Small Bowel Obstruction
This is a mechanical or functional obstruction of the small bowel, preventing normal
bowel transit, and is a surgical emergency
Epidemiology
Accounts for about 5% of all surgical emergencies.
Causes
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Adhesions
Hernia
Tumour
Intussusception
IBD
Volvulus
Foreign bodies – e.g. a gallstone in gallstone ileus
Pathophysiology
The bowel becomes obstructed for one of the above reasons, and becomes proximally
distended. Initially this can cause increased peristalsis on either side of the
obstruction and so cause diarrhoea. The intraluminal pressure will continue to rise
due to the accumulation of secretions and swallowed air. Increased hydrostatic
pressure in the capillary beds will cause third spacing into the intestinal lumen and
contribute to dehydration. The degree of vomiting will depend on how proximal the
obstruction is.
Presentation
 Pain – usually colicky pain, though if due to strangulation, the
progressive ischaemia may give rise to constant pain
 Nausea
 Vomiting – if there is bilious vomiting, and a shorter history of pain, the
obstruction is more likely to be proximal
 Diarrhoea – an early finding
 Absolute constipation – a later finding
 Fever
 Ask about previous abdominal surgery
 Ask about a history of malignancy elsewhere – primary small bowel
neoplasm is not common
On examination
 Abdominal distension – more pronounced with distal obstruction
 Increased bowel sounds initially – high-pitched tinking BS, and then
later, absent bowel sounds
 Look for hernias; stoma if present
 Check for signs of bowel ischaemia – fever, tachycardia, signs of
peritonitis
Differentials
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SBO
Gastroenteritis
Small bowel ischaemia
Perforation
Pancreatitis
Rule out MI
Investigations
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FBC – raised WCC
U&E
Group and cross-match
PFA – show the valvulae conniventes extending the full width of the
lumen; loops of small bowel central on film
 Erect CXR – air under diaphragm?
 Barium studies may be useful
 CT is useful especially if the diagnosis isn’t clear and to assess the exact
level of the obstruction
Treatment
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NPO
NG
IV Fluids
Antibiotics to cover gram negative and anaerobes
May need an anti-emetic
Analgesia
Adhesive obstructions often resolve without surgery
Surgery may be required