Diarrhea After MRE Contrast: What to Do
Experiencing diarrhea after drinking MRE contrast is a common and expected side effect that does not require intervention—the osmotic contrast agents (mannitol, polyethylene glycol, or sorbitol) are designed to draw fluid into the bowel for distension, which naturally causes loose stools or diarrhea in many patients. 1
Why This Happens
- Osmotic contrast agents used for MRE (typically mannitol, PEG, or sorbitol solutions in volumes of 900-1,500 mL) work by pulling water into the small bowel lumen to achieve optimal distension 1
- This mechanism inherently causes osmotic diarrhea as a direct pharmacologic effect, not a complication 2
- Studies show that 88% of patients receiving 6.7% mannitol and 44% receiving 3.3% mannitol experience at least one gastrointestinal side effect, with diarrhea being the most common 2
What You Should Know
- Having diarrhea 4 times after drinking the contrast does not compromise your MRE study quality—the contrast has already served its purpose of distending your bowel during the imaging acquisition 1, 2
- The diarrhea typically resolves within several hours as the osmotic agent is eliminated from your system 2
- No specific treatment is needed beyond maintaining adequate hydration if you feel dehydrated from the diarrhea 2
When to Be Concerned
While diarrhea itself is expected, contact your healthcare provider if you experience:
- Severe abdominal pain beyond mild cramping
- Persistent vomiting that prevents fluid intake 2
- Signs of dehydration (dizziness, decreased urination, extreme thirst)
- Bloody diarrhea (this would be unrelated to the contrast itself)
Important Context About MRE Preparation
- The large volume of oral contrast (900-1,500 mL) is necessary to achieve diagnostic-quality bowel distension, though volumes as low as 450 mL can still provide adequate images 1
- Lower concentration mannitol (3.3%) produces similar bowel distension to higher concentrations (6.7%) but with significantly fewer side effects—only 44% vs 88% of patients experience adverse effects 2
- If you need repeat MRE studies in the future, discuss with your ordering physician whether a lower concentration contrast agent might be appropriate, as this maintains diagnostic quality while improving tolerability 2
Bottom Line
Your diarrhea is an expected physiologic response to the osmotic contrast agent and does not indicate a problem with your examination or your health. 2 The imaging study you completed should provide your physician with the diagnostic information needed regardless of the post-procedure diarrhea you experienced. Stay hydrated and the symptoms should resolve on their own within hours.