Bristol Stool Chart / Bristol Stool Form Scale

Abstract

The Bristol Stool Form Scale (BSS), also known colloquially as the Meyers Scale in certain regions of England, is a standardized clinical assessment tool designed to classify human feces into seven distinct categories based on consistency and appearance. The scale was developed by gastroenterologists at the University of Bristol, providing a visual reference crucial for evaluating bowel habits and diagnosing various gastrointestinal conditions.

The classification system is highly correlated with the duration the stool spends in the colon, known as intestinal transit time. Stool morphology is influenced by factors such as hydration, diet, and the presence of conditions like constipation or diarrhea. The BSS is frequently used in conjunction with a defecation diary to accurately monitor and address chronic defecation problems in clinical settings.

Keywords

Bristol Stool Form Scale, BSS, Stool Consistency, Fecal Assessment, Gastrointestinal Disorders, Defecation, Bowel Habits, Constipation, Diarrhea, Lewis and Heaton.

Authors

Lewis SJ, Heaton KW (1997)

Purpose

The primary purpose of the Bristol Stool Form Scale (BSS) is to offer a non-invasive, reliable, and standardized method for both patients and clinicians to objectively classify the form and consistency of human feces. This objective classification system is vital for the differential diagnosis and subsequent monitoring of gastrointestinal pathologies, particularly those involving deviations in bowel motility.

By establishing a clear visual correlation between stool type and intestinal transit time, the scale enables healthcare providers to infer the speed of waste passage through the digestive tract. Types 1 and 2 are indicative of slow transit (often linked to constipation), while Types 6 and 7 suggest rapid transit (diarrhea). This standardized visual tool significantly improves consistency in clinical documentation and patient self-reporting.

Construct

The BSS is fundamentally designed to measure the physiological construct of fecal consistency, which serves as a highly reliable proxy for colonic function and the speed of intestinal transit. The scale operates on the principle that the duration of time the fecal matter remains in the large intestine dictates the amount of water reabsorbed; prolonged transit results in harder, drier forms (Types 1–2), whereas rapid transit results in water retention and softer, liquid forms (Types 6–7).

Despite its simplicity, the scale provides a critical observational metric directly related to overall digestive health, making it an indispensable tool for assessing conditions such as Irritable Bowel Syndrome (IBS), chronic functional constipation, and various forms of gastroenteritis. It transforms the often-subjective description of bowel movements into quantifiable, ordinal data points.

Validity

The Bristol Stool Form Scale is recognized for its high face and content validity, as the seven categories comprehensively cover the clinical spectrum of typical and abnormal bowel habits. Its concurrent validity is robust, demonstrated by significant correlations with objective physiological measures of colonic function, including the use of radiological markers to determine actual intestinal transit time.

Furthermore, the scale is globally recognized and endorsed by leading gastroenterologists and major medical associations, underscoring its strong criterion validity as the standard monitoring and diagnostic instrument for functional bowel disorders.

Reliability

The reliability of the BSS is generally excellent, particularly concerning inter-rater reliability among medical professionals. The clear, descriptive, and pictorial definitions provided for each of the seven stool types minimize potential ambiguity, ensuring high consistency in classification across different healthcare providers.

In the context of patient self-reporting, reliability remains high, especially when the scale is utilized consistently, often in combination with a defecation diary. This makes the BSS a highly effective and reliable instrument for longitudinal patient monitoring in both clinical practice and large-scale research studies.

Factor Analysis

As the Bristol Stool Form Scale is an observational, single-item measure designed to categorize a singular physiological continuum (fecal consistency), complex psychometric factor analysis is generally not applicable or necessary. The scale inherently operates on a single dimension: the spectrum of solidity versus fluidity in fecal matter, which is directly governed by the duration of colonic transit.

The seven categories serve as descriptive, ordinal data points along this single factor. The primary clinical utility of the BSS resides in its immediate descriptive power and its established correlation with physiological transit markers, rather than in the measurement of complex underlying latent psychological constructs.

Instrument

Test Type: Clinical Observation / Patient Self-Report Visual Aid

Format: Seven-point pictorial and descriptive scale

Language Available: English (Original), Dutch (Bristol Stoelgangschaal), and numerous other translations globally.

Population Group: Clinical and General Population

Age Group: Adults, Elderly

Population Details: Specifically used for individuals requiring assessment of bowel function, particularly those presenting with symptoms related to defecation disorders, chronic diarrhea, or chronic constipation. The scale is easily understood by the target population.

Test Methodology: The patient visually compares their most recent stool to the seven images/descriptions on the chart and records the corresponding number. Classification is based on the appearance of the stool immediately after defecation.

Keywords

Bowel Motility, Fecal Matter, Stool Classification, Lewis SJ, Heaton KW, Irritable Bowel Syndrome, Gastrointestinal Assessment, Colon Transit.

Authors

Author ORCID Identifier: N/A

Affiliation Email addresses: N/A (Original affiliation: University of Bristol)

Correspondence Address: N/A

Permissions & Fee and Test Year

The Bristol Stool Form Scale is widely considered a public domain tool for standard clinical and non-commercial academic use, owing to its status as a fundamental medical assessment instrument. Formal reproduction for large-scale commercial research may necessitate proper acknowledgment of the authors (Lewis & Heaton) and the University of Bristol. Generally, no specific fee is required for its routine application.

Test Year: 1997

Reference’s

The original PDF for the explanatory form (Toelichtingsformulier) can be downloaded here: https://scales.arabpsychology.com/wp-content/uploads/instrumenten/468_1_N.pdf

The original PDF for the instrument (Meetinstrument) can be downloaded here: https://scales.arabpsychology.com/wp-content/uploads/instrumenten/468_3_N.pdf

Lewis SJ, Heaton KW. Stool form scale as a useful guide to intestinal transit time. Scandinavian Journal of Gastroenterology, 1997; 32(9): 920-924. DOI: 10.3109/00365529709033830.

Items of the Bristol Stoelgangschaal / Bristol Stool Form Scale

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

1. Type 1: Separate hard lumps, like nuts (difficult to pass).
2. Type 2: Sausage-shaped, but lumpy.
3. Type 3: Like a sausage but with cracks on the surface.
4. Type 4: Like a sausage or snake, smooth and soft (Normal).
5. Type 5: Soft blobs with clear-cut edges (passed easily).
6. Type 6: Fluffy pieces with ragged edges, a mushy stool.
7. Type 7: Watery, no solid pieces. Entirely liquid.