Coexistent faecal incontinence and constipation: A cross-sectional study of 4027 adults undergoing specialist assessment.

Background: In contrast to paediatric and geriatric populations, faecal incontinence and constipation in adults are generally considered separate entities. This may be incorrect.

Methods: Cross-sectional study of consecutive patients (18-80 years) referred to a tertiary unit (2004-2016) for investigation of refractory faecal incontinence and/or constipation and meeting Rome IV core criteria (applied post-hoc) for self-reported symptoms. We sought to determine how frequently both diagnoses coexisted, how frequently coexistent diagnoses were recognised by the referring clinician and to evaluate differences in clinical characteristics between patients with single or both diagnoses.

Findings: Study sample consisted of 4,027 patients (3,370 females [83·7%]). According to Rome IV criteria, 807 (20·0%) patients self-reported faecal incontinence in isolation, 1,569 (39·0%) patients had functional constipation in isolation, and 1,651 (41·0%) met criteria for both diagnoses (coexistent symptoms). In contrast, only 331 (8·2%) patients were referred for coexistent symptoms. Of the 1,651 patients with self-reported coexistent symptoms, only 225 (13·6%) were recognised by the referrer i.e. 86·4% were missed. Coexistent symptoms were most often missed in patients referred for faecal incontinence in isolation. In this group of 1,640 patients, 765 (46·7%) had concomitant symptoms of functional constipation. Opioid usage, comorbidities, childhood bowel problems, mixed incontinence symptoms, prolapse symptoms and structural abnormalities on defaecography were associated with reclassification.

Interpretation: Over 40% of adults referred for anorectal physiological investigation had coexistent diagnoses of faecal incontinence and functional constipation, based on validated criteria. This overlap is overlooked by referrers, poorly documented in current literature, and may impact management.