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)


Detection of Pneumothorax

•  “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?


Detection of Pneumothorax

•  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

Hyperenhanced G

I mucosa


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



Trauma.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

Portovenous Arterial


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



Trauma.org



Trauma.org


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.

Date post:	07-May-2015
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Imaging of Abdominal Trauma

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