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Radiologic Pathologies 3461 > Mod 5-2 SBO > Flashcards

Mod 5-2 SBO Flashcards

1
Q

What is small bowell obstruction considered to be?

A

The most common disorder of the small intestine requiring surgical intervention to correct.

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2
Q

How does an obstruction occur?

A

From a mechanical process that blocks passage of contents within the bowel so that material cannot move beyond a given point.

*i.e. a lesion is present obstructing flow

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3
Q

List mechanical processes that are responsible for SBO and their frequency.

A
  • Adhesions 60-75% (SCAR TISSUE, an abnormal union of membranous surfaces due to inflammation or injury)
  • Tumors 20%
  • Hernias 10%
  • Inflammatory bowel disease 5%
  • Volvulus 3% (an obstruction caused by twisting of the stomach or intestine)
  • Miscellaneous 2%
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4
Q

What would an example of a non-mechanical obstruction be?

A

An ileus which is a lack of peristaltic activity and not a true obstructive process.

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5
Q

What are the three forms of a mechanica obstruction?

A
  • Simple obstruction
  • Closed loop obstruction
  • Strangulation
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6
Q

What is a simple obstruction?

A

When only the intestinal lumen is occluded

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7
Q

What is a closed loop obstruction?

A
  • When occlusion occus at 2 ends of a loop of bowel.
  • Contents can enter the proximal end but cannot pass distally or reflux proximally.
  • This can sometimes lead to a third kind of obstruction- strangulation.
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8
Q

What is strangulation?

A

When the blood supply is impaired resulting in necrosis of the bowel wall.

*Can be caused by closed loop obstruction

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9
Q

What is the number one cause of SBO in developing countries such as the U.S.?

A

Postoperative adhesions (60-75%)

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10
Q

List the surgeries closely associated with SBO and related adhesion-formation (scar tissue) in deschending frequency order.

A
  • Appendectomy
  • Colorectal surgery
  • Gynecological procedures
  • UGI procedures

*Lower abdominal and pelvic surgeries lead to obstruction more often than UGI surgeries.

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11
Q

What are the three general classifications of obstruction? What do these classifications depend on?

A
  • Simple obstruction, closed loop obstruction and strangulation.
  • Depends on type of obstruction process and it’s method of obstruction
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12
Q

Examples of simple obstruction?

A

Cancer, adhesion

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13
Q

Examples of closed-loop obstruction

A

Volvulus (an obstruction caused by twisting of the stomach or intestine)

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14
Q

Examples of strangulation obstruction

A

Volvulus (an obstruction caused by twisting of the stomach or intestine) and adhesions (scar tissue)

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15
Q

Postoperative adhesions can cause acute obstruction. How long after surgery does this occur?

A
  • Within 4 weeks
  • Or a chronic obstruction which develops slowly and may occur decades later
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16
Q

More _______ are performed now with an accompanying rise in adhesion-related SBO.

A

laparotomies

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17
Q

What will an adhesion that is growing in a manner that traps or occludes a portion of bowel most likely creat?

A

A simple obstruction.

*One that is obstructed only at one end of the bowel section.

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18
Q

Bowel material can _____ the obstructed area but cannot _____.

A

enter; exit

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19
Q

What is a volvulus and what is it a form of?

A

Twisting of the bowel upon itself and is a form of closed-loop obstruction.

20
Q

What can a volvulus become

A

Necrotic and gangrene develops because the bowel’s blood supply (mesentary) has been twisted into the obstruction so tightly that blood can no longer flow to the area.

21
Q

An obstruction in which blood flow is compromised is known as a(n) ______ ______.

A

strangulation obstruction

22
Q

What is considered a medical emergency?

A

Strangulation whether by adhesions or volvulus

23
Q

The occurrences of volvulus in the western world is more commonly seen as what? Percentage?

