Intestinal Obstruction

Question 1

definition?

Answer 1

failure of downward passage of intestinal contents

Question 2

classifications?

Answer 2

• 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

Question 3

causes of simple?

Answer 3

• in lumen
  
  • gallstone
  • impacted faeces
• in wall
  
  • strictures
• outside wall
  
  • adhesions
  • tumours
  • hernias

Question 4

pathophysiology of obstruction

Answer 4

• above obstruction- peristalsis & distension
• at site of obstruction- perforation
• below- collapsed and pale

Question 5

key concepts?

Answer 5

• 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

Question 6

what is it important to remember about strangulated bowel obstruction?

Answer 6

have window of about 6hrs to act before bowel becomes necrotic and dies

Question 7

causes of strangulation?

Answer 7

• strangulated hernia
• intususception
• volvulus
• vascular occlusions
• adhesive intestinal obstruction

Question 8

pathophysiology of strangulation?

Answer 8

1. venous return impaired
2. serosanguinus fluid formation
3. arterial supply impaired

Question 9

what is closed loop obstruction?

Answer 9

• some part of the bowel is closed at both ends
• this is physiological, unless incompetent IC valve
• makes bowel prone to perforation

Question 10

which part of bowel is most prone to perforation?

Answer 10

caecum- as this is thinnest part

• If 10cm or approaching, risk of imminent perforation –> requires urgent surgery

Question 11

Symptoms of bowel obstruction?

Answer 11

PV D&C

Pain

Vomiting

Distension

Constipation

Question 12

in which order would they present in small / large bowel obstruction?

Answer 12

• SBO
  
  • top down (pain–>constipation)
• LBO
  
  • bottom up (constipation–>pain)

Question 13

describe the features of pain

Answer 13

• 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

Question 14

describe vomiting

Answer 14

higher up the obstruction, the earlier and more severe vomiting is

Question 15

describe constipation

Answer 15

• in complete –> absolute constipation
• in partial–> continued passage of flatus and/or stool beyond 6-12hrs after onset of symptoms

Question 16

cases that present without absolute constipation?

Answer 16

• richters hernia
• gallstone ileus
• mesenteric vascular occlusion

Question 17

describe distension

Answer 17

• SBO
  
  • flanks collapsed as no air in colon
• LBO w competent IC valve
  
  • distended flanks
• LBO w incompetent IC valve
  
  • generalised distension

Question 18

what is Richter’s hernia?

Answer 18

• 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!!

Question 19

signs of bowel obstruction? general and local

Answer 19

• 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

Question 20

summary of when to suspect strangulation

Answer 20

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

Question 21

Ix for bowel obstruction?

Answer 21

• 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

Question 22

when specific investigations can you do for small / large bowel

Answer 22

• 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

Question 23

Mx of bowel obstruction?

Answer 23

• 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

Question 24

DDx?

Answer 24

• constipation
• toxic megacolon
• paralytic ileus