65.Bowel obstruction. Classification and pathophysiologic mechanisms.

Question 1

Bowel obstruction - Key Point

Answer 1

Mechanical small bowel obstruction is the most common surgical emergency

Question 2

Bowel obstruction - Classification - Small bowel obstruction

Answer 2

o Paralytic (ileus)

o Mechanical
 Complicated
 Simple
 Complete
 Partial

Question 3

Bowel obstruction - Classification - Intestinal obstruction (prof stoikov’s classification)

Answer 3

o Mechanical
 Obturation
 Intraluminal
 Extraluminal (compressive)
 Intramural
 Strangulation
 Volvulus
 Intussusception
 Adhesive
 b/w bowel loops, SI, LI, other organs. Causes partial obstruction

o Dynamic
 Spastic
 Paralytic

Question 4

Bowel obstruction - Etiology

Answer 4

• Intraluminal – foreign bodies, gall stones, meconium
• Intramural – tumours, crohn’s, strictures
• Extra-luminal – adhesions, hernia’s, carcinomas, abscess, sup mesenteric artery syndrome
• 75% of cases are due to intra-abdominal adhesions from previous abdominal surgery

Question 5

Bowel obstruction - Pathophysiology:

Answer 5

• Early on in the case of obstruction – increased intestinal motility + contractile activity in an attempt to propel contents post obstruction thus increase in peristalsis = diarrhoea
• As obstruction progresses – bowel dilates thus H2O + electrolytes accumulate intraluminally + in bowel wall therefore loss of fluids – dehydration + hypovolemia
  o In case of proximal obstruction loss of fluid = hypovolemia, hypokalaemia, metabolic alkalosis. Shock may occur
• As intraluminal pressure increases in bowel - can lead to decrease in mucosal blood flow therefore if bowel becomes twisted there is increased risk of ischaemia = bowel perforation = peritonitis
• Normally jejunum + proximal ileum are stable but in bowel obstruction = contaminated by E.coli + klebsiella – this can lead to sepsis

Question 6

Bowel obstruction - Clinical Presentation

Answer 6

Colicky Ab pain

N/V

Constipation

Ab. distention

Hyperactive bowel sounds (initially) – later stages = minimal

Question 7

Bowel obstruction - Diagnostic Investigations

Answer 7

• 4 D’s
  o Distinguish mechanical obstruction from ileus

o Determine etiology of obstruction

o Discriminate partial from complete

o Discriminate simple from strangulated

• X-ray
• Contrast radiograph with gastrograffin – establish degree of obstruction
  o NB: in dehydrated pt can exacerbate dehydration. Is hyperosmolar – can stimulate peristalsis
• CT

Question 8

Bowel obstruction - Treatment -

Non Operative

Answer 8

• Fluids + electrolytes replacement (ringer laclate solution)
• Monitor vitals + urine output
• NGT (nasogastric tube) to decrease vomiting + decrease distention + decrease risk of aspiration
• Analgesia

Question 9

Bowel obstruction -

Treatment - Operative

Answer 9

o Generally surgery is mandatory if small bowel obstruction

o If secondary to adhesions – those are cut

o If tumour – bypass

o If crohn’s – tx = conservatively or chronic bowel resection

Question 10

Bowel obstruction - Simple Obstruction

Answer 10

• Simple: mechanical blockage of flow of bowel contents w/o compromising viability of intestinal wall

Question 11

Bowel obstruction - Strangulated Obstruction

Answer 11

• Strangulated: usually involves a closed loop obstruction in which the vascular supply to a segment of intestine is compromised

o Therefore can lead to infarction

o Assoc. with increased morbidity + mortality therefore important to acknowledge signs:

 Increased HR, fever, leucocytosis, constant non-cramping Ab pain