Small bowel obstruction (summary)

Small bowel obstruction (SBO) accounts for 80% of all mechanical intestinal obstruction; the remaining 20% result from large bowel obstruction. It has a mortality rate of 5.5%.

Reference article

This is a summary article for small bowel obstruction. However, we do have a more in-depth reference article: small bowel obstruction.

Summary

• epidemiology ¹
  • 80% of all mechanical bowel obstruction
  • average age: 64 years
  • females comprise 60% of patients
• presentation
  • abdominal distension, nausea and vomiting
  • the level will determine the acuity of presentation
    • high obstruction presents early, possibly with bilious vomiting
    • lower obstruction presents late and may have faeculent vomiting
• pathologypathophysiology
  • may be complete or incomplete
  • causes​
    • adhesional SBO: occurs almost exclusively from prior surgery
    • herniae (often femoral or inguinal, but incisional occur)
    • foreign bodies or other masses, e.g. gallstones
    • rare: small bowel tumours causing intussusception
• radiologyinvestigation
  • CT is the most sensitive imaging modality
• treatment
  • initial treatment is supportive with decompression (NG) and IV fluids
  • in some cases, conservative management fails and surgery is required
• prognosis
  • depends on the cause and whether complications occur
  • mortality of 5.5% where there are complications:
    • ischaemia
    • perforation

Role of imaging

• confirm obstruction
• demonstrate cause
• find the transition point
• identify any complications, e.g. ischaemia or perforation

Radiographic features

There are a number of ways to investigate small bowel obstruction. A plain radiograph has been the traditional tool for initial assessment and while CT has reduced its use, it remains a tool used by many.

Plain radiograph (AXR)

• dilated small bowel loops (providing they are filled with gas)
  • if they are fluid-filled, you will not be able to see them
• small bowel loops
  • tend to be more central than large bowel
  • have valvulae conniventes that traverse the lumen completely
• the cause may be demonstrated, e.g. gas in the femoral canal

CT

• dilated loops of small bowel
  • the dilated bowel may be gas- or fluid-filled
• transition point at the site of obstruction
  • the cause will be at the transition point
  • if no cause is demonstrated, it's likely secondary to adhesions