Magnetic Resonance Imaging (MRI) is a non-invasive medical procedure that uses strong magnetic fields and radio waves to generate detailed images of internal body structures. Preparation is crucial for patient safety and obtaining diagnostic-quality images. What you are permitted to drink before the scan is not a universal rule but depends entirely on the specific type of MRI being performed. Always follow the specific instructions provided by your imaging center to ensure the best outcome.
When Fasting is Required
The most frequent instruction concerning fluids is fasting, which requires abstaining from drinking anything for a set period. This requirement usually applies to scans involving the administration of intravenous (IV) contrast material, often a Gadolinium-based agent. The fasting period is typically four to six hours prior to the scheduled examination time.
The primary reason for this restriction relates to safety during contrast administration. Some patients experience temporary nausea or vomiting when the contrast is injected. If the stomach is full, the risk of aspiration—breathing stomach contents into the lungs—increases significantly, which can lead to serious complications.
Fasting is also necessary for scans focusing on the abdomen and pelvis, sometimes even without IV contrast. Consuming food or drink stimulates peristalsis, the involuntary muscular contractions of the digestive tract. These movements can cause motion artifacts that blur the images of nearby organs like the liver, pancreas, or kidneys. An empty stomach and bowel minimize this internal motion, allowing the scanner to capture sharper, more detailed pictures, improving diagnostic accuracy.
Specific Oral Preparations for Imaging
In some specialized examinations, the drinking instruction is reversed, requiring the consumption of specific fluids. Magnetic Resonance Enterography (MRE), which images the small bowel, requires the patient to drink a large volume of a specialized liquid contrast agent. This contrast, often a product like VoLumen, is a biphasic agent designed to distend the small intestine.
This liquid contains non-absorbable additives, such as polyethylene glycol or mannitol, which help retain water within the bowel lumen. The goal is to fully expand the collapsed loops of the small bowel. This allows the radiologist to clearly visualize the intestinal wall for assessment of conditions like inflammatory bowel disease. Patients may be asked to consume approximately one liter of this solution over 30 to 45 minutes before the imaging begins.
Magnetic Resonance Cholangiopancreatography (MRCP), which visualizes the bile and pancreatic ducts, sometimes requires a negative oral contrast. This fluid is designed to eliminate or darken the signal from the surrounding gastrointestinal tract. Certain natural substances, such as black tea or pineapple juice, have been studied for their high Manganese content. This acts as a negative contrast to improve visualization of the ducts by eliminating background noise and enhancing the target structures.
Clarification on Water and Medications
When fasting is required, a common concern is whether essential medications can still be taken. Generally, a small sip of plain water is permitted to swallow necessary prescription medications, such as those for blood pressure or heart conditions. This allowance is made because the small volume of water will not significantly affect the stomach’s emptiness or the risk of aspiration.
It is imperative to confirm this with the imaging center, especially regarding certain medications. For example, some diabetes medications, like Metformin, may need to be temporarily paused or adjusted when IV contrast is used due to risks related to kidney function. Blood thinners or insulin may also require specific pre-scan instructions from the ordering physician.
During a required fast, only plain water in minimal amounts is acceptable for medication. Clear liquids such as coffee, tea, fruit juices, or carbonated sodas are not allowed. These drinks can stimulate the digestive system or contain substances that interfere with the scan. Consuming them disrupts the intended physiological state of fasting, potentially leading to a rescheduled appointment.
Overall Preparation Guidelines
Preparation for an MRI extends beyond managing fluids, encompassing essential safety and comfort measures. Since the scanner operates using a powerful magnetic field, all metallic objects must be removed before entering the exam room. This includes jewelry, watches, hairpins, and any clothing containing metal zippers or snaps.
Patients will typically be asked to change into a hospital gown to ensure no hidden metal interferes with the magnetic field or causes burns. It is also necessary to inform the technologist about any internal metallic implants. These include pacemakers, aneurysm clips, or joint replacements, which must be noted on a detailed safety screening form.
In addition to metal safety, arrive on time and communicate any concerns, such as claustrophobia or the possibility of pregnancy. Staff can provide earplugs or headphones to manage the loud operational noises of the machine. Always verify all preparation instructions directly with the imaging facility, as protocols can vary based on the specific equipment and radiologist preference.