6.7 Obstruction of the Gastrointestinal Tract

Question 1

What are the three categories of causes of bowel obstruction. Provide examples of each

Answer 1

• Extraluminal: adhesions to other structures, volvulus [which is…], hernia
• Within the intestinal wall: tumour, stricture [e.g. crohn’s], haematoma
• Intraluminal: intussusception, gallstone, foreign bodies

Question 2

Describe the progression of small bowel obstructions

Answer 2

• Initial obstruction
• Distension
• GI wall becomes oedematous and loses absorptive function
• Ischaemia (blockage of blood supply due to swelling, especially in closed loops)
• Ischaemic necrosis, leading to perforation

Question 3

Describe the character of colicky pain. What does it indicate?

Answer 3

• Colicky pain is severe cramping pain
• Comes and goes suddenly in waves, as per regular bowel movements

Question 4

How does abdo distension/vomiting (+ contents of vomit) change depending on the location of a small bowel obstruction

Answer 4

• Higher obstruction makes vomiting more likely, and distension less likely (closer to stomach, easier exit)
• Lower obstruction makes vomiting less likely, and distension more likely
• In lower SI obstruction, vomit may have a more faecal appearance

Question 5

What imaging investigations might we perform to assess for small bowel obstruction?

Answer 5

• AXR
• CT abdomen

Question 6

Where does large bowel obstruction usually occur? Why?

Answer 6

• Occurs more commonly on left side
• At this point, more water has been resorbed, so stool is more solid

Question 7

Signs/symptoms of small bowel obstruction on Hx/exam

Answer 7

Hx:
- Colicky abdominal pain
- Nausea/vomiting
- Abdominal distension
- Constipation

Exam:
- Tenderness
- Scars (?post-operative), herniae

Question 8

How do the signs/symptoms of large bowel obstruction differ from those of small bowel obstruction

Answer 8

• Slower onset of symptoms (slower transport of stuff through the colon than SI)
• Less pain
• Less vomiting (farther to the mouth)

Question 9

What are some common causes of large bowel obstruction?

Answer 9

• Colorectal cancer (always screen)
• Volvulus (twisting)
• Stricture (IBD, ischaemia, diverticulitis)
• Hernia, adhesions
• Faeces

Question 10

What is post-operative ileus? What other pathologies can cause ileus?

Answer 10

• Loss of regular GI motility following surgery (more common after open surgery)
• Caused by inhibitory neural reflexes in response to abdominal inflammation
• Can also be caused by pancreatitis, retroperitoneal bleed, spinal cord injury (all sources of inflammation)

Question 11

Ogilvie’s syndrome is also called… It typically occurs in settings such as…

Answer 11

• Acute colonic pseudo-obstruction
• Occurs in very sick hospitalised patients (trauma, infectoin, dardiac disease etc.), metabolic disturbance, and medications such as anticholinergics (?dementia)

Question 12

2 causes of toxic megacolon are…

Answer 12

• IBD
• C Diff infection

Question 13

Paraneoplastic syndromes occur when…

Answer 13

Anti-cancer components of the nervous system attack the body itself

Question 14

How can bowel obstruction cause infection?

Answer 14

• Bowel perforation 2° to ischaemic necrosis
• Infection and peritonitis

Question 15

What are 3 questions we might ask if we suspect small bowel obstruction?

Answer 15

1. Does vomiting relieve pain? (decompresses)
2. Is this a recurrent problem? (can be)
3. Any lumps or bumps (?malignancy, hernia)

Question 16

Small bowel obstruction Ix

Answer 16

• Bloods (EUC [vomiting may deplete electrolytes], CBC/CRP [inflammation]
• Imaging (what are these?)

Question 17

What are our operative and non-operative measures for treating small bowel obstruction?

Answer 17

Non-Op:
- IV fluids and electrolytes
- NG tube (remove fluid and gas)
- Analgesia

Operative (sepsis, peritonitis):
- Resection and reconnection

Question 18

What’s the condition we always need to screen for in suspected colonic obstruction?

Answer 18

CRC

Question 19

Why do we order a lactate blood test in the setting of large intestinal obstruction?

Answer 19

Indicative of ischaemia (anaerobic respiration)

Question 20

Why might pain be concentrated in the RIF during colonic obstruction? Why aren’t we worried about confusing it with appendicitis?

Answer 20

• Occurs when ileocaecal valve is incompetent; stool piles up, causing pain
• We aren’t worried about confusing it, among other things, because we’ll need to order a CT scan for either

Question 21

Most common management for large bowel obstruction

Answer 21

• Resect pathology
• Stoma

Question 22

Most common causes of small vs large bowel obstruction

Answer 22

Small: adhesions, hernia
Large: malignancy, diverticular disease, volvulus (twisting)