1. Educational Objectives
- Identify common pitfalls in interpretation of blunt abdominal trauma CT studies
- Optimize CT acquisition techniques to reduce likelihood of missing potentially significant injuries
- Develop a search pattern that includes organs and areas where important lesions are commonly missed
2. Sources of Error/Pitfalls
- Improper MDCT technique
- Degradation by artifacts
- Patient-related factors: body habitus, low cardiac output, overhydration
- Anatomic variants, pre-existent conditions
- Potentially physiologic (vs. significant) findings
- Subtle or difficult-to-perceive injuries (true misses)
3. MDCT Technique
- NO oral contrast
- YES intravenous contrast at fast rate, saline chaser
- Radiation modulation techniques to lower dose, BUT diagnostic quality should not be compromised
- Routine orthogonal plane reformations
- Number of phases: 1, 2 or 3?
- CT cystography: full bladder, can be combined with delayed series
4. CT Phases in Abdomino-Pelvic Trauma
- PVP of upper abdomen (65 to 70 sec): detection of solid organ injury (peak parenchymal enhancement)
- Second (third?) phases:
- “Second look”: confirm questionable finding, characterize bleeds: active vs.contained vascular injury
- Delayed (5 to 7 minutes):
- Determine integrity of renal collecting system and ureters
- Arterial (22 to 30 sec):
- Optimal evaluation of vascular structures
- Low radiation dose for delayed andarterial phases
5. Multi-phasic imaging for Characterization of Bleeds
- Active extravasation:
- Not contained
- Morphology and size change over time
- Attenuation likely > aorta on delayed images
- Pseudoaneurysm:
- Contained
- No change in morphology on delayed images
- Attenuation similar to aorta
6. Recommendation
- ALWAYS:PVP Abdomen/Pelvis
- Severe trauma ORinjury seen in PVP: at least one more phase (often two more):
- Arterial phase of A/P: vessels, displaced pelvic
- Delayed phase A/P: selective, findings on PVP
- CT cystography: pelvic fracture/hematoma, gross hematuria
- Radiation?:
- NOT main concern in initialCT for major trauma
- Arterial and delayed series: low radiation technique
7. Problematic Anatomic Variants
- Splenic clefts
- very common finding
- often source of confusion
- clefts: well defined, linear, medial
- true laceration: irregular, surrounded by blood
- may be indistinguishable
8. Easily (but important!) Missed Injuries
Lawson CM et al. Missed injuries in the era of the trauma scan. J Trauma 2011: 26,000+ trauma scans, > 8 years
- Bowel and Mesentery
- Pancreas
- Diaphragm
- Major vessels: arteries, veins
9. Bowel Trauma
- Challenging diagnosis: most commonly missed significant injury!
- 1-2% abdominal trauma patients
- Leading cause of failed conservative therapy and delayed laparotomy
- Delay in diagnosis (8 hs!!) is important cause of morbidity and mortality in blunt trauma
10. Mortality in Hollow Viscus Trauma
- Independent risk factors for mortality:
- – Age (odds ratio [OR] = 1.04, p = 0.005)
- Presence of significant extra-abdominal injury (OR = 3.4, p = 043)
- Delay of more than 5 hours between admission and laparotomy(OR = 2, p = 0.0499)
- 86% of deaths in patients who had a delay of >5 hours were because of abdominal-re- lated
11. CT Findings –Bowel Injury
- Bowel wall discontinuity
- Extraluminalair
- Intramural hematoma/Intraluminalbleeding
- Bowel wall thickening
- Bowel wall enhancement
- Pneumatosis
- Free intra-or retroperitoneal fluid
12. Bowel Wall Thickening as Sign of Injury
- Unequivocal, localized thickening: contusion, hematoma, ischemia (i.e., “surgical” lesion)
- Associated high attenuation free fluid
- Triangular accumulations of fluid between leaves of mesentery
- Diffuse thickening: hypoperfusion complex (“shock bowel”)
