A contrast agent that shows up the gut on X-rays and CT scans
Barium sulfate
A contrast agent swallowed or given as an enema to make the gut show up clearly on X-rays and CT scans.
What is Barium sulfate?
Barium sulfate is a contrast agent used in imaging, not a medicine that treats an illness. It is swallowed as a drink, or given into the back passage as an enema, so that the inside of the gut shows up clearly on X-rays and CT scans. It works because barium blocks X-rays, coating and outlining the gut so doctors can see its shape and lining. The most important safety point is that it must not be used if a hole or tear in the bowel (perforation) is suspected, because leaking barium can cause serious problems. It can cause constipation and, in some people, carries a risk of being breathed into the lungs.
Education and reference only. This is a plain-language guide to Barium sulfate — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Barium sulfate is a contrast agent, a substance used during imaging to help certain parts of the body show up clearly. It is not a treatment and does not act on any disease; instead, it is a diagnostic aid. For imaging of the gut, it is either swallowed as a chalky drink or given into the back passage as an enema, so the inside of the stomach, bowel or rest of the digestive tract is outlined on X-rays or CT scans. It is given in the imaging department under the supervision of trained staff.
How it works
Barium is a heavy substance that X-rays cannot easily pass through, so anything coated with it shows up brightly on an X-ray or CT scan. When barium sulfate is swallowed or given as an enema, it coats and fills the inside of the gut, outlining its shape, lining and any narrowing, pouches or other changes. This lets doctors see structures that would otherwise be hard to make out on a plain scan. It stays in the gut and is passed out in the stool afterwards rather than being absorbed into the body.
Company & origin
Originated / developed by: Specialist manufacturers.
A contrast agent used in UK imaging departments to outline the gut on X-rays and CT scans; it is a diagnostic aid, not a treatment.
Practical use
How to take Barium sulfate
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it exactly as the imaging staff direct, either drinking it or having it given as an enema.
- Tell the staff beforehand if you have, or might have, a hole or tear in the bowel, as it must not be used then.
- Mention any swallowing difficulties, as there is a risk of it going into the lungs.
- Drink plenty of fluids after the scan to help avoid constipation, unless told otherwise.
- Do not be alarmed if your stools look pale for a day or two as the barium passes out.
Weighing it up
Advantages & disadvantages of Barium sulfate
Advantages
- Makes the gut show up clearly on X-rays and CT scans, helping diagnosis.
- Stays in the gut and is passed out naturally rather than absorbed into the body.
- A long-established and well-understood contrast agent for imaging the digestive tract.
Disadvantages
- It is a diagnostic aid only and does not treat any condition.
- Must not be used if a bowel perforation is suspected, as leaking barium can cause serious harm.
- Can cause constipation or a stool blockage, and carries a risk of being breathed into the lungs in some people.
Practical use
Good to know
It helps to remember that barium sulfate is a diagnostic tool, not a treatment: it makes the gut visible on scans but does nothing to cure or ease a condition. The single most important safety point is that it must not be used when a hole or tear in the bowel (a perforation) is suspected, because barium leaking out of the gut can cause serious inflammation; in those situations a different, water-based contrast is used instead. Because barium stays in the gut, it can cause constipation and, occasionally, a hard blockage of stool, so drinking plenty of fluids afterwards is usually advised. In people who have difficulty swallowing safely, there is a risk of accidentally breathing some into the lungs, so staff take care with how it is given. The staff in the imaging department will explain what to expect, including that stools may look pale for a day or two afterwards.
Who should not take it / use with caution
- People with a known or suspected hole or tear in the bowel (perforation) should not be given it, as leaking barium can cause serious harm.
- It is used with great care, or avoided, in people who have difficulty swallowing safely, because of the risk of it going into the lungs.
- It is used with caution in people with a bowel blockage or severe constipation, under the imaging team's judgement.
Monitoring
- Checking before use that there is no suspected bowel perforation.
- Watching for swallowing difficulties and the risk of it going into the lungs.
- Making sure the bowels open afterwards, especially in people prone to constipation.
Side effects
- Constipation, which is common, and rarely a hard blockage of stool if fluids are not taken.
- Pale-coloured stools for a day or two as the barium passes out, which is harmless.
- Tummy cramps or bloating; rarely, problems if it is breathed into the lungs or leaks through a bowel tear.
Key interactions
- It can interfere with other scans or tests for a short time, so the order of investigations may be planned.
- It is given in place of, not alongside, water-based contrast when a perforation is suspected.
- Tell staff about all your medicines, although barium sulfate has few direct medicine interactions.
Available as: A liquid or paste swallowed as a drink, or a preparation given into the back passage as an enema.
Answers
Barium sulfate: frequently asked questions
What is barium sulfate used for?
It is a contrast agent used during X-rays and CT scans to make the inside of the gut show up clearly; it helps with diagnosis and does not treat any illness.
How is it given?
It is either swallowed as a chalky drink or given into the back passage as an enema, depending on which part of the gut needs to be seen.
When can it not be used?
It must not be used if a hole or tear in the bowel is suspected, because leaking barium can cause serious inflammation; a water-based contrast is used instead.
Will it make me constipated?
It can cause constipation because it stays in the gut, so drinking plenty of fluids afterwards is usually advised to help it pass out.
Why are my stools pale afterwards?
The barium passes out in the stool, which can make it look pale for a day or two; this is harmless and settles on its own.
Authoritative sources
- BNF
- NICE CKS
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