Select leakage frequencies per type to visualize severity index.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Objective quantification of fecal incontinence severity from the patient's perspective
Selecting candidates for surgical or procedural intervention (e.g., Sacral Nerve Stimulation)
Monitoring therapeutic success in pelvic floor physical therapy and biofeedback
Standardized reporting in colorectal and urogynecology research
Clinical Objective
The FISI is a weighted index that accounts for the type of leakage (gas, mucus, liquid, or solid stool) and its frequency. It was designed to reflect "patient/surgeon weighted" priorities rather than simple frequency counts.
Section 2
Formula & Logic
The 4 Leakage Categories
01
Gas: Incontinence to flatus.
02
Mucus: Discharge/seepage of mucus.
03
Liquid Stool: Uncontrolled passage of loose feces.
04
Solid Stool: Uncontrolled passage of formed feces.
Frequency Weighting
Patients rate frequency from Never (0) to ≥ 2 times per day. The score is calculated using a predefined matrix of weights (Total 0–61). Higher scores indicate greater severity.
Severity Matrix (Simplified)
Solid Stool (Daily)
Highest Weight (e.g., 20+ pts)
Gas (Monthly)
Lowest Weight
Section 3
Pearls/Pitfalls
Patient vs. Surgeon weighting
The FISI is unique because it was developed using two sets of weights — one from patients and one from surgeons. Interestingly, patients often rate "liquid stool" leakage as more distressing than surgeons do. The standard FISI typically presents the "Surgeon-Weighted" score as the default metric.
FISI vs. Wexner (Cleveland Clinic) Score
The Wexner score is simpler and also includes "social disruption" and "pad use" which the FISI does not. However, the FISI is considered more granular for research assessing changes in specific "types" of incontinence.
Clinical Pearls
Solid stool incontinence (even weekly) should trigger a search for major structural defects (e.g., large sphincter tear or rectal prolapse)
Liquid stool incontinence is commonly associated with "overflow" in the setting of chronic constipation/impaction (encopresis)
A 10-point drop in FISI is generally associated with reaching a "Patient-Acceptable Symptom State" (PASS)
Section 4
Next Steps
Management Decisions
01
High FISI (Solid/Liquid): Referral for Anorectal Manometry (ARM) and Endoanal Ultrasound.
02
Persistent Moderate FISI: Trial of loperamide, fiber optimization, and biofeedback therapy.
Complementary Scoring
Wexner Incontinence Score
FIQL (Fecal Incontinence Quality of Life)
Anorectal Manometry (ARM) Interpreter
Section 5
Evidence Appraisal
The Foundational Paper
Patient and surgeon ranking of the severity of symptoms associated with fecal incontinence: the fecal incontinence severity index.
Rockwood TH et al. • Diseases of the Colon & Rectum. 1999;42(12):1525-32. The primary description and weighting study.
Developed by the American Society of Colon and Rectal Surgeons (ASCRS) research group. The goal was to remove the ambiguity of previous binary outcome measures (Incontinent: Yes/No) and acknowledge that incontinence exists on a complex multidimensional spectrum.
