- Collar sign: narrow waist of herniated hollow organs as they herniate through diaphragmatic defect
- Disrupted diaphragm sign
- Dependent viscus sign: posterior wall of stomach lies in contact with posterior wall of the chest (which it normally doesn't)
Use of Triple contrast for colon injuries:
- with multidetector CT, may not need po/pr contrast to detect a colonic injury
- there are usually secondary signs such as a hematoma or air bubbles
- instilling rectal contrast has an inherent false negative rate as well
- pt may still need an exploration if suspicion high enough.
- ?if rectal bleed and penetrating stab or pelvic fracture just explore abdomen, rectal contrast perhaps useful if mechanism present but no clinical suspicion of injury and it may prevent an OR
Houndsfield Units:
- Fresh blood: 20-30 HFU (decreased intensity if old blood, or mixed with ascites, urine)
- Blood with IV contrast: 30-40 HFU
- Fat: <-10 HFU
- Water: 0-10 HFU
- Urine: 0-10 HFU
- Non-contrast (fatty) liver: 10-15 HFU
- Fatty liver contrast phase: 35-40 HFU
- Normal contrast phase liver: 70-80 HFU
- Bone: 400-500 HFU
- Metal: 1000 HFU
- Enhanced aorta: 190
- po contrast: 50-200 (depends on dilution)
Oral contrast can be negative or positive: use of a positive (ie; enhances) contrast agent prevents you from visualizing the bowel wall
- if you want to visualize the bowel wall then water contrast (negative) better
Radiation Exposure:
CT/Abdo/Pelvis:
- old scanners 10-15 mSi
- newer generation of scanners 3-4 mSi
10mSi of radiation carries a 1:2000 lifetime risk of cancer
- consider that everyone has a 1:5 lifetime of risk of caner without any exposure risk
- Therefore if CT is clinically indicated then theoretic risk of inducing cancer should not be a barrier
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