Key Points
2
Copyright Rome Foundation, Bristol Stool Form Scale developed by Dr Ken Heaton, University of
Bristol, UK.
e Bristol Stool Form Scale (BSFS) is a useful tool to evaluate bowel habit. e BSFS has
been shown to be a reliable surrogate marker for colonic transit.
Figure 1A. Bristol Stool Form Scale
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 an Italian sausage or snake, smooth and so
Type 5
So 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.
Figure 1B. IBS Subtypes and Stool Form
25% of BM is the threshold
for classification
100
75
50
25
0 25 50 75 100
IBS-C IBS-M
IBS-U IBS-D
% BM loose or watery
% BM hard
or lumpy
Types 1 and 6
Types 6 and 7
Types
1 and 2
IBS subtypes should be established according to stool consistency, using the BSFS. IBS
subtyping is more accurate when patients have ≥4 days of abnormal bowel habits per month.
Bowel habit subtypes should be based on BSFS for days with abnormal bowel habits.
