Intestinal obstruction Flashcards
What is mechanical bowel obstruction?
interruption of normal passage through the bowel due to a structural barrier (e.g., a tumor, adhesions)
What is paralytic ileus?
Temporary disturbance of peristalsis in absence of mechanical obstruction
(functional bowel obstruction)
How may intestinal obstruction be classified?
Small or Large bowel
Partial or Complete obstruction
Simple or Strangulated
Extramural, intramural or intraluminal
List 3 causes of extramural bowel obstruction
Hernia (SB)
Adhesions (SB)
Volvulus (LB)
List 4 causes of intramural bowel obstruction
Tumours: Single or Multifocal (LB)
Inflammatory strictures (e.g. IBD)
Diverticular strictures (LB)
Intussusception
List 3 causes of intraluminal bowel obstruction
Pedunculated tumours
Foreign body (e.g. bezoars, gallstones)
Faecal impaction
Describe the epidemiology of intestinal obstruction
COMMON
More common in ELDERLY due to increased incidence of adhesions, hernias + malignancy
What are the most common causes of SBO?
ADHESIONs
Incarcerated herniad
What are the most common causes of LBO?
TUMOURS
Diverticular disease
Volvulus
Describe complete BO
Total obstruction of intestinal lumen, preventing passage of air + fluid
Rapid progression of clinical features
Obstipation (complete inability to pass stool/ gas)
Describe partial BO
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
List 5 symptoms of intestinal obstruction
Severe abdo pain
Abdo distension
N+V (may be bile-stained or faeculent)
Absolute constipation
Decreased/ tinkling bowel sounds
Describe pain, vomiting, constipation and distension in SBO
Colicky central abdo pain
Early onset vomiting, bilious, may occur before constipation
Late onset constipation
Distension less severe than LBO
Describe pain, vomiting, constipation and distension in LBO
Pain colicky or constant
Late onset vomiting, initially bilious, then faecal
Early onset constipation
Early + significant distension
List 4 signs of bowel obstruction
Dehydration +/- hypovolemia (hypotension, dry mucous membranes)
Diffuse abdominal tenderness
Tympanic percussion
Tinkling/ absent bowel sounds
What is complicated bowel obstruction?
BO a/w strangulation, ischaemic necrosis or perforation
Describe initial management in suspected BO
A-E approach
Obtain IV access
IV fluid resus +/- electrolytes
NBM
NG tube with free drainage
Analgesia
Antiemetics
Obtain imaging
Describe choice of imaging modality in suspected BO
Stable: CT AP with IV contrast (definitive, GS)
Unstable: AXR
Describe imaging in SBO
Dilated bowel >3cm, predominantly central
Valvulae conniventes (completely cross the lumen)
No gas in large bowel
Air-fluid level
Describe imaging in LBO
Dilated bowel >6cm or >9cm if at caecum
Dilated loops predominantly peripheral
Haustra which don’t cross whole lumen width
Air-fluid level
Describe what management of BO depends on
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
What further management may be required in BO?
IV abx if perforation suspected/ surgery planned
Exploratory laparotomy: irrigation, resection + address underlying cause
In which cases is surgical management considered for BO?
Complicated BO
Closed loop obstruction
Strangulation
Haemodynamic instability not responding to fluids
Underlying cause necessitates e.g. tumour
Refractory to conservative Mx
List 4 complications of intestinal obstruction
Dehydration
Bowel perforation leading to peritonitis
Toxaemia (blood poisoning)
Gangrene of ischaemic bowel wall
What is the prognosis for intestinal obstruction?
Variable
Dependent on the general state of the patient + prevalence of complications
How does Gallstone Ileus occur?
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
Which obstructions can be managed conservatively (at least initially)?
Post-op ileus
Partial BO
What interventional measures may be used in BO?
Emergency laparotomy
Endoscopic removal/ fragmentation of obstruction
Stool evacuation
What should you look out for when suspecting intestinal obstruction?
Hernias Abdo scars: previous abdo surgery increases risk of adhesions Abdo mass (e.g. intussusception, carcinoma)
What bloods should be taken in suspected intestinal obstruction?
FBC: high WCC, anaemia in Ca CRP: HIGH U+E's: deranged due to vomiting Glucose (Exclude DKA) G+S
What is it important to monitor in patients with intestinal obstruction?
Electrolyte changes
3rd space losses (causes dehydration)
What may cause a metabolic alkalosis in intestinal obstruction?
Hypokalaemia due to vomiting
Sequestration of fluid in distended bowel loops (3rd spacing) causing dehydration
What may cause a metabolic acidosis in intestinal obstruction?
Anaerobic metabolism by ischaemic cells producing lactic acid
Lysis of ischaemic cells releasing intracellular K+
