Cluster Analysis of Fecal Incontinence Symptoms: Associations With Anorectal Physiology and Quality of Life

The contributions of bowel disturbances and anorectal dysfunctions to fecal incontinence (FI) remain unclear. Based on defecatory awareness, the classification into urge vs passive FI overlooks other factors (eg, leakage volume). This study examined relationships among FI characteristics (stooling sensation, volume, consistency), bowel movements (BMs), and anorectal neurophysiology; evaluated their effect on quality of life (QoL); and identified clinical phenotypes.

Patients completed a 2-week bowel diary, questionnaires, and anorectal manometry. BM and FI characteristics were used for cluster analysis.

Over 2 weeks, 268 patients (88% women) had a mean of 28.2 BMs (standard deviation, 15.2) and 19.7 FI episodes (standard deviation, 15.7). Patients >74 years had more frequent FI (P = .01), more solid-FI episodes (P = .008), better FI-QoL scores (P ≤ .02), and lower anorectal pressures (P ≤ .002) than those <58 years. Solid FI was associated with hard (Bristol Stool Form [BSF] 1-2) stools (r = 0.17; P = .006) and normal (BSF 3-4) stools (r = 0.30; P < .001) and inversely with anal resting pressure (r = -0.25; P < .001) and squeeze increment (r = -0.15; P = .02). Loose (BSF 5-7) stools were associated with liquid FI and urge FI (r ≈ 0.3; P < .001). Urge FI was associated with poorer FI-QoL scores (P < .001). Passive FI was associated with the frequency of normal stools (r = 0.16; P = .009) and lower anal resting pressure (r = -0.15; P = .02). Cluster analysis identified 4 distinct phenotypes, 2 characterized by passive and 2 by combined (urge-passive) FI.

FI characteristics were weakly but significantly associated with BMs and anorectal functions. Diary-captured stool and FI patterns identified 4 phenotypes associated with FI-based QoL and anorectal function. This stratification will likely facilitate the management of FI. (ClinicalTrials.gov, Number: NCT03811821).