Intestinal Obstruction

Question 1

What are most intestinal obstructions due to.

Answer 1

Due to mechanical block.

Question 2

What is a common occurrence after abdominal surgery.

Answer 2

Paralytic ileus.

Question 3

What are some causes of small bowel obstruction. (5)

Answer 3

Adhesions (80% in adults). 
Hernias. 
Crohn's disease. 
Intessusception. 
Obstruction due to extrinsic involvement by cancer.

Question 4

What are some causes of colonic obstruction. (4)

Answer 4

Carcinoma of the colon.
Sigmoid or caecal volvulus.
Diverticular disease (strictures).
Constipation.

Question 5

What are the cardinal features of intestinal obstruction. (4)

Answer 5

Vomiting.
Colicky pain.
Constipation.
Distension.

Question 6

What is the most common cause of small bowel obstruction.

Answer 6

Adhesions.

Question 7

What are the rare causes of bowel obstruction. (5)

Answer 7

Crohn's disease. 
Gallstone ileus. 
Intussusception. 
TB (developing world). 
Foreign body.

Question 8

What occurs in established intestinal obstruction.

Answer 8

Fermentation of the intestinal contents causes ‘faeculent’ vomiting.

Question 9

What sound is typically heard on auscultation of an obstructed bowel.

Answer 9

Tinkling bowel sounds.

Question 10

What is seen on AXR in small bowel obstruction. (3)

Answer 10

Central gas shadows with valvulae conniventes that completely cross the lumen.
No gas in the large bowel.

Question 11

What is seen on AXR in large bowel obstruction. (3)

Answer 11

Peripheral gas shadows proximal to the blockage (eg in caecum).
No gas in the rectum (unless introduced by PR exam).
Large bowel haustra do not cross all the lumen’s width.

Question 12

What distinguishes small bowel obstruction from large bowel obstruction. (3)

Answer 12

In small bowel obstruction, vomiting occurs earlier.
There is less abdominal distention.
Pain is higher in the abdomen.

Question 13

What are the features of ileal bowel obstruction. (3)

Answer 13

Functional obstruction from reduced bowel motility.
No pain.
BS are absent.

Question 14

What is a simple bowel obstruction. (2)

Answer 14

One obstructing point.

No vascular compromise.

Question 15

What is a closed loop bowel obstruction. (3)

Answer 15

Obstruction at two points forming a loop of grossly distended bowel.
At risk of perforation.
>12cm requires urgent decompression.

Question 16

What is a strangulated bowel obstruction. (7)

Answer 16

Blood supply is compromised.
The patient is more ill than you would expect.
There is sharper, more constant and LOCALISED pain.
Peritonism if a cardinal sign.
There may be fever, raised WCC and other signs of mesenteric ischaemia.

Question 17

What must occur for there to be complete bowel obstruction. (2)

Answer 17

No passage of stools or flatus.

Question 18

What symptom may be absent in lower bowel obstruction.

Answer 18

Vomiting.

Question 19

What are the physical signs of bowel obstruction. (2)

Answer 19

Abdominal distention.

Tinkling or absent bowel sounds.

Question 20

What does marked abdominal tenderness suggest on an abdominal exam.

Answer 20

Strangulated bowel obstruction.

Question 21

What other areas must be examined in a patient with a bowel obstruction. (2)

Answer 21

Hernial orifices.

Rectum.

Question 22

What is the investigation of choice in bowel obstruction.

Answer 22

CT - as it can localize the lesion accurately.

Question 23

What is acute colonic pseudo obstruction. (2)

Answer 23

A clinical picture mimicking mechanical obstruction.

Management is by withdrawing the underlying problem (eg opates, analgesics).