I had a similar experience. A doctor got annoyed with me because I didn't want the vaccinations she was offering, and questioned my sanity because I told her I have worms. She wanted me to go see mental health and take anti-depressants. When I told her I wasn't depressed, she very coldly said, "AND you need a colonoscopy!" The next time I went for an appointment, I asked her to schedule the colonoscopy, but she didn't. She said the blood test she did confirmed that I have strongyloids, but my eosonophil count was so low, that I didn't need to be treated for them, yet. She said, "EVERYBODY has them." I agree with you that they are probably using a colonoscopy to rule out what is really there, and they can probably calibrate their diagnostic instruments to make sure nothing shows up. In this case, she was threatening to give me a colonoscopy if I didn't let her vaccinate me.