A
  • Due to a secondary process
  • most often adhesions
  • 70-90% of all cases of SB volvulus
  • The adhesions serve as a pivot point around which a mobile section of bowel can begin to twist
24
Q

Is a volvulus a life-threatening medical emergency?

A
  • Yes, it carries a mortality rate of 10-35%
  • With gangrene the mortality rate is about 40%
25
Q

The primary form of small bowel volvulus occurs in what age group?

A

Children and young adults

*A very unusual form

26
Q

Secondary small bowel volvulus is uncommon in those under the age of ____, with peak incidence between ___ and ___ years old.

A

40; 60-80

27
Q

Is small bowel volvulus (both primary and secondary) more common in males or females?

A

Males

28
Q

Obstruction of the small bowel leads to what?

A

Dilation of the intestine proximal to the obstructing lesion.

29
Q

Why does obstruction of the small bowel lead to dilation of the intestine proximal to the obstructing lesion?

A

Because normal secretions will continue to accumulate above the obstruction without being able to pass by the obstruction.

30
Q

What does dilation of the intestine lead to?

A

Increased peristalsis (constriction and relaxation of the muscles of the intestine) both above and below the obstructed site as the body attempts to move the obstructed material.

31
Q

What is likely to be present in the early course of the process as the increased peristaltic activity empties the bowel distal to the obstruction?

A

Diarrhea

32
Q

_________ will be the rule if the obstruction persists.

A

Constipation

33
Q

What are the general signs of obstruction?

A
  • Vomiting
  • Abdominal pain
  • Abdominal distention
  • Collicky pain (more prevalent in simple obstruction)
34
Q

List general signs of obstructin from the slide

A
  • Pain/tenderness abdomen
  • Nausea
  • Vomiting (proximal obstruction)
  • Diarrhea (early)
  • Constipation (late)
  • Abdominal distention (more if obstruction is distal)
35
Q

Distended loops of small bowel comtaining gas and fluid can usually be recognized when?

A

Within 3-5 hours of the onset of complete obstruction.

*Acute abdominal series used to evaluate patients condition

36
Q

How will the bowel appear with distended loops of small bowel?

A

All gas proximal to a SBO represents swallowed air. The air filled small bowel loops will be centrally located, and the large bowel will be collapsed and empty.

37
Q

When the small bowel obstruction is more distally located, how will the dilated loops of the bowel appear?

A

To be placed one above the other, upward and to the left, producing teh characteristic stepladder appearance.

38
Q

How does the appearance of SBO look in the erect position?

A

You should see that the interface between the air and fluid accumulations is marked by a sharp, straight line (air/fluid level).

39
Q

More than ___ air-fluid levels distal to the duodenum are considered to be abnormal.

A

2

40
Q

How can the site of obstruction be predicted?

A

If the number and position of dilated bowel loops are analyzed.

41
Q

What does the presence of a few dilated loops located high in teh abdomen indicate?

A

An obstruction in the distal duodenm or jejunum.

42
Q

The involvement of more SB loops indicates what?

A

A more distal obstruction, such as you see in an image on slide 12.

43
Q

How much gas is found in a patient with a complet mechanical SBO?

A
  • Little or no gas is found in the large bowel
  • This is a valuable point in determining whther the air-fluid accumulation is due to a mechanical cause or to an adynamic ileus.
44
Q

Why would it be necessary to do a barium enema be done instead of just an acute abdominal series?

A

An AAS may not be adequate to demosntrate which segment of bowel is involved or whether it is a small bowel or large bowel process.

45
Q

If it is necessary to specifically locate a givn site in teh SBO, ______ administered by _____ is hte most effective method.

A

barium; mouth

*Water soluble contrast agents are not recommended orally because the build up of fluids in the bowel that is part of the obstructive process will dilute the contrast.

46
Q

What is the effect of SBO on radiographic technique?

A
  • Large air accumulations are easily penetrated making this a destructive pathology.
  • Decrease kVp by 6-10.

Radiologic Pathologies 3461 (28 decks)

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