Small and large bowel obstruction

Question 1

Definition

Answer 1

Partial or complete blockage of the small or large intestine preventing normal flow of gastrointestinal content

Question 2

What is a closed loop obstruction?

Answer 2

SURGICAL EMERGENCY

2nd obstruction proximally, such as volvulus or competent ileocaecal valve in large bowel obstruction – bowel will continue to extend until ischaemia or perforation

Question 3

Is small or large bowel obstruction more common?

Answer 3

Small - accounts for 80% intestinal obstruction

Question 4

How common?

Answer 4

Account for 15% acute abdomens

Question 5

Who’s affected?

Answer 5

can occur at any age

Question 6

What happens in bowel obstruction?

Answer 6

Mechanical or functional obstruction –> gross dilation of proximal bowel –> increased peristalsis of bowel –> secrete large volumes of electrolyte rich fluid (third spacing) –> can lead to hypovolaemia

Question 7

Most common causes of bowel obstruction

Answer 7

ADHESIONS (small bowel)
HERNIAS (small bowel)
MALIGNANCY (large bowel)
Diverticular disease (large bowel)
Volvulus (large bowel)

Adhesions, hernias and malignancy account for 90%

Question 8

Mechanical obstruction

Answer 8

Physical blockage, obstruction is either simple, closed loop or strangulated

Most common = adhesions (usually post-surgery)

Other causes = hernias, volvulus, tumours, diverticular disease/strictures, inflammatory strictures (e.g. secondary to Crohn’s), intussusception (children), constipation/impacted faeces, foreign body

Question 9

Functional obstruction

Answer 9

Adynamic bowel due to absence of normal peristaltic contractions (neuromuscular dysfunction)

Paralytic ileus
Mesenteric vascular occlusion
Medication related e.g. opioid

Question 10

Risk factors

Answer 10

• Hx of abdominal surgery (–> adhesions)
• Hx of hernia
• Cancer
• IBD
• Hx of foreign body ingestion

Question 11

Symptoms/history

Answer 11

VOMITING (esp. green bilious) – early in SBO, late in LBO

ABDOMINAL DISTENTION

Diffuse ABDOMINAL PAIN – colicky, cramping (constant or worse on movement = red flag for ischaemia)

ABSOLUTE CONSTIPATION (no stool or flatus) – early in LBO, late in SBO

Question 12

Signs/examination

Answer 12

Abdominal distention

Abdominal tenderness

Tinkling bowel sounds (decreased bowel sounds in functional obstruction)

Tympanic sounds on percussion

Evidence of underlying cause e.g. surgical scars, cachexia, hernia

Dehydration –> hypotension, tachycardia

Question 13

Differentials

Answer 13

• Gastroenteritis
• Gut perforation
• Toxic megacolon

Question 14

Investigations

Answer 14

BLOODS: U&Es, FBC, CRP, LFTs, G&S

VBG: lactate increased in bowel ischaemia, assess for metabolic derangement secondary to dehydration or excessive vomiting e.g. metabolic alkalosis due to vomiting

ABDOMINAL CT WITH IV CONTRAST: confirm diagnosis, establish site and cause of obstruction

PLAIN ABDOMINAL X-RAY

ERECT CXR: assess for free air under diaphragm suggesting bowel perforation

WATER SOLUBLE ENEMA (GASTROGRAFIN): may help demonstrate site of obstruction (aka contrast fluoroscopy). Used in small bowel obstruction caused by adhesions to determine likelihood of obstruction resolving without surgery

Question 15

Signs of AXR

Answer 15

Small bowel: dilated >3cm, central abdo location, valvulae conniventes

Large bowel: dilated >6cm (or >9cm if at caecum), peripheral location, haustral lines

Bowel proximal to obstruction dilated and filled with air, bowel distal to obstruction collapsed with absent gas
Gas seen throughout bowel in functional obstruction

Question 16

Management

Answer 16

Drip and suck (conservative) management
Surgery 
Anti-emetics
Analgesia
Consider Abx prophylaxis

Question 17

Drip and suck management

Answer 17

• Nil by mouth
• Nasogastric tube to decompress bowel
• IV fluids for hydration and correction of electrolytes
• Catheterise to monitor fluid balance
• Usually resolves after a few days

Question 18

Indications for surgery

Answer 18

closed loop obstruction
ischaemia
strangulated hernia
obstructing tumour
no improvement with conservative management (>48hrs)

Question 19

Examples of surgery

Answer 19

adhesiolysis
hernia repair
emergency resection of obstructing tumour
inserting stent if obstructing tumour

Question 20

Prognosis

Answer 20

Mortality 25% in SBO if surgery delayed beyond 36hrs (8% if under 36hrs)

50% sigmoid volvulus recur within 2yrs

Question 21

Prognosis

Answer 21

Mortality 25% in SBO if surgery delayed beyond 36hrs (8% if under 36hrs)

50% sigmoid volvulus recur within 2yrs

Question 22

Complications

Answer 22

Bowel perforation and/or ischaemia –> peritonitis, septicaemia

Dehydration/fluid and electrolyte imbalance –> AKI

Question 23

Explaining bowel obstruction to patient

Answer 23

So we think that the cause of your stomach pain is a bowel obstruction - I’ll now try and explain this to you. So normally your intestines are a tube where the food you eat and the fluid you drink passes through. In bowel obstruction, there is something blocking this flow within the tube so your stomach contents can no longer pass through and this is what is causing your symptoms. Many different things can cause there to be an obstruction, and we would like to take some bloods and do some scans to try and work out what is causing this so that we can treat it.