BSFS SCALEObjective Transit Time Assessment
Visual Characteristics
Gastro-Analytic Engine
Select a stool type to visualize clinical interpretation and standard diagnostic pathways.
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Standardized classification of stool consistency and form
To differentiate between constipation, normal bowel habits, and diarrhea
Initial screening and subtyping of Irritable Bowel Syndrome (IBS-C, IBS-D, IBS-M)
Monitoring response to fiber therapy, laxatives, or anti-diarrheal medications
Surrogate marker for colon transit time in clinical practice
Clinical Context
Stool form is a better indicator of transit time than stool frequency. This scale allows patients to communicate their bowel habits visually, reducing subjective descriptors like "loose" or "hard."
How it Works
The 7 Stool Types
01
Type 1: Separate hard lumps, like nuts (hard to pass).
02
Type 2: Sausage-shaped but lumpy.
03
Type 3: Like a sausage but with cracks on its surface.
04
Type 4: Like a sausage or snake, smooth and soft.
05
Type 5: Soft blobs with clear-cut edges (passed easily).
06
Type 6: Fluffy pieces with ragged edges, a mushy stool.
07
Type 7: Watery, no solid pieces. Entirely liquid.
Transit Time Correlation
| Type 1 | Very Slow Transit (~100 hours) |
| Type 3-4 | Normal Transit (~24–48 hours) |
| Type 7 | Very Fast Transit (< 10 hours) |
Clinical Pearls
IBS Subtyping (Rome IV)
Subtyping is based on bowel habits on days with at least one abnormal bowel movement. Note: This requires the scale to be used over a representative period (e.g., 2 weeks).
IBS Definitions
IBS-C (Constipation): > 25% of stools are Type 1-2; < 25% are Type 6-7.
IBS-D (Diarrhea): > 25% of stools are Type 6-7; < 25% are Type 1-2.
IBS-M (Mixed): > 25% of stools are Type 1-2 AND > 25% are Type 6-7.
Clinical Pearls
Type 4 is often considered the "ideal" stool consistency
Stool consistency is highly dependent on water absorption in the colon; Type 1 reflects excessive water absorption due to slow transit
Bile acid malabsorption typically presents with persistent Type 6-7 stools
Next Steps
Therapeutic Adjustments
01
Type 1–2: Increase soluble fiber and fluid intake; consider osmotic laxatives (PEG).
02
Type 6–7: Screen for malabsorption, infection, or IBD; consider anti-motility agents (Loperamide) if non-inflammatory.
The Evidence
The Original Scale
Stool form scale as a guide to intestinal transit time.
Lewis SJ et al. • Scandinavian Journal of Gastroenterology. 1997;32(9):920-4. The foundational study at the Bristol Royal Infirmary.
View Source• . ;
Clinical Validation Study
Revisiting the Bristol Stool Form Scale: validity and reliability for clinical and research use.
Blake MR et al. • Aliment Pharmacol Ther. 2016;44(7):693-703. Modern validation confirming its utility as a surrogate for transit.
View SourceOrigins & History
The Bristol Royal Infirmary
Developed by Ken Heaton and S.J. Lewis in 1997 at the University of Bristol. It was initially designed to help standardise the description of faeces in clinical research, but has since become the ubiquitous standard in both clinical practice and public health education.
Last Comprehensive Review: 2026-07-17