6.7 Obstruction of the Gastrointestinal Tract Flashcards
What are the three categories of causes of bowel obstruction. Provide examples of each
- 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
Describe the progression of small bowel obstructions
- 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
Describe the character of colicky pain. What does it indicate?
- Colicky pain is severe cramping pain
- Comes and goes suddenly in waves, as per regular bowel movements
- Tends to indicate obstruction of a hollow, muscular tube
How does abdo distension/vomiting (+ contents of vomit) change depending on the location of a small bowel obstruction
- 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
What imaging investigations might we perform to assess for small bowel obstruction?
- AXR
- CT abdomen
Where does large bowel obstruction usually occur? Why?
- Occurs more commonly on left side
- At this point, more water has been resorbed, so stool is more solid
Signs/symptoms of small bowel obstruction on Hx/exam
Hx:
- Colicky abdominal pain
- Nausea/vomiting
- Abdominal distension
- Constipation
Exam:
- Tenderness
- Scars (?post-operative), herniae
How do the signs/symptoms of large bowel obstruction differ from those of small bowel obstruction
- Slower onset of symptoms (slower transport of stuff through the colon than SI)
- Less pain
- Less vomiting (farther to the mouth)
What are some common causes of large bowel obstruction?
- Colorectal cancer (always screen)
- Volvulus (twisting)
- Stricture (IBD, ischaemia, diverticulitis)
- Hernia, adhesions
- Faeces
What is post-operative ileus? What other pathologies can cause ileus?
- 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)
Ogilvie’s syndrome is also called… It typically occurs in settings such as…
- Acute colonic pseudo-obstruction
- Occurs in very sick hospitalised patients (trauma, infectoin, dardiac disease etc.), metabolic disturbance, and medications such as anticholinergics (?dementia)
2 causes of toxic megacolon are…
- IBD
- C Diff infection
Paraneoplastic syndromes occur when…
Anti-cancer components of the nervous system attack the body itself
How can bowel obstruction cause infection?
- Bowel perforation 2° to ischaemic necrosis
- Infection and peritonitis
What are 3 questions we might ask if we suspect small bowel obstruction?
- Does vomiting relieve pain? (decompresses)
- Is this a recurrent problem? (can be)
- Any lumps or bumps (?malignancy, hernia)
Small bowel obstruction Ix
- Bloods (EUC [vomiting may deplete electrolytes], CBC/CRP [inflammation]
- Imaging (what are these?)
What are our operative and non-operative measures for treating small bowel obstruction?
Non-Op:
- IV fluids and electrolytes
- NG tube (remove fluid and gas)
- Analgesia
Operative (sepsis, peritonitis):
- Resection and reconnection
What’s the condition we always need to screen for in suspected colonic obstruction?
CRC
Why do we order a lactate blood test in the setting of large intestinal obstruction?
Indicative of ischaemia (anaerobic respiration)
Why might pain be concentrated in the RIF during colonic obstruction? Why aren’t we worried about confusing it with appendicitis?
- 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
Most common management for large bowel obstruction
- Resect pathology
- Stoma
Most common causes of small vs large bowel obstruction
Small: adhesions, hernia
Large: malignancy, diverticular disease, volvulus (twisting)
