Bowel Obstruction / Ileus |
Dilated bowel may be from:
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What are the radiological findings of paralytic ileus?
- Distended bowel with multiple air-fluid levels
- Gas seen in the rectum
How is bowel obstruction different from paralytic ileus?
- There will be paucity of gas in bowel beyond the site of obstruction, unlike in paralytic ileus where gas can be seen in the rectum.
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What are the common causes of paralytic ileus?
- Paralytic ileus occurs when there is inflammation in the peritoneum, most often following abdominal surgery, or other inflammations, like appendicitis, pancreatitis, etc.
- Normal postoperative ileus lasts 48 hours.
- The absence of bowel sounds, flatus, or bowel movements beyond the expected period indicates delayed resolution or bowel obstruction.
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What are the common causes of small bowel obstruction?
- Post-op adhesions
- Gallstone ileus
- Intussusception
- Tumors
What are the common causes of large bowel obstruction?
- Cancer colon
- Fecal impaction
- Diverticulitis
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What are the useful imaging procedures in the evaluation of bowel obstruction?
- Plain film serves as a screening procedure to detect bowel obstruction.
- Supine and erect films are often done to look for dilated loops of bowel and air fluid levels.
- However, comparing various studies of the efficacy of plain abdominal films in working up SBO show a wide range of sensitivity and specificity.
- Sensitivities ranged from 41 to 86% and specificities range from 25 to 88%.
- CT abdomen provides detailed information including the possible etiology for obstruction.
- CT with PO and IV contrast has a sensitivity and specificity of 100 and 83%. If the bowel is ischemic, then specificity decreases to 61%.
- Lower GI is rarely done nowadays.
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What are the radiological findings of small bowel obstruction?
The characteristics of small bowel obstruction include:
- Multiple air-fluid levels
- Stacked
- Centrally located loops of intestine
- Dilated small bowel greater than 3 cms visible with valvulae conniventes.
- String of pearl sign caused by slow resorption of intraluminal air leaving small air bubbles trapped between valvulae conniventes
- Absence or paucity of colon gas: Collapsed colon
What are the radiological findings of large bowel obstruction?
- Obstructed colon usually appears as a peripherally located distended bowel with haustral markings.
- No air distal to site of obstruction.
- Sometimes the mass may be seen.
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How do you distinguish small from large bowel?
- Small bowel is in the central abdomen.
- Large bowel is in the periphery of abdomen.
- Valvulae Conniventes crosses the entire width of small bowel.
- Haustra are seen partially across the width of large bowel.
- Bubbly appearance of feces indicates large bowel.
- Diverticula are present only in large bowel.
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Image Atlas for Bowel Obstruction / Ileus |
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CT With GI Contrast
Normal Bowel
- Large bowel is identified by the sacculations called haustra scattered all along the colon.
- The colon has fat filled tags called appendices epiploicae on its surface.
- These haustra and epiploicae separate the large from the small intestine.
- Colon is filled with feces which has bubbly appearance
- The small bowel is located in the center of abdomen.
- Fairly narrow about 2.5 cm tube like structure winds compactly back and forth within the abdominal cavity.
- The small intestine is identified by valvulae circulares or circular folds on oral contrast study.
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Plain film in a case with Small bowel obstruction
Post-Op Paralytic Ileus
- Multiple dilated small bowel loops are seen (white arrowheads).
- There is fecal material in the right and left colon
(arrows).
- Air is seen in the rectum.
- The surgical staples indicate recent abdominal surgery. (black arrowheads).
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Small bowel obstruction
Cross lateral view shows multiple dilated fluid filled loops of bowel with air fluid levels. |
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Small bowel obstruction
Absence or paucity of colon gas |
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CT scan of another patient showing findings of small bowel obstruction:
- Post-op changes in abdominal wall
Arrowheads: Normal size of distal small bowel and rectosigmoid (RS)
- Arrowheads: Dilated small bowel loops
Arrow: Area of obstruction
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Small bowel obstruction
Gallstone Ileus
- Air in bile duct
- Dilated small bowel
- Gallstone is not seen in this film and may overlie the sacrum where the dilated bowel seems to end (black arrow)
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Lower GI in a patient with Large bowel Obstruction
- Dilated bowel loops proximal to the obstruction
- Arrow points to the etiology of obstruction
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