The Bristol stool scale or Bristol stool chart is a medical aid designed to classify the form of human faeces into seven categories. Sometimes referred to in the UK as the "Meyers scale", it was developed by Dr. Ken Heaton at the University of Bristol and was first published in the Scandinavian Journal of Gastroenterology in 1997. The authors of that paper concluded that the form of the stool is a useful surrogate measure of colon transit time. That conclusion has since been challenged as having limited validity, and only in types 1 and 2 when the subject is not constipated. However, it remains in use as a research tool to evaluate the effectiveness of treatments for various diseases of the bowel, as well as a clinical communication aid.
The seven types of stool are:
Type 1: Separate hard lumps, like nuts (hard to pass)
Type 2: Sausage-shaped, but lumpy
Type 3: Like a sausage but with cracks on its surface
Type 4: Like a sausage or snake, smooth and soft
Type 5: Soft blobs with clear cut edges (passed easily)
Type 6: Fluffy pieces with ragged edges, a mushy stool
Type 7: Watery, no solid pieces. Entirely liquid
Types 1–2 indicate constipation, with 3 and 4 being the ideal stools (especially the latter), as they are easy to defecate while not containing any excess liquid, and 5, 6 and 7 tending towards diarrhoea.
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