On Alert! Flashcards
Clue to differentiate portal venous air from pneumobilia
Air extends to the peripheral margins of liver if in portal vein
Suspicion for mediastinal/aortic injury chest X-ray
- rightward displacement of ETT and NGT
- indistinct/irregular cardiac contour
- downward displacement of Lt main bronchus
- apical capping
- fracture of 1st and 2nd ribs (high energy impact)
- *widened mediastinum (non-specific)
Mechanism of injury that raises suspicion for aortic injury
Aorta firmly fixed at its root to ligamentum arteriosum and diaphragm
Rapid deceleration causes shear injury commonly at ligamentum a.
Mediastinum:
What does a fat plane between aorta and hemorrhage suggest?
Hemorrhage is not secondary to aortic injury
What can mimic an intimal flap when looking for aortic injury?
Pulsation artifact!
Clues to traumatic aortic pseudo aneurysm
- crescent sign
- intimal flap
- widened lumen (ovoid)
Significance of aortic wall hematomas
Can progress to dissection and pseudoanuerysm
Aortic dissection classification and treatments
Stanford classification:
Type A: any part of the aorta proximal to the origin of the left subclavian artery (A affects ascending aorta)
EMERGENCY! Surgical intervention
Type B: distal to left subclavian artery origin
Medical mx: BP control
trauma
What does active bleed indicate?
Risk of end organ ischemia/necrosis
Impending hemodynamic collapse
*on delayed images, the extravasated contrast will diffuse into hematoma
Acute hemorrhage density (HU)?
About 40 HU
As blood clots it becomes more hyper dense
Easy to miss abdominal injuries?
- retroperitoneal duodenum
- mesentery
- pancreas
- bowel
- small spine injuries
Abdominal trauma:
Surgeons need to know …
- solid organ injuries
- active bleed
- secondary signs > mesenteric stranding, hemoperitoneum, extraluminal air
Solid organ lacerations and contusions appear as…
Linear and amorphous areas of hypoattenuation
Pancreas inflammation in trauma setting
Indicates pancreas contusion or pancreatitis
Common in children!
Also seen in adults
Secondary signs of pancreatic trauma
- peripancreatic fat stranding
- fluid between pancreas and splenic vein *sensitive
- thickening of the anterior pararenal (Gerota) fascia
- peripancreatic retroperitoneal fluid
- intraperitoneal fluid, especially in lesser sac
- adjacent injuries e.g. spleen, liver, biliary and duodenum
Renal injuries
- infarcts (linear geographic)
- contusion (amorphous)
What does active extravasation look like?
Extravascular contrast as bright as in vessels surrounded by hematoma (on arterial phase), which diffuses into hematoma on delayed imaging
Active extravasation vs pseudoaneurysm
Active extravasation- associated with hematoma, irregular contour, and dissipates on delayed images
Pseudoaneurysm-
- smoothly marginated extraluminal contrast collection
- follows vessel enhancement on all phases
- usually no surrounding hematoma
Urinary tract injuries, CT contrast phases
Injuries usually not seen on arterial phase (contrast has not filtered through kidney)
Delayed phase (3-5mins)- contrast in urine
Space of Retzius
Extraperitoneal
“Virtual space”
Peritoneal reflection between peritoneal cavity, bladder and anterior abdominal wall
Usually collapsed-unless filled with fluid/hemorrhage/contrast
Intra vs extra peritoneal bladder rupture mx
Intra - surgical
Extra- conservative
Mesenteric tears
Ill defined area of fat stranding
Wedge shaped fluid collections
Shear injuries
Can be subtle
*loops of bowel downstream at risk of ischemia and infarct
Trauma
Bowel ischemia/infarct
- underperfusion (under/non-enhancing) of focal segment of bowel
- surrounding stranding
- wedge shaped fluid collections in mesentery interdigitate between bowel loops
- focal bowel wall thickening
- pneumatosis
- portal venous air
IVC injury findings:
- fluid tracking along IVC
- contour abnormality
- signs of contained rupture (pseudoaneurysm or active extravasation)
*collapsed IVC > seen in dehydration/volume depletion, could also be a sign of impending circulatory collapse
Types of aneurysms
Fusiform and saccular
CT Stroke evolution
Hyper acute (<24hrs): hyper dense vessel, subtle loss of grey-white differentiation, subtle hypodensity
Acute (24hrs-1wk): hypoattenuation and swelling become more marked
Subacute (1wk-3wks): swelling starts to subside and small amounts of cortical petechial haemorrhages (don’t confuse with haemorrhagic transformation) result in elevation of the attenuation of the cortex. This is known as the CT fogging phenomenon.
*Imaging stroke at this time can be misleading as the affected cortex will appear near normal.
Chronic (>3wks): gliosis sets in eventually appearing as a region of low density with negative mass effect. Cortical mineralisation may be seen appearing hyperdense.
Types of brain atrophy CT
- diffuse/global
- limited to frontal lobes
- cerebellum
Types of brain edema CT
Cytotoxic: edema of grey-white matter» characteristic for stroke (also possible with encephalitis)
Vasogenic: edema of white matter»_space; characteristic of mass/hemorrhage
Stroke window vs Brain window
Stroke»_space; window width-40: level-40
Brain» 80:40
Brain:
Calcarine sulcus location
located on the medial surface of the occipital lobe, just adjacent to flax and tentorium»_space;divides the visual cortex into two
Brain CT
Ideal level to measure midline shift
At the level of the caudate heads
Brain
Common midline crossing tumors:
Crossing corpus callosum:
- Glioblastoma multiforme (irregular peripheral enhancement with central necrosis)
- Lymphoma
- MS
extra-axial:
Meningioma
Small Bowel Obstruction : how to assess CT?
- compare proximal vs distal loops (? Caliber difference)
- ? Transition point
- closed vs open loops
- complete vs partial
- air-fluid levels
- bowel wall»_space; thickened = ischemia, pneumatosis = necrosis
- ascites/ stranding
- free air in portal vein/ SMV
- pneumoperitoneum
- Causes ?? Hernia/ Intra-abdominal mass/ IBD/ Volvulus
What is Closed loop obstruction?
Loop of distended bowel that loops back on itself
>loop itself is distended
> bowel proximal to loop is distended
>distal bowel is decompressed
>”double beak sign” -tapering bowel loops at point of obstruction
> “whirl sign”-twisted mesentery
Causes:
- adhesion
- internal hernia
- volvulus
** in large bowel know as volvulus (cecal/sigmoid)