- Additional associated findings
13. Free Fluid in Trauma
- Free fluid in peritoneal cavity
- Often with solid organ injury
- ? hollow viscus injury
- Isolated free pelvic fluid in females
- Physiologic
- Isolated free fluid males
- Raises suspicion of occult injury
14. Isolated Free Fluid in Males:Physiologic or Significant?
- Drasin E et al(AJR ’08): 669 consecutive males
- 8% isolated finding
- Mean attenuation= 10.6 HU
- 0 proven bowel injury
- Yu J et al (Radiology ‘10): 1000males
- 8% isolated fluid, all below S3 vertebral body
- Mean attenuation= 8.1 HU
- 0 proven bowel injury
- Likely cause: IV fluids for resuscitation
15. Management Implications
- Isolated free fluid in males after blunt trauma
- Carefully scrutinize for direct signs of bowel or mesenteric injury
- Recommendation:
- Admit
- Observe for at least 24 hs
- Optional: Repeat CT with oral contrast, 12 hs later (earlier if abdominal pain develops)
- No mandatory exploration
16. Extraluminal Air
- Intra-or retroperitoneal
- Appropriate window settings (lung or bone)
- Sensitivity: 50-75%, may appear over time!
- Pitfalls (FP, ):
- DPL
- Barotrauma and mechanical ventilation
- Bladder rupture
- “Pseudopneumoperitoneum” -Extraperitoneal
17. Pseudopneumoperitoneum
- Air trappedbetweenabdominal walland peritoneum
- Foundwithextraperitonealrectal injuries, ribfractures, pneumothoraxorpneumomediasti- num
- Maycoexistwithpneumoperitoneum!
- Troubleshooting:
- true pneumoperitoneum: + collectionsof gas deeperin abdomen oradjacenttoruptu- redviscus
- ifin doubt: delayedimagesordecubitusseries
18. Pancreatic Trauma
- Uncommon injury: ~ 2% patients admitted with blunt trauma
- …but important!
- 20% mortality: majority occur in initial 48 hours
- Early deaths: acute hemorrhage
- Delayed complications tardias: fistula, abscess, hemorrhage, sepsis
19. Imaging the Pancreatic Duct
- MDCT may demonstrate duct directly
- Injury also predicted by depth of laceration
- Pancreatography: MRCP, ERCP
- Advantages of MRCP:
- Non-invasive, no radiation!
- Used mostly for surveillance and follow-up
- Advantages of ERCP:
- Complete visualization of pancreatic duct
- Ability to diagnose injury and treatment in some patients: stent placement
20. MR in Pancreatic Trauma
- Why?
- Confirm / clarify questionable CT findings
- Evaluation of pancreatic duct: non-invasive alternative to ERP
- Follow-up of panc lacs: young patients/children (radiation)
- Monitoring of fluid collections / duct stenosis
21. Pancreas: Problematic Variants
- Pancreatic clefts
- linear hypoattenuating defects oriented perpendicular to long axis of the gland
- usually contain fat
- Lobulations, fatty replacement
- Anatomic variants common, usually in the head, may mimic laceration
- Fatty replacement: elderly, obese, diabetics
- Solution: delayed images (5 to 7 min), repeat CT (24 to 48 hours), MR as problem solver
22. Diaphragmatic injuries
- Sensitivity of CT traditionally considered low
- Right hemidiaphragm especially problematic
- MDCT:
- Spatial resolution: subtle findings
- Multi-planar reformations
- Multiple signs described
- Direct discontinuity and abnormal location of abdominal viscera
23. Major Vascular Injuries
- Rare, highly lethal
- Rapid deceleration, direct crush injury, flex-ext
- Findings: active extravasation, pseudoaneurysms, dissections, intimal flaps, thrombosis
24. Summary: Avoiding Traps
- Multiple phases: rational use, be aware of radiation dose but do not cut corners!
- Routine orthogonal MPR’s
- Search specifically for easily missed significant injuries: bowel, pancreas, diaphragm, vessels
- ? Significant injury on initial CT: admit, observe, repeat CT if necessary (bowel: short interval)