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Capsule endoscopy

  • Investigation

The patient swallows a pill-sized camera that takes pictures of the small bowel as it passes through, and leaves the body naturally.

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What it is

Capsule endoscopy uses a disposable, pill-sized wireless camera that the patient swallows. As peristalsis carries it through the gut, it takes thousands of images and sends them to a recorder worn on the body, usually for most of a day; a trained reader then reviews the recording. Its main use is the small bowel, which standard upper endoscopy and colonoscopy cannot reach: suspected small-bowel bleeding (overt or occult bleeding, or iron-deficiency anaemia, after a normal upper endoscopy and colonoscopy), suspected or known small-bowel Crohn disease, complications of coeliac disease, polyposis syndromes and small-bowel tumours. It is painless and needs no sedation, but it cannot take biopsies, treat a lesion or be steered, and its position is only approximate. A positive finding is therefore followed by device-assisted enteroscopy (balloon or spiral) or surgery to sample or treat it. The key risk is capsule retention, in which the capsule stays behind a stricture; in patients with known or suspected strictures a dissolvable patency capsule or imaging is used first. MRI is avoided until the capsule has left the body.

Indications

  • Suspected small-bowel bleeding: overt bleeding or iron-deficiency anaemia with a normal upper endoscopy and colonoscopy.
  • Suspected small-bowel Crohn disease, or assessing its extent and response when other tests are inconclusive.
  • Coeliac disease that does not respond to diet, or suspected complications.
  • Surveillance in polyposis syndromes and suspected small-bowel tumours.
  • Colon capsule: selected patients who cannot have or did not complete colonoscopy.

Contraindications

  • Known or suspected bowel obstruction, stricture or fistula, unless patency has been shown first.
  • Swallowing disorders or a risk of aspiration: the capsule can be placed endoscopically instead.
  • Pregnancy: generally deferred until after delivery.
  • A planned MRI before the capsule has passed.
  • Implanted cardiac devices: no longer a bar in most units, but follow local policy.

Preparation and what happens

  1. Explain the test, the recorder and the risk of retention, and get consent — retention may need endoscopy or surgery.
  2. Ask about obstructive symptoms, Crohn disease, NSAID use, abdominal radiation and surgery — these raise the risk of retention.
  3. Arrange a patency capsule or imaging if a stricture is possible — it shows whether a capsule can pass safely.
  4. Clear fluids the day before, then fasting overnight; bowel preparation if the unit uses it — a clean small bowel shows more mucosa.
  5. Stop iron tablets for some days before, as the unit advises — iron darkens the contents and hides the mucosa.
  6. On the day: sensors or a belt and the recorder are fitted, and the capsule is swallowed with water — the recorder stores the images.
  7. Clear fluids after a couple of hours and a light meal later, as instructed — early food slows transit and blurs the view.
  8. Keep the recorder on, avoid strong magnetic fields, and return it at the set time — the images are read afterwards.
  9. Watch for passage of the capsule; report pain, vomiting or distension — these may mean the capsule is stuck.

Risks and complications

  • Capsule retention: the capsule stays in the gut for at least two weeks or needs removal; more common with strictures.
  • Incomplete study: the battery ends before the capsule reaches the colon (slow gastric or small-bowel transit).
  • Aspiration of the capsule into the airway: rare, mainly in older patients or those with swallowing problems.
  • Missed lesions: views are lost in fast segments or with poor preparation, and the duodenum and proximal jejunum are seen briefly.
  • False positives: minor erosions and red spots are common and may not explain the bleeding.

Next step

  • Read the report: lesions found, approximate location (time from the pylorus) and whether the study reached the colon.
  • A bleeding source or lesion: refer for device-assisted enteroscopy, from the mouth or the anus according to its position.
  • Normal study with ongoing bleeding: repeat endoscopy, capsule or CT enterography; persistent anaemia needs a specialist review.
  • Capsule not seen to pass and symptoms appear: abdominal radiograph to locate it; call a senior if there are signs of obstruction.
  • Continue iron replacement and recheck the haemoglobin; the cause still needs a diagnosis.

Test yourself

Think of the answer, then tap the question to see it.

What is the main indication for capsule endoscopy?

Suspected small-bowel bleeding, overt or as iron-deficiency anaemia, after a normal upper endoscopy and colonoscopy.

What is the most important complication of capsule endoscopy, and how is it prevented?

Capsule retention behind a stricture; in patients at risk, a patency capsule or imaging confirms the bowel is open before the real capsule.

Why does a positive capsule endoscopy usually lead to another procedure?

The capsule cannot be steered, take biopsies or treat lesions, so device-assisted enteroscopy or surgery is needed to sample or treat the finding.

Which imaging test must be avoided until the capsule has been passed?

MRI, because the capsule contains metal and electronics; if passage is uncertain, an abdominal radiograph checks first.

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Educational content; it does not replace supervised hands-on training, your institution's protocols or a prescriber's order. A procedure is learnt with a teacher and done only once you are trained to do it.

Sources: Capsule Endoscopy (StatPearls (NCBI Bookshelf), 2023).

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Representative model, for educational purposes only.