Small Bowel Obstruction

Question 1

What is the aetiology of SBO?

Answer 1

Within the lumen

• Gallstones
• Food bolus
• Bezoars
• Parasites (eg Ascaris)
• Enterolith
• Foreign body

Within the wall

• Inflammation (crohns/ radiation enteritis)
• Infection (TB)
• Ischaemia (SMA embolus/ SMV thrombosis)
• Tumour (primary/ secondary)

Outside the wall

• Adhesions (congential/ aquired)
• Hernia (inguinal, femoral, incisional, umbilical, internal)
• Intussusception
• Volvulus

Question 2

What are the symptoms and signs of SBO?

Answer 2

4 cardinal features;

• Vomitting
  
  • Faecalant vomitting (faecal is caused by fistula)
• Colicky central abdo pain
• Constipation (absolute)
• Distension

Question 3

What are the differential diagnoses of SBO?

Answer 3

• Gastric outlet obstruction (eg duodenal ulcer or stomach malignancy)
• Infection conditions
• Ascites, carcinomatosis
• Pancreatitis

Question 4

What is the definition and differences between simple, closed lopp and strangulated obstructed bowel?

Answer 4

Simple

• 1 obstructing point & no vascular compromise
• Closed-loop

2 obstruction points

• Forming loop of grossly distended bowel at risk of perforation

Strangulated

• Compromised blood supply
• Sharper, more constant, localized pain than the central colic of obstruction
• Peritonism is cardinal sign
• Fever, inc. WBC and other signs of mesenteric ischaemia

Question 5

What is an ileus? And what is the difference between an ileus and mechanical obstruction?

Answer 5

Ilius is the loss of GI motility.

• Only refers to loss of peristalisis (not obstruction generally)

Differenes between ilius and obstruction;

• Ilius has no pain
• Ilius has absent bowel sound

Question 6

What investigations would you perform in suspected SBO?

Answer 6

• Ealier vomiting
• Less distension
• More pain
• AXR
  
  • Central gas shadows with valvulae conniventes (cross the lumen)
  • Consider gallstone ileus - calcified gallstone & possible air in biliary tree (confirm by USS)
• FBC
• U&E
• LFTs/ amylase/ CRP
• Clotting studies
• Arterial blood gases (metabolic acidosis may indicate bowel ischaemia)
• CT
  
  • Useful in malignant LBO as also identifies metastases
• Contrast radiology

Question 7

Outline the management of SMO

Answer 7

• Drip & suck (IV fluids & NGT)
• Analgesia
• Oxygen
• Stop motility stimulants & ensure alternative routes for any medications
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