Capsule Endoscopy: Indications
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Direct answer
The small bowel is the one segment standard endoscopes cannot reach, and capsule endoscopy was built for exactly that gap: a swallowed camera that images the entire small intestine painlessly. Its flagship indication is obscure gastrointestinal bleeding — overt or occult — after negative upper and lower endoscopy, followed by suspected small-bowel Crohn's disease beyond the reach of ileocolonoscopy. The one absolute situation it must not enter is a known or suspected stricture, because the capsule can lodge — retention is the complication every examiner asks about.
What you must remember
- Primary indication: obscure GI bleeding or iron-deficiency anaemia after a negative bidirectional workup (upper endoscopy and ileocolonoscopy, ideally repeated once); diagnostic yield is highest in overt obscure bleeding.
- Suspected Crohn's disease: small-bowel disease with negative ileocolonoscopy and non-diagnostic imaging — mucosal detail beyond CT/MR reach, though without biopsy.
- Other indications: small-bowel polyposis surveillance (Peutz-Jeghers), suspected small-bowel tumour, protein-losing enteropathy, and evaluation of NSAID enteropathy.
- Contraindications: known or suspected obstruction or stricture; swallowing disorders; pregnancy remains off-label caution; older "pacemaker" contraindications have relaxed, but check local policy.
- Retention risk: roughly 1–2% in suspected Crohn's, higher when strictures are established; a patency capsule — a dissolvable, same-sized probe — is used first in high-risk patients.
- Limitations: no biopsies, no therapy, blind reading spots and false negatives with blood only in the colon; a positive study still needs device-assisted (double-balloon) enteroscopy or surgery for histology and treatment.
- Complementary tools: MR/CT enterography excludes strictures and masses before capsule use — the sequence examiners expect when Crohn's is suspected.
- Practical: fasting preparation, real-time viewing in some settings, and explicit instructions on returning if the capsule is not passed.
The obscure-bleed pathway
Order the pathway as an examiner would. Step one: secure the premise — a genuine negative workup, meaning quality upper endoscopy (with second look for bleeding, since lesions like a Dieulafoy or Cameron erosion hide) and colonoscopy reaching the caecum with terminal ileal intubation. Step two: stabilise and time the study — capsule endoscopy performs best when done early after a bleed; delay beyond weeks demonstrably lowers yield. Step three: the capsule study itself, reading for angioectasias — the commonest adult finding — small-bowel ulcers, tumours, or a fresh bleed point. Step four: act on the finding — argon plasma coagulation of an angioectasia or biopsy of an ulcer via double-balloon enteroscopy, or surgical referral for a tumour. Step five: if the capsule shows nothing, resist repeating it reflexively; re-examine the colon and consider the rarer mimics. Now the Crohn's variant: before any capsule in a patient with abdominal pain and weight loss, MR or CT enterography comes first — not merely to find disease, but to exclude a stricture, because dropping a capsule into an undetected stenosis converts a diagnostic test into an obstructive emergency. This ordering — endoscopy, imaging for strictures, capsule, then enteroscopy — is the spine of every exam question on the topic.
Retention is the question behind the question
Whenever a capsule stem appears, the examiner's real target is safety: who cannot have it, and what happens if it sticks. Recite the risk honestly — around 1–2% in suspected Crohn's disease, rising with known strictures — and the mitigation: the patency capsule, which is radiopaque, dissolves after roughly 30 hours if it lodges, turning a potential obstruction into a tolerated trial of patency. The second-layer trap is the reflex to call capsule endoscopy "the next step" for any anaemia: if the colonoscopy was incomplete or the upper endoscopy never repeated, the capsule is premature. A third favourite contrasts capsule with device-assisted enteroscopy — the capsule sees everything and touches nothing; the balloon enteroscope reaches a limited distance but can biopsy and treat. Examiners reward the sentence that captures both: capsule first to localise, enteroscopy to intervene.
Frequently asked questions
What is the main indication for capsule endoscopy?
Obscure gastrointestinal bleeding or iron-deficiency anaemia persisting after negative upper endoscopy and colonoscopy — with the best yield in overt obscure bleeding.
Why must strictures be excluded beforehand?
A capsule cannot traverse a stenosis and may lodge, causing obstruction — the patency capsule is used to test patency in high-risk patients such as Crohn's disease.
What is the capsule retention rate in suspected Crohn's disease?
Approximately 1–2% in suspected disease, higher when strictures are established — the reason MR/CT enterography precedes capsule use.
What can capsule endoscopy not do?
It cannot biopsy or treat; any positive finding needs device-assisted enteroscopy or surgery for tissue diagnosis and therapy.
How is a suspected small-bowel Crohn's patient worked up?
Ileocolonoscopy first, then MR or CT enterography to exclude strictures and characterise disease, then capsule endoscopy for mucosal extent, then targeted enteroscopy.