Note: Scores must be assigned AFTER all cleansing maneuvers (suctioning, flushing) are completed.
Segmental Analysis
Provide individual scores for the right, transverse, and left colon segments to calculate the total Boston scale.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Standardized scoring of bowel cleanliness during colonoscopy
To determine the adequacy of mucosal visualization for screening and surveillance
Mandatory reporting metric in many endoscopy quality assurance programs
To guide the recommended interval for the next colonoscopy
Scoring Timeframe
The BBPS is performed AFTER all cleansing maneuvers (suctioning, washing) are completed by the endoscopist. This differs from scales like Aronchick or Ottawa which are often assessed "as encountered."
Section 2
Formula & Logic
Segment Scores (0–3 each)
01
Right Colon: Including the caecum and ascending colon.
02
Transverse Colon: Including the hepatic and splenic flexures.
03
Left Colon: Including the descending colon, sigmoid, and rectum.
Point Definitions
0 Points
Unprepared colon segment with solid stool that cannot be cleared.
1 Point
Portion of mucosa seen; other areas of segment blurred by staining or residual stool.
2 Points
Minor amount of residual staining/liquid stool; mucosa of segment well-seen.
3 Points
Entire mucosa of segment seen perfectly; no residual fluid or staining.
Total Score (0–9)
The total score is the sum of the three segment scores. A score of 9 represents a perfectly clean colon.
Section 3
Pearls/Pitfalls
The "Adequacy" Threshold
A total score of ≥ 6 is widely accepted as the threshold for an "adequate" preparation for colorectal cancer screening. However, there is a critical caveat...
The Segment Rule
Even if the total score is ≥ 6, any single segment score of ≤ 1 renders the entire procedure INADEQUATE for standard surveillance intervals. The right colon score is the most critical for identifying Sessile Serrated Lesions (SSLs).
Clinical Pearls
BBPS scores ≥ 6 are associated with a significant increase in Adenoma Detection Rate (ADR)
The use of split-dose bowel preparation (half given morning-of) is the most effective way to achieve a score of 3 in the right colon
Documenting the BBPS in every report is a marker of high-quality endoscopy practice
Section 4
Next Steps
Surveillance Implications
01
Total ≥ 6 (and all segments ≥ 2): Standard surveillance based on polyp findings (e.g., 10 years if clean).
02
Total < 6 (or any segment ≤ 1): Repeat colonoscopy within 1 year (or sooner depending on clinical suspicion).
Complementary Tools
Aronchick Scale
Adenoma Detection Rate (ADR) Benchmark
Ottawa Bowel Prep Scale
Section 5
Evidence Appraisal
Original Validation
The Boston bowel preparation scale: a valid and reliable instrument for colonoscopy-oriented research.
Lai EJ et al. • Gastrointestinal Endoscopy. 2009;69(3 Pt 2):620-5. The foundational paper establishing the scoring system.
Developed by Dr. Evan Lai and colleagues at Boston University. It was designed to overcome the subjectivity of global scales by forcing the endoscopist to focus on specific segments of the colon after their best efforts at cleaning were completed.
