CT (computed tomography) scans are common enough nowadays, as they are frequently used in diagnosing a wide range of health problems. But, there are certain cases in which you should not undertake such a scan, as in the following cases:
If you have an allergy to iodine or contrast media you can perform the test, but avoid the administration of contrast.
The use of oral contrast is contraindicated in cases of suspected perforation of the digestive tract and before performing a digestive endoscopy or surgery that includes the digestive tract.
The use of intravenous contrast is contraindicated if there is a serious kidney or heart disease and in some tumours such as pheochromocytoma or myeloma. It is also contraindicated in cases of some diseases of the thyroid since the iodine that carries the contrast can be harmful to the thyroid.
Pregnancy is a contraindication to the test, with or without contrast.
CT scans during pregnancy and lactation
This type of test should be avoided during pregnancy, especially during the first trimester, due to the risk of radiation to the fetus. Breastfeeding, in general, does not contraindicate the performance of the test, even if intravenous contrast is administered. The amount of contrast that can be excreted by milk is less than 1% of what is administered, and the amount absorbed by the baby through the intestine is less than 1% of what you ingest. Therefore, the amount that can reach the baby is so small that it is not recommended to stop breastfeeding to perform a CT scan with contrast.
However, mothers who are concerned about any risk this may have on their child because of this minimal exposure to the contrast can avoid breastfeeding for 24 hours after the procedure. This is the time it takes to eliminate all the contrast from the mother’s blood. During these 24 hours, the mother can express her milk by means of a pump and discard it. In anticipation of this period in which you will not breastfeed, the mother can take milk before the test and store enough to cover the needs of the child for 24 hours.
Procedure: how a CT scan is performed
The procedure is similar whether you undergo a private scan in London or in any other healthcare facility. The device in which a CT scan is performed, called a tomograph or scanner, has a donut shape and inside it moves a table where the patient lies, usually face up. The table moves inside the hole of the tomograph for a few seconds and then multiple X-rays are taken. Unlike magnetic resonance imaging, this test does not usually cause claustrophobia, because the patient does not remain inside a closed place. There are also no annoying noises heard either.
In general, it is necessary to change your clothes for a hospital gown. If a head CT scan is performed, it is not usually necessary to change clothes. You will be asked to remove all metallic objects as they interfere with the radiographic images.
If contrast is administered orally, a kind of porridge containing barium will be given to drink before the test. If the contrast is given intravenously, a venous line will be taken in the arm and the contrast will be introduced there just before the images are taken.
During the procedure, a technician will be watching you through a glass window from an adjoining room and will instruct you not to move. Sometimes you might be asked not to breathe for a few seconds. At the end of the test, if you have been given contrast, you can be told to wait a few minutes in an adjoining room in case of an allergic reaction.