The stem
An 80-year-old woman with previous abdominal surgery has two days of absolute constipation and a distended, painful abdomen.
Abdominal imagingImages on Radiopaedia
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Case courtesy of Ian Bickle, Radiopaedia.org. View the case. Licensed CC BY-NC-SA 3.0.
The examiner’s questions
Question 1Describe the findings.Show the model answer
Multiple dilated, fluid-filled small bowel loops in the centre of the abdomen, up to 3 cm across, with collapsed large bowel. A transition point in the proximal ileum in the pelvis. A "small bowel faeces" appearance in some pelvic loops. A nasogastric tube lies in a distended, fluid-filled stomach.
Question 2What is the diagnosis and the most likely cause?Show the model answer
Small bowel obstruction. In a patient with previous abdominal surgery and no hernia, the most likely cause is adhesions.
Question 3How do you tell small bowel from large bowel on a plain film?Show the model answer
Small bowel lies centrally and its folds (valvulae conniventes) cross the whole width of the loop. Large bowel lies around the periphery and its haustra do not cross the full width. The 3-6-9 rule: small bowel over 3 cm, colon over 6 cm and caecum over 9 cm are abnormal.
Question 4What is your management?Show the model answer
Nil by mouth, nasogastric tube on free drainage, intravenous fluids with electrolyte replacement, urinary catheter, and regular re-examination. Operation if signs of strangulation develop or the obstruction does not resolve.
After you answerThe teaching pointShow
The "small bowel faeces" sign is seen just proximal to a transition point, where bowel contents stagnate. Look for it when searching for the level of obstruction.
Related: Model clerking: bowel obstruction →
Source case on Radiopaedia: “Adhesional small bowel obstruction”, by Ian Bickle.
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