The Bristol stool scale is a medical diagnosis tool used by Doctors to classify the way feces looks into 7 different categories. It is also known by the names, Bristol stool chart and Bristol stool form scale.
It was developed at Bristol Royal Infirmary in 1997 as a clinical assessment tool, but is also used to help with patients who can't speak, so that they can show their doctor if they have a problem with their bowels (a clinical communication aid). It's also used to help diagnose Irritable Bowel Syndrome.