Intestinal Obstruction

Question 1

Define “intestinal obstruction”

Answer 1

when normal flow of intestinal contents is interrupted. Classified pathologically into mechanical (dynamic) or fxnal (adynamic)

Question 2

Name the different ways in which I/O can be classified

Answer 2

a) pathological - dynamic vs adynamic
b) anatomical - small bowel (high/low) vs large bowel
c) clinical - acute vs chr vs acute on chr vs sub-acute
d) pathological changes - simple vs strangulated

Question 3

Define “mechanical I/O”

Answer 3

peristalsis is working against a mech obstruction

Question 4

How is mechanical I/O categorized?

Answer 4

intra-luminal
vs intra-mural
vs extra-mural

Question 5

Define “fxnal I/O”

Answer 5

absence of peristalsis w/o obstruction

Question 6

How is fxnal I/O categorized?

Answer 6

absent peristalsis vs pseudo-obstruction

Question 7

What are the causes of absent peristalsis in the intestine?

Answer 7

1) post-operative
2) infxn
3) reflux ileus
4) metabolic

Question 8

What are the causes of pseudo-obstruction of the intestine?

Answer 8

small intestinal pseudo-obstruction (idiopathic/familial visceral myopathy)
acute colonic pseudo-obstruction - toxic megacolon, ogilvie syndrome
chr colonic pseudo-obstruction - hirschsprung ds, paraneoplastic immune mediated (small cell lung Ca)
infxn (Chagas’ ds)

Question 9

How does a pt w/ small bowel obstruction present?

Answer 9

High - early profuse vomiting, rapid dehydration

Low - predominant pain w/ central distention, multiple central fluid levels seen on AXR

Question 10

How does a pt w/ a large bowel obstruction present?

Answer 10

Early + pronounced distention’
Mild pain + vomiting & dehydration = late
Prox colon & caecum distended

Question 11

How does a pt w/ acute I/O present?

Answer 11

Usually small bowel w/ sudden onset colicky central abd pain
Distention
early vomiting + constipation

Question 12

How does a pt w/ chr I/O present?

Answer 12

Usually large bowel obstruction w/ lower abd colic + obstipation followed by distention

Question 13

How does a pt w/ acute on chr I/O present?

Answer 13

short hx of distention + vomiting against a backdrop of pain + constipation

Question 14

How does a pt w/ sub-acute I/O present?

Answer 14

incomplete obstruction

recurrent attacks of colic relieved by passing flatus/faeces

Question 15

What kind of changes in the bowel could be seen in I/O?

Answer 15

distal collapse
prox dilation
strangulation
simple/closed loop obstruction

Question 16

Discuss the pathogenesis of a distally collapsed bowel

Answer 16

below level of obstruction = normal peristalsis + absorption until colon empty -> contract + become immobile

Question 17

Discuss the pathogenesis of prox dilated bowel

Answer 17

initial prox peristalsis increased to overcome obstruction
If obstruction not relieved -> dilation + absent peristalsis
Gas accumulation (anaerobic + aerobic bacterial overgrowth)
Fluid accumulation (impaired absorption)

Question 18

Discuss the pathogenesis of a strangulated bowel

Answer 18

compromised venous return d/t dilated bowel -> increased cap pressure -> local mural distention d/t fluid + cellular exudation -> compromised artery supply -> haemorrhagic infarction -> peritonitis + septicaemia -> hypovolaemic shock

Question 19

What are the clinical features of a strangulated bowel

Answer 19

blood supply compromised
sharper + more constant localised pain
peritonism = cardinal sign
possible fever, raised WCC + signs of mesenteric ischaemia

Question 20

Discuss the pathogenesis of simple and closed loop bowel obstruction

Answer 20

simple: one obstructive pt, no vascular compromise
closed: obstruct @ 2 pts forming a loop of grossly distended bowel - @ risk for perforation, (tenderness + perforation usually @ caecum) >10cm req urgent decompression

Question 21

What are the clinical fx, pathophysiology, causes of simple + closed loop bowel obstruction?

Answer 21

clinical fx: constant RIF pain, guarding, tenderness, absence of dilated small bowels

pathophysiology: strangulation => venous compromise => oedema => arterial compromise => gangrene + potential perforation
causes: volvulus, herniation of bowel, tight carcinomatous stricture of colon w/ competent ileocecal valve

Question 22

What are the 4 cardinal sx of I/O on hx?

Answer 22

Pain
Vomiting
Abd Distention
Constipation/obstipation

Question 23

Aside from the 4 cardinal sx, what other sx/fx should be considered when taking a hx for I/O?

Answer 23

sx of GIT bleed, infxn
previous surgeries
underlying GIT disorders
RFs for ischaemic bowel: atherosclerotic RH, hrt ds, previous stroke
suspicion of malignancy: LOW, LOA, previous Ca, fam hx of Ca

Question 24

What should be considered on PE in a pt presenting w/ I/O?

Answer 24

Vitals, rehydration status, mental status
Abd abnormalities
Masses/impacted stools on DRE

Question 25

Which investigations should be done for a pt presenting w/ suspected I/O?

Answer 25

Bloods - FBC, U&E/Cr, amylase, ABG, PT/PTT
AXR, KUB X-ray
CT Abdo
CT Colonoscopy
barium enema in certain cases
NB crossmatch and ECG for surgical cases