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: read more.

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
• pathology
  • 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
• radiologyrole of imaging
  • abdominal radiography is often the first-line investigationconfirm obstruction (XR, CT)
  • CT is a much more useful and sensitive test
    • allows assessment ofdemonstrate cause (CT)
    • illustrate transition point​ (CT)
  • 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

  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)

  The plain film will demonstrate dilated loops of small bowel 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, and have valvulae conniventes that traverse the lumen of the bowel completely and are seen as lines that cross the lumen from wall to wall.

  The level of obstruction can be estimated and the cause may be demonstrated (gas in the femoral canal), but usually a CT is required.

  CT

  CT confirms the diagnosis with dilated loops of gas- or fluid-filled loops of small bowel. The level of obstruction is determined by looking for the calibre change of small bowel and CT allows accurate assessment of the level of obstruction. CT will also usually givehighlight the diagnosisunderlying cause (if a cause is not demonstrated, itbowel obstruction is usually adhesionalsecondary to post-surgical adhesions).​