization or surgery if
significant injury present*
*Not all injuries must be treated. Small pseudoaneurysms or those amenable to Rx by direct pressure do not



Hypoperfusion Complex
•  Flat IVC, small aorta
•  Enhanced: adrenals, kidneys, GB
mucosa, bowel mucosa
•  Hypoenhanced: liver, spleen,
pancreas, peripancreatic edema
Flat IVC, small aorta, hyperenhanced kidneys, hyperenhanced GI mucosa, and
peripancreatic edema caused by hypoperfusion state from left pelvic ring injury
Flat IVC
HyperenhancedGImucosa



Specific Organ Injuries
•  Solid intraperitoneal organs
•  Retroperitoneal organs
•  Hollow organs



Liver and Gallbladder
•  Common
•  Can be part of RUQ/midline “package injuries”
–  Shearing right lobe adjacent to hepatic veins
–  Compression left lobe
•  Vast majority managed nonoperatively
–  Surgery if severe injuries with active bleeding and/
or complete destruction of entire hepatic lobe
•  Right lobe (75%) > left lobe



•  Periportal tracking common, prob due to..
–  Lymphedema following systemic volume overload,
tension ptx, tamponade or
–  Hematoma obstructing hepatic venous outflow



•  Laceration involving hepatic veins (esp. if large >
10 cm focal hypoperfusion) associated with
injuries to retrohepatic IVC
laceration
Extraperitoneal blood



•  Liver laceration involving hilum
–  Repeated CT or US, cholescintigraphy or direct
cholangiography to detect possible biliary
complications
laceration



AAST Organ Injury Scale
Trauma.org



Splenic Injury
•  Most frequently affected organ in blunt trauma (?)
•  Contusion, parenchymal laceration, subcapsular
hematoma, perisplenic hematoma, fragmentation
of parenchyma and disruption of hilar vessels
•  Left lower rib fractures frequently associated
•  Perfusion defects due to segmental
devascularization from vascular pedicle injury can
be difficult to distinguish from contusions or local
reactive hypoperfusion in hypotensive patient



•  Contusion = hypodense area within normally
perfused splenic parenchyma



•  Laceration = linear perfusion defect



•  Subcapsular hematoma = lenticular shape with
compression of adjacent splenic paenchyma
–  Difficult to confidently see splenic capsule
–  Sometimes difficult to distinguish btw subcapsular and
perisplenic hematoma
Image from Radiology.cornfield.org



Nonoperative Management of
Splenic Injury
•  Now accepted practice: Success rate 95% in
children, 70% in adults
•  Well-recognized complication = delayed splenic
rupture
–  No reliable CT finding to predict risk of delayed
splenic rupture
–  Even a normal CT cannot exclude possibility of
delayed splenic rupture



Pancreas
•  <2% of blunt abdominal trauma
•  Up to 90% multiple organ injuries
•  Contusion, superficial or partial laceration,
complete transection or disruption
•  Can be difficult to diagnose clinically
– Delayed complications: recurrent pancreatitis,
fistula, abscess, hemorrhage
– Risk of abscess/fistula high (25-50%) if duct
disruption (vs. 10% if duct not disrupted)



Pancreas
•  Predict the presence or absence of ductal
disruption by depth of laceration and
location
– Grade A, pancreatitis or superficial laceration
(<50% pancreatic thickness)
– Grade B, deep laceration (>50% thickness) at
tail
– Grade C, deep laceration at head



•  Direct CT signs: Pancreatic enlargement, focal linear non-
enhancement, comminution, heterogeneous enhancement (subtle
initially)
•  Indirect CT signs: Peripancreatic fat stranding, fluid collections, fluid
separating splenic vein from parenchyma, hemorrhage, and
thickening of left anterior pararenal fascia
Focal linear non-enhancement
Focal linear non-enhancement



Bowel and Mesentery
•  3-7% of blunt abdominal trauma
•  Jejunum and ileum (near point of fixation—IC
valve and ligament of Treitz) most common
•  Colon: transverse, sigmoid and cecum
•  Stomach-rare
•  Duodenal injury: 2nd/3rd part in close proximity
to spine
•  Overall CT sensitivity/specificity 85-95%



•  Direct CT signs: 1) Discontinuity of wall, spillage of contrast or
luminal contents into peritoneal or retroperitoneal. 2) Extraluminal air
(definite for blunt trauma but not for penetrating trauma)
•  Indirect CT signs: 1) Focal bowel wall thickening, streaky
mesenteric fat, unexplained free fluid between mesenteric loops. 2)
Generalized bowel wall thickening nonspecific
Colonic contrast leakage
Perforation site at sigmoid colon
Bullet



