ASCRS Ch03 — Anorectal Physiology

Citation: Suwanabol PA, Regenbogen SE. "Anorectal Physiology." In: Steele SR, et al. (eds.), The ASCRS Textbook of Colon and Rectal Surgery, 4th ed. Springer Nature Switzerland AG; 2022. pp. 41–49 (PDF pp. 57–66 of the combined textbook file). Source file: raw/ASCRS Textbook 4th Ed.pdf (full 1,198-page textbook; cite by page range within the single PDF).

Type: Specialty textbook chapter (reference/background, not primary literature).

Scope

Third chapter of the sequential full-textbook ingest (see ASCRS Ch01 - Anatomy and Embryology for the ingest's scope/plan). Covers innervation of the anus/pelvic floor, normal continence mechanisms (rectal sensation/compliance, anorectal reflexes including the RAIR, internal/external sphincter roles, puborectalis), normal defecation, physiologic testing (manometry, PNTML, balloon insufflation, defecography), and functional anorectal disorders (fecal incontinence, disorders of defecation, anorectal pain, urogynecologic overlap).

Key content

Full synthesis split across two pages rather than summarized twice here: normal physiology went into the new Anorectal Physiology page; disorders (incontinence, dyssynergic defecation, proctalgia) went into the new Fecal Incontinence page. Physiologic-testing content was merged directly into the existing Anorectal Physiology Testing page (adding normal high-pressure-zone length, balloon insufflation as a distinct sensory test, and PNTML's incontinence/prolapse associations) rather than creating a third overlapping page.

Limitations

• Textbook chapter, not primary literature; explicitly defers diagnostic algorithms and management strategies for the disorders it covers to later chapters (Chaps. 55–59, 65 — not yet ingested).
• The chapter itself repeatedly flags anorectal continence physiology as "incompletely understood," and several testing findings (idiopathic outlet dysfunction's manometric anomalies, RAIR changes) as inconsistent across the studies it cites — presented here as-is, not resolved.

Relevance

Third entry in the ASCRS ingest. Creates Anorectal Physiology (the mechanistic counterpart to the existing Sabiston-sourced Anorectal Physiology Testing) and Fecal Incontinence (a genuinely new topic — the wiki previously touched incontinence only within Rectal Prolapse (Procidentia)'s prolapse-specific context). Trims and redirects Colonic Physiology's RAIR paragraph to avoid duplication, and adds a consistency note (not a contradiction) on internal-sphincter resting-tone percentages between Ch. 2 and Ch. 3.