A SeHCAT (pronounced 'see cat') scan looks at how well your body absorbs bile salts.
Bile salt is produced in the liver and stored in the gallbladder. It helps to digest fats and get rid of toxins in the body.
If bile salts are not being absorbed properly, they interfere with how the bowel absorbs water and can cause diarrhoea. This is called bile acid malabsorption (BAM).
You might be referred for this test if you've had recurring diarrhoea for a long time.
The scan will measure the amount of radioactivity in your body after you've swallowed a capsule. The capsule contains a chemical like bile salt, and a small amount of radioactive tracer.
This helps us to diagnose and treat BAM. If you're diagnosed with BAM, we can improve your symptoms dramatically with simple treatment.
Preparing for a SeHCAT study
You can eat and drink normally on the day of the study.
Please contact us if you:
- are taking medicines
- are pregnant, or think you might be
- are breastfeeding
Please contact the nuclear medicine department urgently if you are taking the following medicines or any others for diarrhoea:
It's very important to tell us about any medicines that you're taking. This is because some medicines will need to be stopped before the study as they interfere with the test results. We may not be able to do the study if you have not told us about your medicines.
If you're pregnant or breastfeeding
Radiation can be harmful for an unborn baby. If you are pregnant, or think you might be, you must tell us as soon as possible, ideally before confirming your appointment.
For all nuclear medicine studies we will check your pregnancy status with you before using any radioactive tracer.
Radioactive tracers can be passed into breast milk. Please tell us before you come for your test if you are breastfeeding, and we can tell you if you will need to stop for any amount of time.
A SeHCAT scan
You'll have 2 appointments in the nuclear medicine department, a week apart.
You are welcome to bring a friend or relative with you if needed but space in the waiting area is limited. When you are called for your study, your friend or relative will be asked to wait for you in our waiting area until your study is complete.
Please do not bring children with you, as the area is not suitable for them because of the tests we do in the department.
When you arrive for your appointment, you are given a capsule to swallow. This contains a synthetic bile salt with a small amount of radioactive tracer called selenium. A radioactive tracer has a very small amount of a type of radiation similar to X-ray (known as ionising radiation).
After you take the capsule you'll need to wait for 3 to 4 hours.
You then have a scan to measure the amount of radioactivity in your body. You can leave the department until it's time for your scan. If you prefer, you can sit in our waiting room.
We use a scanner called a gamma camera. You will be asked to lie down and stay as still as possible on a scanning couch. There is no need to undress, but we ask you to remove any metal objects from your clothing or pockets such as coins, belts, watches, and jewellery. Metallic objects can block the camera detecting radioactivity.
The gamma camera will not come close to you and will not touch you. A member of staff is with you at all times. We take a set of pictures and analyse them using a computer programme to measure the radioactivity.
After this, the nuclear medicine technologist or radiographer will ask you to wait for a few minutes while they check the images from your scan are saved on the computer correctly. They will let you know when you can leave the department.
One week later, you will return to the department for the second part of the SeHCAT study. This happens in exactly the same way as the first time but without you needing to swallow a capsule. This means, you will not need to wait 3 to 4 hours again.
The staff cannot give you the result of the SeHCAT study on the day. They will send the results to the doctor who referred you within 2 to 3 working days of the study being completed.
Risks of having a SeHCAT study
You receive a small radiation dose (0.3 millisieverts) from the radioactivity in the capsule when having a SeHCAT study. The amount of radiation is about the same as you would get from natural sources of radiation in about 2 months.
The risks from the radiation are minimal and there are no obvious side effects from taking this capsule, so the benefits of having the test outweigh the risk.
You should not feel sick or drowsy after swallowing the capsule or in the week afterwards, and it will not affect your ability to drive a car. The radiation dose to other people around you is very low, and you do not need to keep away from anyone if you are having this test. Please see above for risks if you are pregnant or breastfeeding.
Giving your permission (consent)
We want to involve you in decisions about your care and treatment. If you decide to have the procedure, we will asked for your verbal (spoken) consent. This proves that you understand what is involved and agree to have the procedure.
Read more about our consent process.
What happens after the study
As soon as the study is completed a member of staff will tell you when you can leave the hospital. It should be very soon after the scan. After the study you can eat and drink as normal.
After the study, the nuclear medicine consultant will send a report to the doctor who referred you for the study. You should already have an appointment booked with the team who referred you. If not, please contact them to arrange a follow-up appointment to discuss the results of the study and any treatment you may need.