Intestinal Obstruction Flashcards
definition?
failure of downward passage of intestinal contents
classifications?
- dynamic vs adynamic
- dynamic: increased peristalsis acting against obstructing agent
- adynamic: peristalsis absent or ineffective
- simple vs strangulating
- simple: obstruction of lumen but blood supply not compromised
- strangulating: obstruction of lumen w blood supply compromised
causes of simple?
- in lumen
- gallstone
- impacted faeces
- in wall
- strictures
- outside wall
- adhesions
- tumours
- hernias
pathophysiology of obstruction
- above obstruction- peristalsis & distension
- at site of obstruction- perforation
- below- collapsed and pale
key concepts?
- 3rd space fluid loss –> dehydration
- proliferation of bacteria proximal to obstruction
- impairment of barrier function of intestinal mucosa
- death caused by:
- peritonitis
- fluid & electrolyte imbalance
what is it important to remember about strangulated bowel obstruction?
have window of about 6hrs to act before bowel becomes necrotic and dies
causes of strangulation?
- strangulated hernia
- intususception
- volvulus
- vascular occlusions
- adhesive intestinal obstruction
pathophysiology of strangulation?
- venous return impaired
- serosanguinus fluid formation
- arterial supply impaired
what is closed loop obstruction?
- some part of the bowel is closed at both ends
- this is physiological, unless incompetent IC valve
- makes bowel prone to perforation
which part of bowel is most prone to perforation?
caecum- as this is thinnest part
- If 10cm or approaching, risk of imminent perforation –> requires urgent surgery
Symptoms of bowel obstruction?
PV D&C
Pain
Vomiting
Distension
Constipation
in which order would they present in small / large bowel obstruction?
- SBO
- top down (pain–>constipation)
- LBO
- bottom up (constipation–>pain)
describe the features of pain
- generalised abdo colicky pain
- each attack lasts a few mins then gradually disappears
- in between attacks, periods of relief
- as time passes, pain becomes more severe, more frequent and stays for longer
describe vomiting
higher up the obstruction, the earlier and more severe vomiting is
describe constipation
- in complete –> absolute constipation
- in partial–> continued passage of flatus and/or stool beyond 6-12hrs after onset of symptoms
cases that present without absolute constipation?
- richters hernia
- gallstone ileus
- mesenteric vascular occlusion
describe distension
- SBO
- flanks collapsed as no air in colon
- LBO w competent IC valve
- distended flanks
- LBO w incompetent IC valve
- generalised distension
what is Richter’s hernia?
- herniation of anti-mesenteric wall of bowel, usually through a small defect
- 10% of strangulated hernias
- progress more rapidly to gangrene than other types of strangulated hernias because they are v small- v important to not miss!!
signs of bowel obstruction? general and local
- general
- dehydration
- tachycardia & shock - suspect strangulation
- local
- no tenderness or rigidity w simple obstruction
- inspect for scars, hernias, visible peristalsis
- late on- silent abdo on auscultation
summary of when to suspect strangulation
internal in abdo
- shock
- pain - more severe & never completely absent in between attacks
- abdo tenderness and rigidity
- NG suction- for 1/2hrs fails to relieve any pain
external- in groin
- hernia swelling that is tense, tender, irreducible & no expansible impulse on cough
Ix for bowel obstruction?
- Bloods
- FBC
- U&E
- LFT
- group and save
- PR
- may reveal cause of obstruction ie tumour, impaction
- AXR
- Erect CXR
- perforation
- CT
- confirm diagnosis if transition point seen
- detection of ischaemia & bowel perforation
when specific investigations can you do for small / large bowel
- Water soluble oral contrast
- done once diagnosis confirmed
- contrast in caecum within 6hrs is predictive of nonsurgical resolution of adhesive small bowel obstruction
- Can occasionally have therapeutic effect
- Water soluble enema
- to confirm diagnosis of LBO
Mx of bowel obstruction?
- drip n suck
- IV fluid resus
- NG tube
- early surgery if:
- obstructed hernia
- suspected strangulation
- SBO in virgin abdo
- failure of conservative mx
- obstructing tumours on CT
DDx?
- constipation
- toxic megacolon
- paralytic ileus
