1. Blunt Hepatobiliary Trauma: Role of Low Dose MDCT in Diagnosis and Patient Management
Eftekhari A, Galea-Soler S, Yong-Hing CJ, Nicolaou S, Zwirewich CV, Hou DJ, Co SJ, Louis L
Vancouver General Hospital, Department of Radiology, University of British Columbia
INTRODUCTION
The liver is the second most commonly injured organ in blunt abdominal trauma (BAT). The right lobe is most commonly injured, however left lobe lacerations are associated with increased risk of duodenal and pancreatic injury. Hepatobiliary (HPB) injuries range from simple parenchymal contusions to extensive lacerations with devascularisation. Vascular injuries involving the hilar structures require immediate surgical management. Moreover, injuries to the retro-hepatic inferior vena cava have a reported mortality rate of 90 – 100% (1). Haemoperitoneum can be absent in 11% of cases (2). MDCT plays a crucial role in the management of blunt HPB trauma as non-operative management is possible in 50-82% of adults (3). Thus, reduction of dose is essential given the majority of BAT will undergo MDCT examination. In this illustration we will introduce our low dose MDCT protocol and the role of MDCT in triaging patients into operative vs. non-operative arms.
Table 1: AAST Liver Injury Scale
A) Grade III, >3cm laceration with high
attenuation focus (arrow) suspicious for pseudoaneurysm. B) US demonstrates a cystic lesion (arrow) with C) high velocity, turbulent flow on Doppler interrogation consistent with a pseudoaneurysm. D) Angiography demonstrates pooling of contrast indicating right segmental hepatic artery pseudoaneurysm (arrow) which (E) was successfully treated with coil embolisation (arrow). C B A D
Grade
I Hematoma: subcapsular, <10% surface area
Laceration: Capsular tear, <1 cm parenchymal depth
II Hematoma: subcapsular, 10-50% surface area; intraparenchymal. <10 cm
Laceration: 1-3 cm in parenchymal depth, <10 cm in length
III Hematoma: subcapsular, >50% surface area or expanding or ruptured
subcapsular hematoma with active bleeding; intraparenchymal, >10 cm or
expanding or ruptured
Laceration: >3 cm in parenchymal depth
IV Hematoma: ruptured intraparenchymal hematoma with active bleeding
Laceration: parenchymal disruption involving 25-75% of a hepatic lobe or one to
three Couinaud segments within a single lobe
V Laceration: parenchymal disruption involving >75% of a hepatic lobe or more
than three Couinaud segments within a single lobe
Vascular: juxtahepatic venous injuries (retrohepatic vena cava or central major
hepatic veins)
VI Vascular: hepatic avulsion
TABLE 2: NEW LOW DOSE MDCT PROTOCOL
Portovenous/ nephrographic
b) Delayed
Tube voltage (kV)
100
120
Reference mAs
250 70
Rotation Time (s)
0.5
Detector Configuration
64 x 0.6mm
Feed/Rotation
18mm/rot
Width/Spacing (mm)
5/2.5
Care Dose 4D On
TABLE 2: RADIATION DOSE
Previous Protocol
i) Portovenous
ii) Delayed
Total
CTDIvol (mGy)
15.1
13.9 -
DLP (mGy·cm)
821
700
1521
Effective Dose (mSv)
12.3
10.5
22.6
Low-Dose Protocol
6.4
347
1168
6.8(M) 9(F)
5.2
17.5
Adapted from: Radiology 2000; 216: A C
A young skier with Grade IV injury who was managed non-operatively. A) Day 3 post injury: Deep laceration extending to the hilar structures with a subcapsular haematoma. B) Day 4 post injury: Contrast extravasation on ERCP indicates a bile leak. C) Day 14 post injury: Doppler US shows flow in a cystic structure confirming a post-traumatic pseudoaneurysm (arrow). D) 8 weeks post injury: Successful coil embolization of pseudoaneurysm. B D
NEW LOW DOSE MDCT TECHNIQUE
Following IV injection of 120cc of 320mgI/ml non-ionic contrast media at 3cc/sec followed by a 50cc saline chaser at 4cc/sec, low dose portovenous imaging (ref
ROLE OF IMAGING
Management of BAT patient primarily depends on two parameters:
The patient’s haemodynamic status
The MDCT result
Haemodynamically unstable patients with a positive FAST go directly to the operating room.
Haemodynamically stable patients with a significant history of BAT are assessed primarily with MDCT.
mAs 200, 4D Care Dose On) from the diaphragm to pubic symphysis is performed at 70sec post-injection to assess for parenchymal / vascular injury. Low dose delayed images (ref mAs 70, 4D Care Dose on) are obtained from top of liver to pubic symphysis. In addition, in patients with an AP dimension of < 24cm (measured at level of L1), further 47% dose reduction is achieved by dropping from 120 to 100kV. As depicted in table 2, ImPACT CT Patient Dosimetry calculations for this new low dose portovenous scan yield an effective dose of 6.8 and 9 mSv for male and female patients, respectively.
MDCT FINDINGS OF BLUNT HEPATOBILIARY TRAUMA: Pictorial Review
IMAGING MODALITIES
Figure 1: BLUNT HEPATOBILIARY TRAUMA IMAGING ALGORITHM
Patient with 10 foot fall from the roof and resultant BAT: A) Periportal edema (arrow) and large-caliber IVC (arrow head) secondary to fluid resuscitation. B) Small contusion (intraparenchymal haematoma) in the right liver lobe (arrow) in keeping with AAST grade I injury. In another patient with BAT C) a laceration involving segment VII of the liver (arrow) is demonstrated in keeping with AAST grade II injury. A C B
FAST (Focused Abdominal Sonography in Trauma)
Accurate in detecting free intraperitoneal
fluid (81-98% sensitive, >96% specific(4-6).
