Can You Eat Before an MRI? Not in These 5 Cases

Full-body MRI scans are becoming more popular for preventive health and disease diagnosis due to being non-invasive and radiation-free¹. However, many people haven't had an MRI scan before and are not entirely sure how to prepare for one. This article will look into one of the most common questions from people preparing for an MRI scan: Can I eat before an MRI?

In most circumstances, you can eat and drink as normal before an MRI scan². However, in some circumstances, you will be required to fast. It is essential to follow the preparation guidelines provided by your healthcare professional, as these will advise you on what to do in your specific circumstances.

This article will explain what types of MRI scans require fasting and why these MRI scans require fasting. It will also detail other dos and don’ts in preparing for an MRI scan.

Importance of Checking with Your Physician

Eating before an MRI is usually allowed for standard MRI scans, which don’t use contrast or are not focused on areas surrounding the gastrointestinal tract². Although the majority of MRI scans do not require fasting before a scan, advice may differ depending on the procedures at a particular hospital or imaging centre. As a result, it is always essential to confirm specific pre-scan instructions with the doctor or another healthcare professional, as they will be able to advise you specifically on what you should do.

Five Cases When Fasting Before an MRI is Necessary

MRI with Contrast Agents

Approximately 25 per cent of MRI scans are performed using contrast agents³. Contrast agents are used in MRIs to increase the visual differences between tissues and fluids in the body. The increase in contrast enhances the quality of the images, thus allowing more accurate diagnoses. Contrast agents are commonly used in areas such as soft tissue, abnormal tissue, blood vessels, and specific organs. 

For example, gadolinium-based contrast agents are commonly used in cardiac imaging as they allow the imaging of a myocardial infarction⁴. Contrast agents are administered by injecting into a vein in the hand or arm through an intravenous (IV) line⁵. The injection of contrast agents can cause nausea and vomiting, which can be particularly dangerous when lying down (as in an MRI scanner) due to the risk of airway blockage⁶. Fasting is therefore recommended before an MRI with contrast agents to reduce the risk of vomiting and ensure clear imaging.

Abdominal or Pelvic MRI

Eating or drinking triggers processes in the body to digest what has just been ingested. This involves peristalsis - involuntary muscle contractions throughout the digestive tract to move the food through the digestive system⁷. These muscle movements can cause smearing or anomalies in the MRI image (known as artefacts)⁸. Artefacts may decrease the quality of the MRI image and could obscure any disease-associated anomalies or tumours in surrounding tissues. 

To prevent this from happening, people undergoing abdominal or pelvic MRIs must fast before the scan, as this will decrease the muscle movements of peristalsis, giving a clearer image. MRI scans focusing on areas such as the liver or pancreas will require fasting as these organs are located adjacent to the digestive tract and, therefore, experience peristalsis-related artefacts, decreasing image quality⁹.

Magnetic Resonance Cholangiopancreatography

Magnetic resonance cholangiopancreatography (MRCP) is a specialised form of MRI imaging that is used to visualise the bile ducts and the pancreas. Patients must fast before this procedure to¹⁰:

• Reduce artefacts caused by peristalsis.
• Reduce fluid secretions in the stomach or duodenum, which could interfere with the imaging.
• Promote gallbladder distension - during fasting, the gallbladder fills with bile and stretches¹¹. This makes it easier to visualise the gallbladder and identify any anomalies.

MRI for Gastrointestinal Symptoms

MRIs can be used to investigate digestive symptoms, such as identifying and locating gastrointestinal bleeding or suspected obstructions^12,13. Fasting before these MRI scans is essential, as an empty GI tract and minimised peristalsis are key for good visualisation of bleeding or blockages.

MRI Guided Biopsy or Other Invasive Procedures

MRI is a non-invasive procedure used for imaging; however, it can be combined with invasive procedures to provide real-time imaging and guidance. For example, MRI can be used to guide surgeons when fitting a heart catheter, and MRI-guided biopsies can be carried out to precisely locate abnormal tissue for sampling^12,14. 

These procedures may require a general anaesthetic. Patients must fast before undergoing a general anaesthetic to reduce the risk of vomiting - vomiting can be dangerous when under anaesthesia as the stomach contents can be inhaled into the lungs¹⁵.

Preparing for an MRI Scan: Dos and Don’ts

MRI scans are radiation-free, non-invasive procedures and, as such, are nothing to worry about¹⁶. However, there are certain ways that you can prepare for an MRI and certain things to avoid¹⁷. Medical professionals will advise you on these before you undergo your scan.

Dos:

• Stay hydrated with water in the run-up to the scan (unless advised otherwise) as you won’t be able to consume anything during the scan.
• Dress comfortably in loose-fitting clothing that does not have any metal components (such as zippers, buttons, or underwire).
• Remove all metal objects from your person (such as piercings, jewellery, watches, dentures, and hearing aids).
• Inform your medical professionals of any metal implants or devices within your body - they will be able to assess whether these are MRI-compatible.

Don’ts:

• Avoid wearing makeup or personal care products, such as deodorant, as these can contain ingredients that can interfere with the image quality or that may heat up in the scanner, causing minor burns¹⁸.
• Don’t keep any credit cards or other cards with magnetic strips in your pockets; the magnetic field in the MRI scanner will wipe your cards.
• Don’t eat fatty or greasy foods, particularly before abdominal scans, as these foods can take longer to digest than other foods and, therefore, have the potential to interfere with the image quality.
• Don’t drink excessive amounts of water - remember that you may have to be in the scanner for 60-90 minutes and won’t be able to visit the restroom.

What to Expect if Fasting is Required for Your MRI

Medical professionals will inform you whether you must fast prior to your MRI scan. If fasting is necessary, then you will be required to fast for up to 4 hours before the scan (this may change depending on what is being scanned and differing procedures at different hospitals)¹⁷. If you struggle with managing hunger, it may be wise to schedule an early appointment, if possible, to limit how long you will have to go without food once awake. MRI staff can provide personalised advice and will address any concerns that you may have.

Summary: Can You Eat Before an MRI?

Although many MRI scans will be able to proceed without any prior fasting, a sub-selection of scans will require fasting before undergoing the scan. Scans requiring fasting may include those using a contrast agent, abdominal and pelvic scans, magnetic resonance cholangiopancreatography, gastrointestinal scans, and any scans requiring general anaesthesia. 

These scans require fasting for a variety of reasons, including reducing the risk of vomiting and preventing digestive movements (peristalsis) from interfering with images and reducing their quality. In addition to fasting (if required), there are other ways to prepare for an MRI scan, such as removing all metal items from your person, staying hydrated, and ensuring that you aren’t wearing any personal care products that could interfere with the image quality.

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References

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