What to do if I have diarrhea three times after ingesting oral contrast before an MRI (Magnetic Resonance Imaging) enterography?

Management of Pre-Scan Diarrhea During MRI Enterography

Immediate Decision

Inform the radiology staff immediately about the diarrhea episodes, as this significantly compromises bowel distension and will likely render the study non-diagnostic, requiring repeat examination. 1

Understanding the Problem

The hyperosmolar oral contrast agents used for MRI enterography (mannitol, PEG, sorbitol) are specifically designed to draw fluid into the bowel lumen to achieve distension. Patients should be warned that they might experience cramping and diarrhea after ingesting these agents - this is an expected side effect mentioned in the ECCO-ESGAR guidelines. 2

However, three episodes of diarrhea before scanning indicates:

• Excessive fluid loss from the bowel lumen, preventing adequate distension 1
• Rapid intestinal transit that may paradoxically indicate active inflammatory bowel disease 1
• Insufficient retention of contrast material needed for diagnostic imaging 2

Clinical Options

Option 1: Proceed with Caution (Suboptimal)

• The study may still detect gross abnormalities but will likely be non-diagnostic for subtle mucosal changes, requiring repeat examination 1
• Diagnostic accuracy depends critically on proper bowel distension - studies performed without adequate distension have inferior diagnostic accuracy 2
• Superficial mucosal abnormalities, bowel wall thickening, hyperenhancement, and mural edema cannot be adequately assessed without proper luminal distension 1
• Penetrating complications including fistulae, abscesses, and sinus tracts require optimal distension for detection 1

Option 2: Consider Anti-Diarrheal Medication (Preferred if Time Permits)

• Loperamide 4 mg (two capsules) initially, followed by 2 mg after each unformed stool, with maximum 16 mg daily 3
• This may slow transit and allow some contrast retention, though timing is critical 3
• Clinical improvement with loperamide is usually observed within 48 hours, which may be too long for immediate imaging needs 3

Option 3: Reschedule with Modified Protocol (Most Definitive)

For patients who consistently experience diarrhea with standard oral contrast, consider these alternatives:

• MR enteroclysis with nasoduodenal tube placement provides equivalent diagnostic performance to standard MRI enterography 1
• However, this is invasive and poorly tolerated in acutely ill patients 1
• Standard MRI abdomen/pelvis without enterography technique can detect Crohn disease, though with reduced sensitivity (50-86%) for subtle inflammatory changes 1

Critical Technical Considerations

• Volumes exceeding 1,000 mL provide superior distension, though diagnostically acceptable images can be obtained with as little as 450 mL 2, 1
• The diagnostic performance of MRI enterography (sensitivity 77-82%, specificity 80-100%) depends critically on proper oral contrast preparation 1
• Studies performed without oral contrast preparation have inferior diagnostic accuracy compared to those performed after administration of oral contrast 2

Practical Algorithm

1. Immediately notify radiology staff - they need to know about inadequate preparation 1
2. If <30 minutes until scan: Proceed but document suboptimal preparation; expect limited diagnostic yield 1
3. If >30 minutes until scan: Consider loperamide 4 mg and attempt additional small volume (200-300 mL) of oral contrast 3
4. If recurrent problem: Schedule MR enteroclysis or accept standard MRI without enterography technique with reduced sensitivity 1

Important Caveats

• The diarrhea itself may indicate underlying active inflammatory bowel disease with rapid intestinal transit, which paradoxically makes adequate imaging even more critical for management decisions 1
• Patients with GFR <60 mL/min/1.73 m² should avoid oral phosphate-containing preparations due to nephropathy risk 1
• Different oral contrast agents (MiraLAX, Breeza, VoLumen) have varying palatability, with MiraLAX showing superior completion rates (70%) compared to VoLumen (30%) 4