Bowel Obstruction Flashcards
How much fluid is excreted by ____ in a day? What is its pH?
a. saliva
b. stomach
c. brunner’s glands
d. pancreas
e. bile
f. SI
g. LI
a. 1000ml pH 6.0-7.0
b. 1500ml pH 1.0-3.0
c. 200ml pH 8.0-9.0
d. 1000-1500ml pH 8.0-8.3
e. 1000ml pH 7.8
f. 1800ml pH 7.5-8.0
g. 200ml pH 7.5-8.0
How is fluid lost in bowel obstruction?
obstruction –> distention –> nervous impulses –> emesis –> fluid loss
occlusion –> gross distension of proximal bowel –> increased peristalsis secretions of electrolyte-rich fluids into the bowel lumen
What is mechanical bowel obstruction?
something physical blocking bowel lumen
What is adynamic bowel obstruction?
eg adynamic ileus
= failure of passage of enteric contents through small bowel and colon that are not mechanically obstructed
= paralysis of intestinal motility
What can cause adynamic ileus?
drugs eg opioids metabolic eg hyponatraemia sepsis trauma or surgery MI/CHF head injury peritonitis retroperitoneal haematoma
How is bowel obstruction diagnosed?
generalised uniform gaseous distension of large/small bowel on radiograph
may have a localised sentinal loop
What is the difference between simple and complex obstruction?
Simple = no evidence of risk of perforation
Complex = bowel looks ischaemic or perforated - may occur in closed loops or necrotic bowel
What is a closed-loop obstruction?
two points along the course of bowel are obstructed
usually due to adhesions
in large bowel = volvulus
What is pseudo-obstruction?
= clinical features of SBO w/o any mechanical cause
often painless distension + constipation
consider medication, electrolytes and long-term immobility
What portion of all bowel obstructions does SBO make up?
around 80%
What are the cardinal features of SBO?
pain
distension
vomiting
absolute constipation - no faeces no flatus - after a while
How can you diagnose SBO on CT?
dilated SB loops >25-30nm from outer walls
distal normal/collapsed bowel
SB faeces sign (black dots in SB as faeces form due to excess water reabsorption)
may see; ischaemia perforation mesenteric oedema (due to strangulation) pneumatosis
List some common causes of SBO?
Extra luminal:
adhesions
hernia
volvulus
Luminal:
gallstone
intussusception
polyps
Luminal wall:
inflammatory - Crohn’s
malignancy
infarction
When is surgery indicated for a patient with SBO?
if it’s complete/complicated/strangulated
if it’s partial and conservative management hasn’t worked for the last 48-72hrs
What surgery is performed for SBO and how?
emergency laparotomy + fluid resus pre-operative prophylactic abx nasogastric decompression analgesia correct underlying cause
midline incision
division of adhesions and identify the transition point
milk proximal bowel through NG tube
SB resection if ischaemic - primary anastomoses with sutures/staples
examine the whole length of bowel
How would you treat a complex SBO if surgery is contraindicated?
nasogastric decompression IV fluid resus analgesia anti-emetics antispasmodics
How do you treat partial SBO?
IV Fluid resus - Ringer's lactate/normal saline nasogastric decompression correct underlying cause analgesia - morphine sulphate Foley catheter to measure UO anti-emetic
if poor response 48-72 hrs later –> surgery
What biochemical changes occur as a result of SBO?
dehydration
vomiting
hypokalaemia + alkalosis
strangulation –> inflammatory markers
How can XR be used to determine the extent of SBO?
CXR - to check for pneumoperitoneum
AXR
Partial - gas throughout abdomen + into rectum
Complete - no distal gas + staggered fluid-air levels
Complicated - free air under diaphragm + thumb-printing on bowel (ischaemia)
What complications can arise as a result of SBO?
intestinal necrosis --> perforation sepsis multi-organ failure abscesses short-bowel syndrome
What are the complications post SBO surgery?
Immediate - pain, bleeding, need for stoma, anaesthesia
Early - anastomotic leak, wound breakdown, infection, DVT/PE
Late - adhesions, recurrent obstruction, scars, hernias, stoma complications
What are the 4 main functions of the large bowel?
transit
storage
absorption - vitamins created by colonic bacteria eg K, thiamine and riboflavin
secretion - K+, Cl-
What biochemical changes would you see in LBO?
low plasma volume
electrolyte imbalance
lactate (if ischaemic)
low HCT (if bleed)
What clinical signs would you see in a patient with LBO?
distension quiet bowel sounds hyper-resonant abdomen tender + guarding fever peritonitis hernias (L-sided inguinal associated with sigmoid)
What are the cardinal signs of LBO?
distension
absolute constipation
pain
vominting later
What are the most common causes of LBO?
neoplasm - 90% malignancy structure - diverticular/ischaemic/inflammatory - 3% volvulus - 5% intussusception impaction or obstipation
How is LBO managed?
first-line = supportive treatment
if perforation is suspected or impending –> emergency surgery
Which surgical procedure would you use to treat ___?
a. caecal volvulus/colorectal malignancy/diverticular disease
b. endometriosis
c. pelvic abscess
d. foreign body
a. laparotomy
b. resection
c. percutaneous or transrectal drainage –> resection
d. transluminal removal or laparotomy
What are the potential post-LBO operation complications?
bleeding incisional hernia damage to nearby organs scar tissue wound dehiscence aka wound tearing skin irritation
How can you classify LBO?
Pathology:
dynamic - peristalsis against mechanical obstruction
adynamic - absence of peristalsis w/o obstruction
Anatomy:
SBO - high or low
LBO
Presentation: acute chronic acute on chronic subacute
Pathological changes:
simple = blood supply intact
complicated = blood supply interfered
How can XR be used to diagnose LBO?
CXR - perforation
AXR - colonic dilatation
>9cm for caecum
>6cm for colon
can also visualise volvulus:
colon - coffee-bean shape
sigmoid - dilated inverted U shape
caecal - dilated R colon rotates to L side
