What Causes Small Bruise On Upper Abdomen?

I had a colonoscopy three days ago - all went well. yesterday, I noticed a small bruise develop on my upper abdomen -- above my stomach it seems to be getting larger adn runs from side to side, not up and down, and not a rounded bruise. I understand there could be some bruising with the colonoscopy, but this seems to be an odd place for a bruise, as I figured my colon was below my stomach -- I'm not really concerned, just curious -

By the way, I'm a 54 year old woman.