Week 5

Question 1

What is the significance of an ileus?

Answer 1

May be a harbinger of oncoming obstruction, or it may resolve
-Retains potential to evolve into obstruction in the next 1-2 days
-CT definitive study

Question 2

What happens in a blockage?

Answer 2

1) Peristalsis continues before and after obstruction in an attempt to clear the blockage
Proximal loop(s) of bowel become enlarged
Distal loop(s) become decompressed
2) The part that can get the biggest will get the biggest
-In LBO, this is the cecum
-In SBO, this will be the section of bowel just proximal to the obstruction

Question 3

Localized Functional ileus:
1) What is it?
2) Where is it usually found?
3) What points to underlying pathology? Explain

Answer 3

1) Focal irritation of bowel leading to aperistalsis  proximal dilatation
2) Usually in small bowel (think pancreatitis or appendicitis)
3) “Sentinel loops”  they point to underlying pathology
This adjacent pathology is sometimes discoverable on CT

Question 4

Localized Functional Ileus: What are the key imaging features? Explain

Answer 4

1) 1 or 2 persistently dilated loops of bowel
Meaning they are persistently dilated across different views or on several studies across time
Dilated = more than 2.5 cm (a quarter)
2) Air fluid levels present in the dilated loops
3) Usually small bowel . . . Usually
A notable exception would be LB ileus secondary to appendicitis
Air in rectum or sigmoid

Question 5

Generalized Functional Ileus: What are the key imaging features? Explain

Answer 5

1) Entire bowel air-containing and dilated
2) Air-fluid levels usually present
3) Still gas in rectum or sigmoid
4) NO TRANSITION POINT ON CT
-Because the whole thing is distended
5) Lots of air

Question 6

What aer some DDxs for generalized functional ileus?

Answer 6

Recent surgery
Recent surgery
Recent surgery
Electrolyte imbalance
hypokalemia
Not ileus at all
Aerophagia

Question 7

SBO
1) What is it?
2) What does it cause?
3) Is there dilation?

Answer 7

1) A lesion in the abdomen causes a complete blockage
2) Bowel continues to undergo peristalsis both proximally and distally
Air continues to be swallowed, and fluid is secreted into bowel from GI tract  air/fluid levels
3) Bowel dilates significantly proximally, and bowel is emptied distally

Question 8

What does SBO look like on imaging?

Answer 8

Dilated loops with air fluid levels
Step ladder appearance

Question 9

Describe the key imaging features of SBO in detail

Answer 9

Multiple dilated loops: Loops may stack up on one another, causing a step-ladder appearance

Thinking logically, the more proximal the obstruction, the fewer dilated loops there will be
Because obstruction is a complete blockage, usually not air in rectum/sigmoid
There should be a noticeable difference between big, dilated small bowel and small, compressed large bowel
The key feature on imaging is transition point which is only discoverable on CT

Question 10

LBO:
1) What is it?
2) Is there dilation? Explain

Answer 10

1) A lesion either within or outside of the colon causes obstruction
2) Dilation occurs proximally
Usually NOT in the SBO though if the ileocecal valve works
ICV prevents dilation from passing backwards into the small bowel

Question 11

LBO:
1) What occurs distally?
2) Do you see air fluid levels in LBO?

Answer 11

1) Compression distally
2) Large bowel normally functions to reabsorb water, which is why you rarely see air fluid levels here

Question 12

Name and describe a special case of LBO

Answer 12

1) Volvulus: Caused by large bowel twisting on itself
2) Can cause VERY large dilation 2ith classic appearance
-Coffee-bean shape

Question 13

How do you distinguish partial SBO from localized ileus?

Answer 13

1) A partial SBO lets a little air get through
So, you actually can see some gas in the rectum/sigmoid
This makes things very confusing
2) You will get a CT scan if you have serious clinical concern for obstruction
-Pt with intense abdominal pain +/- vomiting, reduced bowel sounds, commensurate history

Question 14

Ogilvie Syndrome: What does it cause?

Answer 14

Loss of peristalsis
Massive and diffuse dilation

Question 15

What is a sign of free air other than near diaphragm?

Answer 15

Both Sides of bowel wall are visible

Question 16

Visualization of the Falciform Ligament:
Is this normal? Explain

Answer 16

Normally this structure is too closely surrounded by tissue of similar density
Not so when the abdomen has large amount of free air (FA)

Question 17

List the signs of retroperitoneal air

Answer 17

Streaky, linear appearance (outline structures)
Mottled, blotchy appearance (fixed, especially @ beans)
Does not move freely or change with position
May outline extraperitoneal structures
Psoas muscles
Kidneys
Aorta and vena cava

Question 18

What does Pneumatosis look like?

Answer 18

Linear black line (may appear bubbly)
Traces the contour of the bowel lumen

Question 19

How does Pneumatosis appear when seen en face?

Answer 19

It a appears mottled
(much harder to pick up, if unsure
Get CT)

Question 20

Air in biliary system: Is this normal? Explain

Answer 20

1) Gas here can be normal; Prior surgery can cause this
2) Gas-forming cholangitis