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SSc Faecal Incontinence — SCE Rheumatology MCQ

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ModerateSystemic SclerosisSSc Faecal IncontinenceSCE Rheumatology

A 45-year-old woman with limited cutaneous systemic sclerosis reports leakage of stool without preceding urgency or awareness. Anorectal manometry shows reduced resting anal pressure but preserved voluntary squeeze pressure. Which mechanism most directly explains her faecal incontinence?

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Correct answer: D — Atrophy and fibrous replacement of internal anal sphincter smooth muscle causing reduced resting tone

The correct answer is D. Resting anal tone is generated predominantly by the smooth-muscle internal anal sphincter. In systemic sclerosis, internal sphincter atrophy and fibrous replacement reduce resting pressure, producing passive leakage without warning. Anorectal neuropathy may also contribute, including impairment of the rectoanal inhibitory reflex and anal sensation, but the physiological pattern given most directly identifies internal sphincter dysfunction. External sphincter or pudendal nerve disease would preferentially reduce voluntary squeeze pressure. Rapid transit and rectal hypersensitivity more often produce urgency, while pelvic-floor dyssynergia causes obstructed defaecation and may lead to overflow rather than primary passive incontinence.

Reference: Suresh N et al. Systemic sclerosis and anorectal dysfunction: The Leeds experience. Journal of Scleroderma and Related Disorders. 2024;9:210-215. https://pubmed.ncbi.nlm.nih.gov/39386265/