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Chapter: Medicine Study Notes : Gastro-Intestinal

Bowel Obstruction

High small bowel: mainly vomiting, less distension/pain, no constipation, more rapid onset

Bowel Obstruction




·        High small bowel:  mainly vomiting, less distension/pain, no constipation, more rapid onset

·        Low large bowel: mainly distension/constipation/pain, evolves over days/week („sub-acute‟)

·        Visceral pain Þ poorly localised to either epigastric, peri-umbilical or subrapubic regions




·        Small vs. Large

·        Complete vs. Incomplete

·        Open loop vs. closed loop

o   Open loop: mainly colicky pain – comes in waves.  Either top end or bottom end still open

o   Closed loop: 

§  Isolated loop ® ­peristalsis & ­fluid ® ­intramural pressure ® ¯capillary perfusion & compromised venous drainage ® gangrene ® perforation (rapidly fatal through sepsis and mass cytokine release)

§  Symptoms: quick (6 hours start to finish), constant severe pain that started colicky, ­temperature & ­pulse once infarction starts

§  X-rays & WBCs may be normal

§  Differential diagnosis pancreatitis (do amylase)




·        Intraluminal: e.g. 

o   Choleocystoduodenal fistula ® gallstone ileus. Gallstone moves from gallbladder to duodenum via fistula (® air into bilary tree). Also following ERCP 

o   Bezoar: lump of stuff (e.g. hair) intermittently blocking ileocaecal valve

·        In the bowel wall:

o   Crohn‟s

o   Tb

o   Tumours of small bowel. (Less common) – lymphoma, carcinoid (neuro-endocrine), adenocarcinoma, melanoma secondaries

·        Outside wall 

o   Hernia of small bowel, especially indirect inguinal or femoral (Þ always examine groin)

o   Adhesion from previous surgery (Þ look for scars): can take years to present acutely 

o   Small bowel volvulus: malrotation of embryonic mesentery (can also be acquired, e.g. drugs) ® easy rotation of mesentery 

o   Intussusception: piece of bowel forced into distal section. Rare, most common in kids (2 months ® 2 years). Especially around ileocaecal valve

·        Also in large bowel:

o   Diverticular stricture and cancer (most common in sigmoid)

o   Volvulus: of any part of colon (especially sigmoid) 

o   Distal obstruction can also cause ileocaecal valve to shut ® close loop obstruction. Caecum ischaemic first as biggest radius (Law of La Place) 

o   Pseudo-obstruction: motility problem (esp. after recent surgery). Check with barium enema, contrast will go through OK but rectum will be empty




·        History: bowel movements, previous surgery, weight loss

·        Exam: dehydration (from vomiting) & distension

·        Treatment:

o   Rehydration: crystalloid (i.e. saline) – only want to restore ECF (i.e. not dextrose)

o   Nasogastric tube: suck out stomach contents ® ¯vomiting & aspiration

o   Urinary catheter: monitor fluids 

o   Monitor creatinine: if hypoperfusion ® kidney failure

·        FBC: group & save 

·        Pain relief: 10 mg im morphine or slow infusion. If dose is bad enough to need another then need surgery 

·        If no scars & no hernias ® surgery

·        If scars ® may settle (if operate ® more adhesions).  Regular review


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