Large Bowel Obstruction (Abdomen and Pelvis)

Question 1

Diameter of the cecum that is high risk for perforation with attendant risk of peritonitis and septic shock.

Answer 1

When the cecum exceeds 10 cm in diameter

Question 2

Most colonic obstruction occur where?

Answer 2

Sigmoid colon, where the bowel lumen is narrower and stool is more formed

Question 3

In what situation would the colon decompress into the ileum and jejunum, and the risk of perforation of the cecum is reduced?

Answer 3

Incompetent ileocecal valve

Question 4

Air-fluid levels distal to the hepatic flexure are strong evidence of obstruction, unless in what situation?

Answer 4

Patient had enema

Question 5

Three lines of the sigmoid volvulus are formed by?

Answer 5

Formed by the lateral walls of the loop and the summation of the two opposed medial walls of the loop converge inferiorly into the left iliac fossa

Question 6

Barium enema demonstrates obstruction (sigmoid volvulus) that tapers to a beak at the point of the twist, usually approximately how many cm above the anal verge?

Answer 6

15 cm above the anal verge

Question 7

A radiologic sign that the apex of the distended sigmoid colon may extend cephalad to the transverse colon. Seen in sigmoid volvulus.

Answer 7

Northern exposure sign

Question 8

CT findings of sigmoid volvulus includes:

Answer 8

1. Inverted, dilated, U-shaped sigmoid colon
2. Absence of gas in the rectum
3. Transition zones between dilated and collapsed bowel occur at the point of twisting
4. Oblique lines created by the orientation of the transition zones creat the “x-marks the spot sign” appreciated on sequential images
5. Single beak-shaped transition point

Question 9

Most common type of cecal volvulus.

Answer 9

Twist and invert - with the cecum displaced to the left upper quadrant

Question 10

Axial twist of the cecum about the long axis of the ascending colon results what position of the cecum?

Answer 10

The cecum remains in the right lower quadrant.

Question 11

It refers to the folding of the cecum to a position anteromedial to the ascending colon.

Answer 11

Cecal bascule - accounts for about one-third of the cases.

Question 12

What is the most common cause of large bowel obstruction in elderly and bedridden patients?

Answer 12

Fecal impaction

Question 13

What would be the next step after fecal disimpaction?

Answer 13

Colonoscopy or barium enema to search for an obstructing carcinoma that may have cause the fecal impaction

Question 14

It is a clinical disorder of acute colonic distension with abdominal pain and distension but without the presence of mechanical obstruction.

Answer 14

Colonic pseudoobstruction or Ogilvie syndrome

Question 15

Pathophysiology of colonic pseudoobstruction.

Answer 15

Uncertain. Most current theories favour imbalance in autonomic innervation of the colon