I never have, but it's very common for doctors to examine bowel movements in hospitals, I've had that done many times. Not just samples either. I have an ileostomy, so it's not quite the same, but my last couple of in-patient hospital admissions my doctors collected all my stoma output for weeks and weeks, and they weighed it every time as well, same as they do with urine. With my stoma, I'd just empty it into the cardboard bowls they give you. People without stomas place the bowl under the toilet seat or use a commode, which I was doing with my urine too. Doctors like to see, weigh, measure, test everything.
What you're proposing is a bit different though, but a doctor won't view it as disgusting. What is it that you think the doctor needs to see? Blood?