What to Do If You Have Diarrhea After Drinking Oral Contrast Before MRI
If you experience diarrhea three times after drinking oral contrast but before your MRI enterography, you should still proceed with the scan, but inform the MRI technologist immediately—the study may be suboptimal and require repeat imaging, but it can still detect gross abnormalities and may provide clinically useful information. 1
Understanding the Problem
The diarrhea you're experiencing is likely caused by the osmotic effect of the oral contrast agent itself. Common MRI contrast agents include:
- Polyethylene glycol (PEG) - causes osmotic diarrhea by drawing water into the bowel 2, 1
- Mannitol or sorbitol - sugar alcohols that have similar osmotic effects 2
- Water mixed with these agents - typically 900-1,500 mL total volume 1
The irony is that the contrast designed to distend your bowel for optimal imaging is now rapidly transiting through, potentially compromising the very distension needed for diagnosis 1.
Immediate Actions
Inform the MRI staff before entering the scanner that you've had multiple episodes of diarrhea. This is critical because:
- The technologist may adjust the imaging protocol 1
- They can assess whether adequate bowel distension remains 1
- They may need to document suboptimal preparation for the interpreting radiologist 1
What Happens to Image Quality
Your study will likely be diagnostically compromised but not completely worthless:
- Reduced sensitivity: Standard MRI enterography has 77-82% sensitivity with proper preparation, but this drops to 50-86% with inadequate bowel distension 2, 1
- What can still be seen: Gross abnormalities like large masses, significant bowel wall thickening, abscesses, and fistulas may still be detected 1
- What will be missed: Superficial mucosal abnormalities, subtle inflammatory changes, and early disease require adequate distension and will likely not be visualized 2, 1
Clinical Context Matters
The diarrhea itself may be a diagnostic clue:
The American College of Radiology notes that rapid intestinal transit causing diarrhea may indicate underlying active inflammatory bowel disease, which paradoxically makes adequate imaging even more critical for management decisions 1. If you're being evaluated for Crohn's disease or other inflammatory conditions, this symptom is relevant clinical information.
Options Moving Forward
Option 1: Proceed with Current Scan (Recommended)
- Rationale: Even a suboptimal study may detect significant pathology 1
- Advantage: Avoids delay in diagnosis
- Disadvantage: May require repeat examination 1
Option 2: Alternative Imaging Approach
If you consistently cannot tolerate oral contrast:
- Standard MRI abdomen/pelvis without enterography technique can be performed, though with reduced sensitivity (50-86%) for inflammatory changes 2, 1
- MR enteroclysis (nasoduodenal tube placement) provides equivalent diagnostic performance but is invasive and poorly tolerated 2, 1
For Future Examinations
If you need repeat imaging, discuss these strategies with your ordering physician:
- Slower oral contrast administration: Extending intake time beyond the standard 45-60 minutes may improve tolerance 1
- Reduced volume protocols: While 1,000+ mL is optimal, diagnostically acceptable images can be obtained with as little as 450 mL 1
- Anti-motility agents: Though not standard, these could theoretically slow transit (discuss with your physician)
- Alternative imaging: CT enterography uses the same principle but may have different tolerance 2
Critical Caveat
Do not attempt to "hold" the diarrhea or delay bowel movements once in the scanner—this will cause motion artifact and make the images non-diagnostic. If you need to use the restroom during the scan, inform the staff immediately 1.
Bottom Line
Proceed with the scan, communicate clearly with the MRI staff about your symptoms, and recognize that while the study may be suboptimal, it still has diagnostic value and is better than canceling entirely 1. Your ordering physician can determine if repeat imaging with modified preparation is necessary based on the results and your clinical presentation.