Small Bowel Obstruction

Question 1

Extrinsic bowel lesion causes of SBO

Answer 1

Extrinsic bowel causes

• Adhesions: commonest cause, previous laparotomy
• Strangulation in hernia or pockets of abdo cavity
• Volvulus: torsion of bowel around its mesentery
• Masses: extrinsic neoplasm, aneurysm, endometriosis, intra-abdo abscess

Question 2

Intrinsic bowel lesion wall causes of SBO

Answer 2

Intrinsic bowel wall causes:

• Stricture: IBD, irradiation, surgery
• Tumour (rare)
• Intussusception: one part of the bowel is pull into itself by peristalsis (95% in children)

Question 3

Luminal occlusion causes of SBO

Answer 3

• Neoplasm (adenocarcinoma, carcinoid, lymphoma)
• Inflammation: Crohn’s, TB
• Intestinal ischaemia
• Swallowed: foreign body; trichobezoar (hairball)
• Gallstone

Question 4

What is the diagnostic triad of SBO

Answer 4

DxT = colicky central pain + vomiting + distension

Question 5

The more proximal the obstruction, the more ___ the pain

Answer 5

Severe

Question 6

Where is the colicky pain predominantly?

Answer 6

Mainly periumbilical, also epigastric

Question 7

How long do the spasms last for?

Answer 7

Spasms last about 1 minute

Question 8

List the clinical features of SBO

Answer 8

Severe colicky epigastric and perumbilical pain
Spasms app 1 min
Spasms every 3-10 min
Vomiting
Absolute constipation
No flatus (obstipation)
Abdo distension (especially if lower SBO)

Question 9

Difference between high and low SBO: frequency of spasms

Answer 9

High: 3-5 mins
Low: 6-10 mins

Question 10

Difference between high and low SBO: intensity of pain

Answer 10

High: +++
Low: +

Question 11

Difference between high and low SBO: vomiting and content

Answer 11

High: Early, frequent, violent with gastric juices, then green
Low: Later, less severe that is faeculent (later)

Question 12

Difference between high and low SBO: dehydration and degree of illness

Answer 12

High: Marked
Low: Less prominent

Question 13

Difference between high and low SBO: distension

Answer 13

High: Minimal
Low: Marked

Question 14

How will the patient appear on initial inspection?

Answer 14

Patient weak and sitting forward in distress

Question 15

Abdomen is soft on palpation except with ___?

Answer 15

Strangulation

Question 16

Abdomen is tender when ____?

Answer 16

Distended

Question 17

What sounds are heard on auscultation?

Answer 17

Initially there is an increased sharp, tinkling bowel sounds (hyperactive and high pitched). Then later, secondary ileus can occur and eventually bowel can be silent

Question 18

Findings on PR?

Answer 18

Empty rectum, may be tender

Question 19

What x-rays should be ordered and what are the findings?

Answer 19

1. Upright CXR: gas underneath diaphragm
2. Supine AXR: distended loops of bowel > 3cm
3. Upright AXR: air-fluid levels; string of pearls sign

Question 20

Explain the air fluid levels and string of pearls sign on a upright AXR.

Answer 20

Air fluid level: both fluid and gas collect in the intestine, that produce a characteristic ‘air fluid level’ pattern. Air rises above the fluid and there is a flat surface at the ‘air-fluid’ interface
* stepladder fluid levels ‘air-fluid levels’ (4-5 for Dx) in 3-4 hours

String of pearls sign: small pockets of gas in fluid filled small bowel (usually sign of higher grade mechanical obstruction)

Question 21

If Dx by XR is unclear, what should be ordered next?

Answer 21

CT - more sensitive

Question 22

Outline the general pathogenesis of SBO

Answer 22

Small bowel obstruction leads to rapid accumulation of fluid and gas in the bowel proximal to the site of obstruction. In typical cases, there is initial active peristalsis proximal to the obstruction.Within a few hours, the peristaltic activity declines. Oedema and increasing distension supervene. Stasis and bacterial overgrowth make the fluid faeculent. Appearance of faeculent fluid with a foul odour in the vomitus or from a nasogastric tube confirms the diagnosis of obstruction.

Question 23

Rx of SBO

Answer 23

If stable: IV fluids and bowel decompression with NGT
with anti-emetics and analgesics.

Consider surgery if:

• peritonitis or perforation
• Laparotomy or hernia repair

Question 24

Complications of SBO

Answer 24

Increasing severity:

• unable to PO intake (due to vomiting)
• fluid loss into peritoneum (oedema)
• ischaemia and then perforation (in severe cases of oedema)

Question 25

Why is SBO pain epigastric/periumbilical?

Answer 25

small bowel origin is mid gut