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: 418-27 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 US @ 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. REFERNCES: 1. Beal SL. Fatal hepatic hemorrhage: an unresolved problem in the management of complex liver injuries. J Trauma 1990;30: 163-9. 2. Significance of minimal or no intraperitoneal fluid visible on CT scan associated with blunt liver and splenic injuries: a multicenter analysis. Ochsner MG, Knudson MM, Pachter HL et al. J Trauma. 2000 Sep;49(3):505-10. 3. Shuman WP. CT of blunt abdominal trauma in adults. Radiology1997 Nov;205(2):297-306. 4. Branney SW, Wolfe RE, Moore EE et al. Quantitative sensitivity of ultrasound in detecting free intraperitoneal fluid. J Trauma 1995 Aug;39(2):375-80. 5. Ma OJ, Mateer JR, Oqata M et al. Prospective analysis of a rapid trauma ultrasound examination performed by emergency physicians. J Trauma 1995 Jun;38(6):879-85. 6. Lingawi SS, Buckley AR. Focused abdominal US in patients with trauma. Radiology 2000 Nov;217(2):426-9. 7.McGahan JP,Richards JR. Blunt abdominal trauma: the role of emergent sonography and a review of the literature. AJR1999 Apr;172(4):897-903. 8. Nordenholz KE , Rubin MA, Gularte GG et al. Ultrasound in the evaluation and management of blunt abdominal trauma. Ann Emerg Med 1997 Mar;29(3):357-66. 9. Catre MG Can J Surgery 1995:38 10. Roberts JL Sem US, CT and MRI 1996:17 11. Brasel KJ, Olson CJ, Stafford RE, Johnson TJ. J Trauma 1998 May;44(5):889-92. 12. Poletti PA, Mirvis SE, Shanmuganathan k et al.CT criteria for management of blunt liver trauma: correlation with angiographic and surgical findings. Radiology 2000; 216: 418-27 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