•  Duodenal perforation vs. hematoma
–  Perforation  immediate surgery
–  Hematoma  conservative
•  Helpful if you can give oral contrast immediately before
scanning to see leakage
Perforation site
Circumferential wall hematoma



•  Mesenteric injury
–  Extravasation of contrast (active bleeding)
–  Intramesenteric fluid collections, hemoperitoneum,
thickening bowel loops in bowel ischemia
Initial scan
Delayed scan with
progressive increase of
extravasation



Adrenal Glands
•  2% of blunt trauma cases undergone CT
•  Usually unilateral, right sided and a/w
ipsilateral intraabominal and thorax injuries
•  Majority not clinically significant
•  Spontaneous resolution in 2 months
•  Specific Rx may be needed if: large
hematoma compressing IVC, bilateral
hematomas result in adrenal insufficiency



•  Round or ovoid, stranding of perirenal/periadrenal fat
•  Active bleeding due to injuries to suprarenal arteries
•  F/U CT in 2-3 months to ensure resolution if unable to differentiate from
pre-existing adrenal mass on trauma CT
Active contrast extravasation in adrenal hematoma
PortovenousArterial



Kidney and Ureter
•  Kidney injury = most common RP injury
•  Contusion, laceration, subcapsular hematoma,
shattered kidney, renal artery occlusion
•  Major renal hemorrhage with minor trauma
should raise suspicion of underlying pathology
(hydronephrosis, cyst, horseshoe kidney, AML,
RCC)
•  Macroscopic hematuria + stable  urethral
injury excluded then  CT



•  Renal contusion: focal zones of decreased
enhancement, striated nephrogram because of
temporarily impaired tubular excretion
Kawashima A, et al. Radiographics 2001



•  Laceration: linear or wedge-shaped hypodense area
–  Fracture = involving medial and lateral surface of kidney through hilum
–  Shattered kidney = laceration crossing kidney resulting in multiple fragments
Initial Delayed
Laceration
Active extravasation
hematoma
hematoma



•  Deep laceration results in
urine extravasation
•  Delayed scan for
confirmation
Initial Delayed
Excreted contrast in left ureter
Urinoma
Urinoma



•  Occlusion of main renal artery (subintimal tear with
subsequent thrombosis) or arterial avulsion
•  Cortical enhancement due to patent capsular arteries
originating proximal to occlusion should always raise
suspicion of injury to main renal artery
No enhancement



Urinary Bladder
•  Most pelvic visceral injuries = bladder and
urethra
•  Gynecologic injuries rare after blunt trauma
•  Urinary bladder 8% of patients with pelvic fx
•  Indicators of bladder injury
–  Macroscopic hematuria
–  Pubic rami fractures
–  Hemorrhagic shock upon admission



•  Extraperitoneal rupture
–  Direct perforation by bony fragment, rupture of pubovesical
ligament near bladder neck after symphysis injury or contusion
of distended UB
–  Often involves anterior bladder wall near neck
–  Conservative Rx
Bladder contrast in anterior perivesical space



•  Intraperitoneal rupture
–  More frequently caused by direct perforation of bone fragment (>
rupture of distended bladder)
–  Plugged by omentum or bowel loops making it difficult to detect
–  Surgical Rx
Perforation site
Low-density free fluid



CT Cystography
•  Antegrade bladder filling by excretion of IV
contrast is NOT enough to exclude bladder
injuries
•  Absolute indication: pelvic fracture + gross
hematuria
•  Technique: 300-500 cc of diluted (2%) contrast
instilled through a bladder catheter using gravity
drip, scan pelvis, drain bladder



AAST Organ Injury Scaling
Trauma.org



Conclusion
•  Trauma to abdomen “torso” often in setting of
multisystem injury
•  Choice of imaging depends on hemodynamics
and imaging availability
•  CT is the cornerstone in evaluation of stable
patients (impacting management and reduced
mortality)
•  Tendency toward non-operative management
makes use of CT for monitoring



Conclusion
•  Must know: free fluid, active extravasation,
hypoperfusion complex
•  IV contrast needed to assess solid visceral
organ and vascular injuries
•  Oral and rectal contrast may be needed in
penetrating abdominal trauma
•  Antegrade filling of bladder is not enough to
image of suspected bladder injury.

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