Small Bowel Obstruction Flashcards
What happens to bowel proximal to an obstruction
Becomes dilated with air and fluid
How does an upper SBO present
Acute presentation
Hours of onset
Large volumes of gastric, pancreatic and biliary secretions are regurgitated into the stomach and committed as they can’t pass through the bowel
How does a distal/large bowel obstruction present
Colicky abdominal pain and distension
Vomiting possible faeculent
General symptoms of intestinal obstruction
Vomiting Pain Constipation Distension Complete obstruction Incomplete obstruction
What determines how early vomiting developed
Where the obstruction is
More proximal obstructions - vomiting starts earlier
Can occur even when nothing is taken by mouth as GI secretions continue to be produced and vomited up
Vomitus of semi-digested food eaten a day or to previously with no bile suggests what kind of obstruction
Gastric outlet obstruction
Vomitus of copious amounts of bile-stained fluid suggests what kind of obstruction
Upper small bowel obstruction
vomitus of thick brown, foot smelling ‘faeculent’ fluid
Distal bowel obstruction
What causes the pain in intestine obstruction
Distension of the bowel gives intermittent episodes of colicky pain
How does intestinal obstruction cause constipation
Propulsion of bowel contents stopped
bowel gas is absorbed distal to the obstruction
What is ‘absolute constipation”
No faeces or gas passed
Symptoms of large bowel obstruction developed more quickly true/false
False
develop more gradually due to the large capacity of the colon and caecum and their absorptive activity
In what percentage of large bowel obstruction cases does the ileocaecal valve remain competent
50%
When it is competent it prevents backward flow of bowel contents
If it is incompetent the small bowel distends delaying onset of symptoms
Why does the caecum rupture
Because it is thin walled and progressively distends with swallowed air
‘closed loop obstruction’
What is incomplete obstruction
Bowel only partially obstructed and clinical features less defined
Vomiting intermittent and bowel habits erratic ect.
What causes hypertrophy of the muscle of the bowel wall
chronic incomplete construction
What are some physical signs of intestinal obstruction
Dehydration Abdominal distension Visible peristalsis Relative lack of abdominal tenderness Obstruction abdominal mass may be palpable Resonant percussion due to gas Groin may have obstructing hernia
Bowel obstruction with tenderness
Bowel strangulation
What do bowel sounds sound like in intestinal obstruction
High-pitched and tinkling
What investigations to do for SBO
Abdo x-ray - shows bowel proximal to obstruction distended with gas
CT - confirms diagnosis and look for cause
Where do distended small bowel loops lie on AXR
Central
Where does the distended large bowel sit on AXR
Anatomical position and has haustra coli
What does a CT of a bowel obstruction show
Distended bowel proximal to obstruction and collapsed bowel distal
Initial management of intestinal obstruction
Nil by mouth
Insert IV cannula and send blood
Resuscitate with IV fluids replacing electrolyte losses
Pass a nasogastric tube to decompress the stomach
Mechanical causes of bowel obstruction
Adhesions or bands Incarcerated abdominal wall hernia Internal hernia Volvulus Tumour Inflammatory strictures Bolus obstruction Intussusception
What causes adhesions or bands
congenital
previous abdominal surgery
peritonitis
(they are scarring)
What are incarcerated abdominal wall hernias
inguinal femoral umbilical paraumbilical ventral incisional
What is a volvulus of large or small bowel
Mobile loop of bowel rotates causing an obstruction at its neck
What causes inflammatory strictures which cause obstruction
Crohn’s disease
Diverticular disease
Inflam causing narrowing of the bowel
What kind of bolus can cause obstruction
Food bolus
Impacted faeces
impacted gallstone ileus
trichobezoar (ingestion of hair)
What is intussusception
A segment of bowel wall becomes folds into the segment distant to it
eg. small intestine inside the large intestine and ileocaecal valve
What is bowel strangulation
Segment of bowel becomes trapped so that its lumen becomes obstructed and its blood supply compromised
What is Adynamic bowel obstruction
failure of peristalsis
Risk factors for adynamic bowel obstruction
Recent GI surgery
Inflammation with peritonitis
Diabetic keto acidosis
Types of adynamic bowel obstruction
Paralytic ileus
Pseudo obstruction
Treatment for adynamic bowel obstruction
‘Drip and suck’ while awaiting restoration of peristalsis
What is pseudo obstruction
acute dilation of the colon in the absence of colonic obstruction in acutely unwell patients
