Large Bowel Obstruction

Large bowel obstruction
Typically causes a less severe disease than small bowel obstruction
-          Symptoms are more gradual in onset
-          There are often loud borborygmi (normal bowel sounds)
-          Rectum is usually empty, and the abdomen is non-tender
-          Pain is lower down in the abdomen
-          There may be greater distension than with small bowel obstruction

Large Bowel Obstruction

-          Colon cancer
-          Benign strictures – e.g. diverticular disease, IBD, ischaemic bowel, radiation damage
-          Sigmoid colvolvulus
-          Intersusception
-          Herniae – not as common as in small bowel obstruction
-          Psuedo-obstruction (same as paralytic ileus, except it affects the large bowel)

-          Abdominal distension and absolute constipation
-          Vomiting – a very late sign
-          Patient may have history of history of change in bowel habit and / or rectal bleeding
-          Ask about family history – IBD and colon cancer

Closed loop obstruction
Ileo-caecal valve is competent and as a result fluids and other materials can continue to pass into the large intestine (the bowel produces up to 9L of fluid per days, so even if NBM, intestinal activity cannot be completely suppressed).  Colon distends massively (>12cm – normal <6cm), and the caecum is at risk of rupture and life-threatening faecal peritonitis.
Incompetant IC valve
The obstruction causes the small bowel to distend, and may induce vomiting
Not as urgent as closed loop obstruction, because perforation isn’t as bigger risk
Can be safely imaged with barium enema / endoscopy

Colonic stenting
Can be used in palliative care where surgery isn’t appropriate
Can also be used to buy time – ‘bridge to surgery’. The stent may allow the patient to recover enough to be fit enough for an operation.
Usuually, it is colonic cancer that is stented.
Apple core stricture - a sign of colon cancer – it is a sign on barium enema,where the lumen of the bowel looks a bit like an apple core due to the cancer causing a stricture.

Similar pathogenesis to paralytic ileus
You cant exclude mechanical obstruction without colonic imaging.
Mostly the same causes as paralytic ileus, but can be affected by drug use (e.g. anti-depressants), neurological disease and pneumonia.

Notes by Tom Leach

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