DIAGNOSTIC US
Accurately localises the intra-abdominal
injury site in 23-44%; poor (14%)
Accuracy with respect to liver injuries (7).
DPL
Sensitivity of 97%, >98% specificity
For detection of haemoperitoneum (8).
Low false positive/false negative rates
of <1.5%.
May be “oversensitive” resulting in
nontherapeutic laparotomies.
Decreases specificity of subsequent US
or CT (9).
HIDA scan
Can be useful in confirming presence
of bile leak or presence of a biloma.
Hepatic laceration with active extravasation of contrast which is pooling inferiorly (arrow) consistent with a Grade IV injury.
MDCT
CT Evidence of
HPB injury
AV fistula
Pseudoaneurysm
Expanding subcapsular hematoma
Hemobilia
No adverse change
No CT evidence of pseudoaneurysm
active extravasation
or clinical deterioration
Monitor Hgb, BP, ABG
Bladder pressures Q12h x 72hrs
CT evidence of pseudoaneurysm
Angio or OR
Repeat low dose MDCT
+/- Doppler 72hrs
Angio or OR
Biliary peritonitis
No biliary peritonitis
CT evidence of bilioma
Percutaneous drain
ERCP and biliary stent
Stable Patients With Significant
Blunt Abdominal Trauma
Unstable patient
FAST +
FAST -
Detectable pulse
Non-operative management of a grade IV injury. A) Deep liver laceration with large low-attenuating collection suspicious for biloma (arrow). B) Contrast extravasation on ERCP from right and left bile duct injuries (arrows). D) Repeat ERCP after successful stenting. A B C
AAST Grade III injuries. Young patient with a fall while horse-riding. A,B) Lacerations in the right liver lobe extending through the capsule (arrow). C) A different patient with BAT and right lobar laceration
(arrow), no active extravasation demonstrated. Small subcapsular hematoma is also present. D) In the same patient, a sagittal US of the liver shows a hypoechoeic lesion (arrow), consistent with
laceration. A B D C
Abnormal gallbladder morphology (arrow) with surrounding high-attenuation fluid consistent with haemoperitoneum (arrowhead) – finding in keeping with with gallbladder perforation.
A) US images reveal a cystic lesion (arrow) within right lobe of liver in a patient with BAT. HIDA Scan. C & B) immediate images and D & E) Delayed images reveal concentration of radiopharmaceutical
within cystic lesion indicating a biloma.
Anterior
Right Lateral A B E C D
AAST grade IV injuries. Patients involved in MVC. A) Active vascular extravasation from an extensive right lobar laceration (arrow), haemoperitoneum (arrowhead), small spleen secondary to
hypovolemia. B) Bilobar hepatic lacerations (arrow), more extensive on the right side, with haemoperitoneum (arrowhead), small-caliber aorta secondary to hypovolaemia (black arrowhead). C) Complex
right hepatic lobar laceration (arrow), with strong suspicion of injury to the right hepatic venous pedicle, as well as an area of altered perfusion suspicious of devascularisation. D) Significant laceration
involving most of the right liver lobe (arrow), extending from the IVC (black arrowhead) to the liver capsule – high risk of vascular injury. The spleen is small secondary to hypovolaemia and
hemoperitoneum (arrowhead) is demonstrated. C A B D
MDCT
Sensitivity of 97.6%, specificity of
98-100% with respect to detection
of haemoperitoneum.
92-98% accuracy for solid organ injury
evaluation(10).
At least 77% of patients with free fluid
have a solid organ injury.
Isolated FF is seen in 3% of BAT (11).
patients with isolated trace amounts of
free fluid can be safely observed.
54% of cases with moderate-large
haemoperitoneum end up having a
laparotomy.
ERCP
Useful in identifying site of biliary leak
and instituting therapeutic intervention
(stenting).
LIVER INJURY GRADING SCALE
Clinical grading systems are devised to predict patient outcome (Table 1). Grade IV injuries have a higher likelihood of bleeding and delayed complications when compared with grade III injuries. In general, higher injury grades associated with likelihood of failing non-surgical management (5). However, incorporation of MDCT findings such as active arterial extravasation, pseudoaneurysm, hepatic vein involvement can be helpful in predicting invasive vs. conservative management.
CONCLUSION
Given the widespread usage of MDCT in assessing the hepatobiliary tree in blunt trauma injuries, a reduction in patient dose is essential. We have described our new low dose MDCT protocol, which can achieve up to 50% dose reduction while still assuring diagnostic image quality in helping guide patient treatment. We have also shared our institutional blunt hepatobiliary MDCT imaging algorithm which can help triage patients towards conservative or operative management.
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AAST injury Grade IV - pedestrian hit by vehicle at 45mph. A) Deep liver laceration (arrow) extending into the hilar vessels (arrowhead). B) Another example of a grade IV injury with a haematoma in the right lobe of the liver with a deep laceration (arrow) extending to the IVC (arrowhead). C) Vascular extravasation of contrast (vertical arrow)and CT evidence of hypovolemic shock as evidenced by small-calibre aorta (arrowhead), diffusely thickened small bowel loops (horizontal arrow) , small spleen and flattening of the IVC (black arrowhead). D) Patient with severe BAT - Laceration causing parenchymal disruption in >75% of the right lobe. A B C D