Bowel Obstruction Flashcards
how can bowel obstruction be classified?
cause (mechanical or paralytic)
site of obstruction (small/large bowel)
degree of obstruction (partial/complete/closed - emergency)
progression (simple without ischaemia/strangulated with aschaemia)
most common causes of small bowel obstruction?
adhesions (usually from previous surgery)
incarcerated hernias
other causes of small bowel obstruction?
meckels diverticulum stricture (crohns) malignant tumours gall stone ileus superior mesenteric artery syndrome (compression from outside bowel) foreign body internal hernia
paediatric causes of small bowel obstruction
congenital atresia
intussusception
congenital stricture and bands
meckels
most common causes of large bowel obstruction?
malignant tumours
volvulus
other causes of large bowel obstruction?
adhesions
stricture (eg diverticular, IBD)
faecal impaction
foreign body impaction
paediatric causes of large bowel obstruction?
hirschsprung disease (lack of relaxing nerve impulses in lower rectum so muscles dont relax)
congenital strictures and bands
meconium ileus (first stool doesnt pass and causes obstruction)
rectal atresia
possible resulting problems in bowel obstruction?
dehydration and hypovolaemia hypokalaemia hyponatraemia hypochloremia metabolic alkalosis compression of intestinal arterioles/capillaries, veins and lymphatics causing bowel ischaemia, necrosis, perforation, increased permeability, sepsis, metabolic acidosis and hyperkalaemia
cardinal symptoms of bowel obstruction?
abdo pain
vomiting
constipation
abdo distension
pathophysiology of obstruction?
obstruction > increased fluid and gas proximal to obstruction leads to distension > distension causes increased peristalsis to force contents past obstruction leading to colicky pain > severe vomiting from distension and pain leads to dehydration and electrolyte imbalance > increased pressure on wall causes fluid to enter intestine > decreased BP and hypovolaemic shock as more fluid shifts into intestines > continued pressure on intestinal wall causes oedema and ischaemia of wall and decreased peristalsis > prolonged ischaemia causes increased permeability and necrosis of wall, intestinal bacteria and toxins leak into blood and peritoneal cavity causing peritonitis
abdo pain in small vs large bowel obstruction?
small = colicky, periumbilical large = colicky or constant
vomiting in small vs large bowel obstruction?
small = early, large volume and bilious large = late, initially bilious the progresses to faecal
constipation in small vs large bowel obstruction?
small = late large = early
abdo distension in small vs large bowel obstruction?
small = less significant large = early and significant
what history suggests adhesional bowel obstruction?
previous surgery
recurrent episodes
pain comes and goes
history suggestive of obstructed hernia causing obstruction?
history of a lump consistent with hernia
irreducible hernia
history suggestive of colorectal cancer?
elderly change in bowel habit PR bleeding weight loss FH of bowel cancer previous polyps anaemia palpable mass in abdo or on PR exam
what history is suggestive of bowel ischaemia?
change of character of pain from dull to sharp and more intense
history suggestive of bowel perforation?
generalised sharp pain worse on moving (peritoneal irritation)
very unwell
feverish
features of bowel obstruction on examination?
features of dehydration (tachycardic, hypotensive, dry membranes)
distended abdo
diffuse abdo tenderness
tympanic percussion note (due to gas build up)
increased high pitched, tinkling bowel sounds (early) or absent bowel sounds (late)
collapsed, empty rectum on PR exam
what signs and symptoms indicate onset of complications in bowel obstruction?
change in character of pain (colicky becoming continuous, dull becoming sharp etc)
rebound tenderness
signs of sepsis
how might recurrent vomiting affect lab values?
HCL loss = hypochloraemia, metabolic alkalosis, hyponatraemia, hypokalaemia
can have paradoxical aciduria
how might dehydration affect lab values?
high haematocrit
high lactate
high urea and creatinine (esp if AKI)
signs of bowel strangulation on lab tests?
metabolic acidosis
high lactate
neutrophilic leukocytosis
signs of sepsis on lab tests?
leukocytosis
high CRP
abnormal coagulation
signs of cancer on lab tests?
microcytic anaemia
imaging to look for bowel obstruction?
AXR supports diagnosis and can show level of obstruction
CT abdomen and pelvis
possible findings on AXR in bowel obstruction?
dilation of bowel loops proximal to obstruction and minimal/no air within bowel loops distal to obstruction
features of small bowel on AXR?
central position in abdomen place circulars (lines across whole bowel) should be <3cm (>3cm = dilation)
features of large bowel on AXR?
peripheral position
haustrations (lines that dont go right across bowel)
colon should be <6cm
caecum should be <9cm
what can a CT show in bowel obstruction?
transition point (dilation proximal and collapse distal to obstruction)
signs of bowel ischaemia
pneumoperitoneum indicates bowel perforation
pathology such as cancer and perforations
signs of ischaemia on CT?
unenhanced bowel loops pneumatosis intestinalis (ring of gas in bowel wall - wall compromised and gas producing bacteria get in)
initial management of bowel obstruction?
urgent resuscitation
drip (fluid resuscitation, correct electrolytes)
suck (intestinal decompression, NG tube insertion)
bowel rest
IV analgesics and anti emetics
when is conservative management used for bowel obstruction?
conservative management for 3-5 days if
- likely cause is adhesions
- no signs of ischaemia/necrosis/perforation
- no signs of clinical deterioration
conservative measures for bowel obstruction?
drip and suck
active monitoring
nil by mouth (gradually increase oral intake once symptoms improve and NG output decreases)
specific treatment for obstructing hernia?
can be gently reduced by a senior if there are no signs of strangulation
specific treatment for fecal impaction?
stool evacuation (manual disimpaction, enemas or suppositories, laxatives)
specific treatment for sigmoid volvulus with no signs of strangulation?
rigid or flexible sigmoidoscope detorsion
are prokinetics used in bowel obstruction?
no
they induce peristalsis which increases chance of perforation
what is sometimes considered in adhesional bowel obstruction?
trial of therapeutic contrast meal and follow through
indications for surgical management?
haemodynamic instability despite resuscitation
signs of ischaemia/necrosis
clinical deterioration
persistent partial obstruction (>3-5 days)
closed loop obstruction
surgical procedure used for bowel obstruction?
exploratory laparotomy
- identify and deal with the obstructing agent
if bowel resection is needed (tumour or necrosis)
- anastamosis or stoma (temporary or permanent) are the options
causes of paralytic ileus?
endocrine abnormalities (hypothyroid, porphyria, uraemia)
neuropathy (diabetes, parkinsons, spinal injury)
medications (anticholinergics, opioids, antidepressants)
