Mod 5-2 SBO Flashcards
What is small bowell obstruction considered to be?
The most common disorder of the small intestine requiring surgical intervention to correct.
How does an obstruction occur?
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
List mechanical processes that are responsible for SBO and their frequency.
- 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%
What would an example of a non-mechanical obstruction be?
An ileus which is a lack of peristaltic activity and not a true obstructive process.
What are the three forms of a mechanica obstruction?
- Simple obstruction
- Closed loop obstruction
- Strangulation
What is a simple obstruction?
When only the intestinal lumen is occluded
What is a closed loop obstruction?
- 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.
What is strangulation?
When the blood supply is impaired resulting in necrosis of the bowel wall.
*Can be caused by closed loop obstruction
What is the number one cause of SBO in developing countries such as the U.S.?
Postoperative adhesions (60-75%)
List the surgeries closely associated with SBO and related adhesion-formation (scar tissue) in deschending frequency order.
- Appendectomy
- Colorectal surgery
- Gynecological procedures
- UGI procedures
*Lower abdominal and pelvic surgeries lead to obstruction more often than UGI surgeries.
What are the three general classifications of obstruction? What do these classifications depend on?
- Simple obstruction, closed loop obstruction and strangulation.
- Depends on type of obstruction process and it’s method of obstruction
Examples of simple obstruction?
Cancer, adhesion
Examples of closed-loop obstruction
Volvulus (an obstruction caused by twisting of the stomach or intestine)
Examples of strangulation obstruction
Volvulus (an obstruction caused by twisting of the stomach or intestine) and adhesions (scar tissue)
Postoperative adhesions can cause acute obstruction. How long after surgery does this occur?
- Within 4 weeks
- Or a chronic obstruction which develops slowly and may occur decades later
More _______ are performed now with an accompanying rise in adhesion-related SBO.
laparotomies
What will an adhesion that is growing in a manner that traps or occludes a portion of bowel most likely creat?
A simple obstruction.
*One that is obstructed only at one end of the bowel section.
Bowel material can _____ the obstructed area but cannot _____.
enter; exit
What is a volvulus and what is it a form of?
Twisting of the bowel upon itself and is a form of closed-loop obstruction.
What can a volvulus become
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.
An obstruction in which blood flow is compromised is known as a(n) ______ ______.
strangulation obstruction
What is considered a medical emergency?
Strangulation whether by adhesions or volvulus
The occurrences of volvulus in the western world is more commonly seen as what? Percentage?
- 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
Is a volvulus a life-threatening medical emergency?
- Yes, it carries a mortality rate of 10-35%
- With gangrene the mortality rate is about 40%
The primary form of small bowel volvulus occurs in what age group?
Children and young adults
*A very unusual form
Secondary small bowel volvulus is uncommon in those under the age of ____, with peak incidence between ___ and ___ years old.
40; 60-80
Is small bowel volvulus (both primary and secondary) more common in males or females?
Males
Obstruction of the small bowel leads to what?
Dilation of the intestine proximal to the obstructing lesion.
Why does obstruction of the small bowel lead to dilation of the intestine proximal to the obstructing lesion?
Because normal secretions will continue to accumulate above the obstruction without being able to pass by the obstruction.
What does dilation of the intestine lead to?
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.
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?
Diarrhea
_________ will be the rule if the obstruction persists.
Constipation
What are the general signs of obstruction?
- Vomiting
- Abdominal pain
- Abdominal distention
- Collicky pain (more prevalent in simple obstruction)
List general signs of obstructin from the slide
- Pain/tenderness abdomen
- Nausea
- Vomiting (proximal obstruction)
- Diarrhea (early)
- Constipation (late)
- Abdominal distention (more if obstruction is distal)
Distended loops of small bowel comtaining gas and fluid can usually be recognized when?
Within 3-5 hours of the onset of complete obstruction.
*Acute abdominal series used to evaluate patients condition
How will the bowel appear with distended loops of small bowel?
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.
When the small bowel obstruction is more distally located, how will the dilated loops of the bowel appear?
To be placed one above the other, upward and to the left, producing teh characteristic stepladder appearance.
How does the appearance of SBO look in the erect position?
You should see that the interface between the air and fluid accumulations is marked by a sharp, straight line (air/fluid level).
More than ___ air-fluid levels distal to the duodenum are considered to be abnormal.
2
How can the site of obstruction be predicted?
If the number and position of dilated bowel loops are analyzed.
What does the presence of a few dilated loops located high in teh abdomen indicate?
An obstruction in the distal duodenm or jejunum.
The involvement of more SB loops indicates what?
A more distal obstruction, such as you see in an image on slide 12.
How much gas is found in a patient with a complet mechanical SBO?
- 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.
Why would it be necessary to do a barium enema be done instead of just an acute abdominal series?
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.
If it is necessary to specifically locate a givn site in teh SBO, ______ administered by _____ is hte most effective method.
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.
What is the effect of SBO on radiographic technique?
- Large air accumulations are easily penetrated making this a destructive pathology.
- Decrease kVp by 6-10.
