How do I prepare for an MRI for Colorectal Cancer

Preparing for an MRI for Colorectal Cancer

I'm glad you're getting prepared—knowing what to expect makes the experience much smoother. Let me walk you through what typically happens and how to get ready.

Why MRI is Important for Your Care

According to the NCCN Guidelines for Rectal Cancer, pelvic MRI is a key imaging test that helps your doctors:

• Determine the exact size and location of your tumor (called T-staging)
• Assess whether cancer has spread to lymph nodes (N-staging)
• Measure the distance between your tumor and the mesorectal fascia (MRF)—a tissue layer that's important for surgical planning
• Evaluate your tumor's relationship to surrounding structures

For colon cancer, NCCN Guidelines recommend chest/abdomen/pelvis CT as the primary imaging, but MRI may be used in specific situations, particularly if you have liver metastases (cancer spread to the liver) that might be treated.

Before Your MRI Appointment

Schedule & Timing:

• Arrive 10-15 minutes early to complete paperwork
• Plan for the appointment to take 30-60 minutes total (the actual scan is usually 20-40 minutes)
• Wear comfortable, loose-fitting clothing

What to Remove/Avoid:

• Remove all metal objects: jewelry, watches, glasses, hearing aids, dentures, hairpins
• Wear clothes without metal zippers, snaps, or underwire bras (or change into a hospital gown)
• Empty your pockets completely
• Remove any body piercings if possible

Medical Devices:

• Tell the technologist if you have any implants (pacemakers, metal plates, stents, tattoos with metallic ink)
• Bring a list of all medications and supplements
• Inform staff of any allergies, especially to contrast dye (gadolinium)

Eating & Drinking:

• For pelvic MRI: You can usually eat and drink normally unless told otherwise
• For abdominal MRI: Your doctor may ask you to fast (not eat) for 4-6 hours before the scan
• Ask your care team about your specific instructions

Bowel Preparation: According to NCCN Guidelines, rectal distension with gel is not a requirement for MRI staging. However, some facilities may use spasmolytic agents (medications that reduce bowel movement) to decrease artifacts (blurry areas) in the images. Your facility will let you know if this applies to you.

During Your MRI

What to Expect:

• You'll lie on a table that slides into a large, tube-shaped machine
• The machine makes loud knocking and buzzing sounds—this is normal
• You'll be given earplugs or headphones
• The technologist can see and hear you through a camera and speaker
• You must stay very still during the scan—movement blurs the images
• The scan involves multiple sequences (different types of images), each lasting a few minutes

If Contrast is Used:

• An IV (intravenous line) may be placed in your arm
• You'll receive gadolinium-based contrast agent (GBCA) to help visualize the tumor and surrounding tissues more clearly
• This is safe for most people, but tell your team about kidney problems or contrast allergies

Managing Anxiety:

• Let the technologist know if you feel claustrophobic
• Some facilities offer open or wide-bore MRI machines
• Ask if you can listen to music during the scan
• Practice deep breathing beforehand

After Your MRI

• You can return to normal activities immediately
• No special precautions needed
• Results typically available within 1-3 business days
• Your doctor will review the images and discuss findings with you

What Your MRI Report Will Include

According to NCCN Guidelines, your radiologist will document:

• Distance from the anal verge (opening of the anus) to your tumor
• Tumor length and T-stage (how deeply it invades the rectal wall)
• N-stage (whether lymph nodes are involved)
• Circumferential resection margin (CRM) distance—how close the tumor is to the outer tissue layer
• Extramural vascular invasion (EMVI) if present—whether cancer has invaded blood vessels outside the main tumor

Questions to Ask Your Care Team

1. Do I need to fast before my MRI, or can I eat normally?
2. Will contrast dye be used, and do I need to know anything special about that?
3. How long will the scan take, and when will I get results?
4. Should I bring someone with me, or can I drive myself home?
5. What happens after the MRI—when will my doctor discuss the results with me?

Key Takeaway

MRI is a safe, non-invasive imaging tool that gives your oncology team detailed information to guide your treatment plan. Proper preparation—removing metal, following fasting instructions, and staying calm—helps ensure clear images and accurate results.

This information is for educational purposes only. Always consult your healthcare team for personalized medical advice and decisions.