Why does Crohn's disease cause diarrhoea?

A healthy bowel absorbs water as stool passes through it. In Crohn's disease, inflammation can reduce this absorption and speed bowel movement, leaving less time for stool to firm up. Inflammation may also increase mucus and lead to urgency, cramps or a feeling that the bowel has not fully emptied.

Diarrhoea is a common presentation of Crohn's Disease. It may worsen during a flare, but a sudden change can also be caused by infection, a food-related illness, antibiotics or another medicine. The pattern and accompanying symptoms matter more than one isolated loose stool.

Replace fluids regularly and include drinks or foods that help replace salts if you are losing a lot of liquid. Eat small meals of foods you can tolerate, and follow any individual dietary guidance from your care team. Keep a note of stool frequency, urgency, pain, blood, fever and what you are able to drink.

Do not use anti-diarrhoea medicines without advice from the clinician who manages your Crohn's disease, particularly if there is blood in stool, fever, significant pain or a suspected flare. Your treatment plan may need review rather than symptom suppression alone.

Contact your care team promptly if diarrhoea is new, worsening, wakes you from sleep, or comes with blood, weight loss, increasing pain or fever. Seek urgent care if you cannot keep fluids down, pass very little urine, feel faint or confused, have severe abdominal swelling, or develop severe persistent pain. These may be signs of dehydration or a bowel complication.

Does this pattern suggest active inflammation, infection or a medicine effect? Should I have stool or blood tests? How should I adjust fluids, diet and activity while symptoms are unsettled?