Intestinal obstruction

Question 1

What is mechanical bowel obstruction?

Answer 1

interruption of normal passage through the bowel due to a structural barrier (e.g., a tumor, adhesions)

Question 2

What is paralytic ileus?

Answer 2

Temporary disturbance of peristalsis in absence of mechanical obstruction
(functional bowel obstruction)

Question 3

How may intestinal obstruction be classified?

Answer 3

Small or Large bowel
Partial or Complete obstruction
Simple or Strangulated
Extramural, intramural or intraluminal

Question 4

List 3 causes of extramural bowel obstruction

Answer 4

Hernia (SB)
Adhesions (SB)
Volvulus (LB)

Question 5

List 4 causes of intramural bowel obstruction

Answer 5

Tumours: Single or Multifocal (LB)
Inflammatory strictures (e.g. IBD)
Diverticular strictures (LB)
Intussusception

Question 6

List 3 causes of intraluminal bowel obstruction

Answer 6

Pedunculated tumours
Foreign body (e.g. bezoars, gallstones)
Faecal impaction

Question 7

Describe the epidemiology of intestinal obstruction

Answer 7

COMMON
More common in ELDERLY due to increased incidence of adhesions, hernias + malignancy

Question 8

What are the most common causes of SBO?

Answer 8

ADHESIONs
Incarcerated herniad

Question 9

What are the most common causes of LBO?

Answer 9

TUMOURS
Diverticular disease
Volvulus

Question 10

Describe complete BO

Answer 10

Total obstruction of intestinal lumen, preventing passage of air + fluid
Rapid progression of clinical features
Obstipation (complete inability to pass stool/ gas)

Question 11

Describe partial BO

Answer 11

Partial obstruction of intestinal lumen, allowing a small amount of air + fluid through
Clinical features less severe than in complete BO
Intermittent passage of flatus + overflow diarrhoea

Question 12

List 5 symptoms of intestinal obstruction

Answer 12

Severe abdo pain
Abdo distension
N+V (may be bile-stained or faeculent)
Absolute constipation
Decreased/ tinkling bowel sounds

Question 13

Describe pain, vomiting, constipation and distension in SBO

Answer 13

Colicky central abdo pain
Early onset vomiting, bilious, may occur before constipation
Late onset constipation
Distension less severe than LBO

Question 14

Describe pain, vomiting, constipation and distension in LBO

Answer 14

Pain colicky or constant
Late onset vomiting, initially bilious, then faecal
Early onset constipation
Early + significant distension

Question 15

List 4 signs of bowel obstruction

Answer 15

Dehydration +/- hypovolemia (hypotension, dry mucous membranes)
Diffuse abdominal tenderness
Tympanic percussion
Tinkling/ absent bowel sounds

Question 16

What is complicated bowel obstruction?

Answer 16

BO a/w strangulation, ischaemic necrosis or perforation

Question 17

Describe initial management in suspected BO

Answer 17

A-E approach
Obtain IV access
IV fluid resus +/- electrolytes
NBM
NG tube with free drainage
Analgesia
Antiemetics
Obtain imaging

Question 18

Describe choice of imaging modality in suspected BO

Answer 18

Stable: CT AP with IV contrast (definitive, GS)
Unstable: AXR

Question 19

Describe imaging in SBO

Answer 19

Dilated bowel >3cm, predominantly central
Valvulae conniventes (completely cross the lumen)
No gas in large bowel
Air-fluid level

Question 20

Describe imaging in LBO

Answer 20

Dilated bowel >6cm or >9cm if at caecum
Dilated loops predominantly peripheral
Haustra which don’t cross whole lumen width
Air-fluid level

Question 21

Describe what management of BO depends on

Answer 21

Urgency of Mx depends on whether perforation is suspected
If cause of obstruction itself does not require surgery, conservative Mx for 72h can be trialled

Question 22

What further management may be required in BO?

Answer 22

IV abx if perforation suspected/ surgery planned
Exploratory laparotomy: irrigation, resection + address underlying cause

Question 23

In which cases is surgical management considered for BO?

Answer 23

Complicated BO
Closed loop obstruction
Strangulation
Haemodynamic instability not responding to fluids
Underlying cause necessitates e.g. tumour
Refractory to conservative Mx

Question 24

List 4 complications of intestinal obstruction

Answer 24

Dehydration
Bowel perforation leading to peritonitis
Toxaemia (blood poisoning)
Gangrene of ischaemic bowel wall

Question 25

What is the prognosis for intestinal obstruction?

Answer 25

Variable
Dependent on the general state of the patient + prevalence of complications

Question 26

How does Gallstone Ileus occur?

Answer 26

When a stone erodes through the gallbladder into the duodenum, forming a cholecysto-duodenal fistula
= mechanical obstruction caused by an impacted gallstone in the small bowel

Question 27

Which obstructions can be managed conservatively (at least initially)?

Answer 27

Post-op ileus
Partial BO

Question 28

What interventional measures may be used in BO?

Answer 28

Emergency laparotomy
Endoscopic removal/ fragmentation of obstruction
Stool evacuation

Question 29

What should you look out for when suspecting intestinal obstruction?

Answer 29

Hernias 
Abdo scars: previous abdo surgery increases risk of adhesions 
Abdo mass (e.g. intussusception, carcinoma)

Question 30

What bloods should be taken in suspected intestinal obstruction?

Answer 30

FBC: high WCC, anaemia in Ca
CRP: HIGH
U+E's: deranged due to vomiting
Glucose (Exclude DKA)
G+S

Question 31

What is it important to monitor in patients with intestinal obstruction?

Answer 31

Electrolyte changes
3rd space losses (causes dehydration)

Question 32

What may cause a metabolic alkalosis in intestinal obstruction?

Answer 32

Hypokalaemia due to vomiting
Sequestration of fluid in distended bowel loops (3rd spacing) causing dehydration

Question 33

What may cause a metabolic acidosis in intestinal obstruction?

Answer 33

Anaerobic metabolism by ischaemic cells producing lactic acid
Lysis of ischaemic cells releasing intracellular K+