Doctor ordered a lab to see if i have an infection in my colon for diarrhea that i have had for three days. what kind of infections are related to the colon that she would be checking for? thanks?

Likely the test was ordered to confirm if the diarrhea is truly due to a colon inflammation because some conditions may cause diarrhea but not due to inflammation of the colon. I wonder what test, blood or stool, was ordered. Infectious colitis or inflammatory bowel disease are a vast territory which can't be explained in a simple way with this limited communication.

Usual tests involve ruling out parasite infections, bacterial through cultures and other specific tests( looking for toxins) for example or viral. Work up is suggested by history and symptoms/exam.