Hello and thank you for your question,
There are several key factors that will help you to distinguish between adhesions, infection and Crohn's flare-up.
During a Crohn's flare-up you will start to experience consistently increasing amount of abdominal pain, increased amount of bloody diarrhea and overall not well being.
With infection, there is no increase in diarrhea and no rectal bleeding. However, you will spike a fever, exhibit fever and chills, along with generalized abdominal pain which is not related to exercise or anything that you do. Nothing will make this pain better or worse (actually same applies to Cronh's flare-up but there you will have bloody diarrhea in addition).
Adhesions which are very common following extensive abdominal surgery usually cause pain upon movement, pain is rather sharp. There is no fever, no diarrhea or blood in the stool with adhesions. What happens is a scar tissue attaches itself to your intestine as well as to the abdominal wall and every time there is movement, it will pull on the intestine causing the pain. If pain from adhesions is bad enough, you can have laparascopic surgery during which adhesions are lysed (broken up), this usually improves pain.
I hope you find this information helpful. Please feel free to follow-up with any other questions you might have.
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Best wishes and good luck,