Bowel obstruction / Ileus

What are the sites of bowel obstruction?

• Small bowel
• Large bowel

What is ileus?

Dilated bowel which may be from:

• Paralytic
• Obstructive

What are the common causes of 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 obstructed ileus.

What are the radiological findings of ileus?

• Distended bowel with multiple air-fluid levels
• Gas seen in the rectum

How is it different from bowel obstruction?

• 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.
• Distended bowel loops proximal to site of obstruction. This will depend on whether it is small bowel or large bowel obstruction.
• Air fluid levels noted in bowel.

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.

What are the radiological findings of small bowel obstruction?

The characteristics of small bowel obstruction include:

• Multiple air-fluid levels in dilated centrally located loops of intestine with
• Visible valvulae conniventes
• Absence or paucity of colon gas

Absence or paucity of colon gas

What are the common causes of small bowel obstruction?

• Post-op adhesions
• Gallstone ileus
• Intussusseption
• Tumors

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.

What are the common causes of large bowel obstruction?

• Cancer colon
• Fecal impaction
• Diverticulitis

Small bowel obstruction 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).

Small bowel obstruction Cross lateral view shows multiple dilated fluid filled loops of bowel with air fluid levels.

A: The arrow points to post op changes in the abdominal wall. Arrowheads point to the normal size of distal small bowel and recto-sigmoid (RS). B: Arrowheads point to dilated small bowel loops. The arrows point to the area of obstruction.

Large bowel Obstruction Dilated bowel loops proximal to the obstruction Arrow points to the etiology of obstruction.