Hello! I am sorry your sister is ill but she is lucky to have you to support her. Sadly, my colonoscopy showed cancer 100% so there was no worry about a mis-diagnosis. I was in the far more common situation where I had anal bleeding and my general practitioner said it was hemorrhoids and six months later…

Do you know if they saw any polyps or inflammation? The good news is there was no cancer, but you will have to work with a gastroenterologist to identify the cause- it is possible she has IBS, Chron’s, or something else. Please keep following up until you get answers- the unknown is scary when you know something is not right.