Intestinal Obstruction Flashcards
Define “intestinal obstruction”
when normal flow of intestinal contents is interrupted. Classified pathologically into mechanical (dynamic) or fxnal (adynamic)
Name the different ways in which I/O can be classified
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
Define “mechanical I/O”
peristalsis is working against a mech obstruction
How is mechanical I/O categorized?
intra-luminal
vs intra-mural
vs extra-mural
Define “fxnal I/O”
absence of peristalsis w/o obstruction
How is fxnal I/O categorized?
absent peristalsis vs pseudo-obstruction
What are the causes of absent peristalsis in the intestine?
1) post-operative
2) infxn
3) reflux ileus
4) metabolic
What are the causes of pseudo-obstruction of the intestine?
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)
How does a pt w/ small bowel obstruction present?
High - early profuse vomiting, rapid dehydration
Low - predominant pain w/ central distention, multiple central fluid levels seen on AXR
How does a pt w/ a large bowel obstruction present?
Early + pronounced distention’
Mild pain + vomiting & dehydration = late
Prox colon & caecum distended
How does a pt w/ acute I/O present?
Usually small bowel w/ sudden onset colicky central abd pain
Distention
early vomiting + constipation
How does a pt w/ chr I/O present?
Usually large bowel obstruction w/ lower abd colic + obstipation followed by distention
How does a pt w/ acute on chr I/O present?
short hx of distention + vomiting against a backdrop of pain + constipation
How does a pt w/ sub-acute I/O present?
incomplete obstruction
recurrent attacks of colic relieved by passing flatus/faeces
What kind of changes in the bowel could be seen in I/O?
distal collapse
prox dilation
strangulation
simple/closed loop obstruction
Discuss the pathogenesis of a distally collapsed bowel
below level of obstruction = normal peristalsis + absorption until colon empty -> contract + become immobile
Discuss the pathogenesis of prox dilated bowel
initial prox peristalsis increased to overcome obstruction If obstruction not relieved -> dilation + absent peristalsis Gas accumulation (anaerobic + aerobic bacterial overgrowth) Fluid accumulation (impaired absorption)
Discuss the pathogenesis of a strangulated bowel
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
What are the clinical features of a strangulated bowel
blood supply compromised
sharper + more constant localised pain
peritonism = cardinal sign
possible fever, raised WCC + signs of mesenteric ischaemia
Discuss the pathogenesis of simple and closed loop bowel obstruction
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
What are the clinical fx, pathophysiology, causes of simple + closed loop bowel obstruction?
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
What are the 4 cardinal sx of I/O on hx?
Pain
Vomiting
Abd Distention
Constipation/obstipation
Aside from the 4 cardinal sx, what other sx/fx should be considered when taking a hx for I/O?
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
What should be considered on PE in a pt presenting w/ I/O?
Vitals, rehydration status, mental status
Abd abnormalities
Masses/impacted stools on DRE
