Gastroenterology

Gastroenterology

Volume 126, Supplement 1, January 2004, Pages S14-S22
Gastroenterology

State of the art: pathophysiology
Pathophysiology of adult fecal incontinence

https://doi.org/10.1053/j.gastro.2003.10.013Get rights and content

Abstract

Fecal incontinence occurs when the normal anatomy or physiology that maintains the structure and function of the anorectal unit is disrupted. Incontinence usually results from the interplay of multiple pathogenic mechanisms and is rarely attributable to a single factor. The internal anal sphincter (IAS) provides most of the resting anal pressure and is reinforced during voluntary squeeze by the external anal sphincter (EAS), the anal mucosal folds, and the anal endovascular cushions. Disruption or weakness of the EAS can cause urge-related or diarrhea-associated fecal incontinence. Damage to the endovascular cushions may produce a poor anal “seal” and an impaired anorectal sampling reflex. The ability of the rectum to perceive the presence of stool leads to the rectoanal contractile reflex response, an essential mechanism for maintaining continence. Pudendal neuropathy can diminish rectal sensation and lead to excessive accumulation of stool, causing fecal impaction, mega-rectum, and fecal overflow. The puborectalis muscle plays an integral role in maintaining the anorectal angle. Its nerve supply is independent of the sphincter, and its precise role in maintaining continence needs to be defined. Obstetric trauma, the most common cause of anal sphincter disruption, may involve the EAS, the IAS, and the pudendal nerves, singly or in combination. It remains unclear why most women who sustain obstetric injury in their 20s or 30s typically do not present with fecal incontinence until their 50s. There is a strong need for prospective, long-term studies of sphincter function in nulliparous and multiparous women.

Section snippets

Structure and function of the anorectum

The rectum is a hollow muscular tube, 12 to 15 cm long, composed of a continuous layer of longitudinal muscle that interlaces with the underlying circular muscle.2 The anus is a muscular tube 2 to 4 cm long. At rest, it forms an angle of approximately 90 degrees with the axis of the rectum. During voluntary squeeze the angle becomes more acute, whereas during defecation, the angle becomes more obtuse (Figure 1).

Anorectal sensation

An intact sensation not only provides a warning of imminent defecation, but also helps to discriminate between formed stool, liquid feces, or flatus. Elderly persons,100 physically and mentally challenged individuals, and children with fecal incontinence101 often show blunted rectal sensation. Impaired rectal sensation may lead to excessive accumulation of stool, causing fecal impaction, mega-rectum (extreme dilation of the rectum), and fecal overflow.100, 101 Causes of impaired sensation

Miscellaneous

A variety of medical conditions and disabilities may predispose to fecal incontinence, particularly in the elderly. Immobility and lack of access to toileting facilities are primary causes of fecal incontinence in this population.107 Several medications may inhibit sphincter tone—for example, anticholinergics, some of which are used to treat urinary incontinence and detrusor muscle instability, include tolterodine tartarate (Detrol), Pharmacia, Kalamazoo, MI; oxybutynin (Ditropan), Alza

References (107)

  • C.J. Vaizey et al.

    Primary degeneration of the internal anal sphincter as a cause of passive fecal incontinence

    Lancet

    (1997)
  • A.K. Sood et al.

    Anorectal dysfunction after surgical treatment for cervical cancer

    J Am Coll Surg

    (2002)
  • J.P. Percy et al.

    Electrophysiological study of motor nerve supply of pelvic floor

    Lancet

    (1981)
  • E.T.C. Milligan et al.

    Surgical anatomy of the anal canal with special reference to anorectal fistulae

    Lancet

    (1934)
  • X. Fernandez-Fraga et al.

    Significance of pelvic floor muscles in anal continence

    Gastroenterology

    (2002)
  • B.J. Caruana et al.

    Anorectal sensory and motor function in neurogenic fecal incontinence. Comparison between multiple sclerosis and diabetes mellitus

    Gastroenterology

    (1991)
  • S. Glickman et al.

    Bowel dysfunction in spinal-cord-injury patients

    Lancet

    (1996)
  • N.W. Read et al.

    Anorectal function in elderly patients with fecal impaction

    Gastroenterology

    (1985)
  • S.S.C. Rao et al.

    How useful are manometric tests of anorectal function in the management of defecation disorders?

    Am J Gastroenterol

    (1997)
  • S.S.C. Rao

    Fecal incontinence

    Clin Perspect Gastroenterol

    (1999)
  • K.E. Matzel et al.

    Neuroanatomy of the striated muscular anal continence mechanism. Implications for the use of neurostimulation

    Dis Colon Rectum

    (1990)
  • S. Salmons et al.

    The influence of activity on some contractile characteristics of mammalian fast and slow muscles

    J Physiol

    (1969)
  • R. Kerremans

    Electrical activity and motility of the internal anal sphincter

    Acta Gastroenterol Belg

    (1968)
  • W.J. Wankling et al.

    Basal electrical activity in the anal canal in man

    Gut

    (1968)
  • B. Frenckner et al.

    Influence of pudendal block on the function of the anal sphincter

    Gut

    (1975)
  • C.P. Gibbons et al.

    An analysis of anal sphincter pressure and anal compliance in normal subjects

    Int J Colorectal Dis

    (1986)
  • A.G. Parks et al.

    The syndrome of descending perineum

    Proc R Soc Med

    (1966)
  • B. Gunterberg et al.

    Anorectal function after major resections of the sacrum with bilateral or unilateral sacrifice of sacral nerves

    Br J Surg

    (1976)
  • H.L. Duthie et al.

    Sensory nerve-endings and sensation in the anal region of man

    Br J Surg

    (1960)
  • J.C. Goligher et al.

    The sensibility of colon and rectum

    Lancet

    (1951)
  • M.G. Read et al.

    Role of anorectal sensation in preserving continence

    Gut

    (1982)
  • S.S.C. Rao et al.

    Can biofeedback therapy improves anorectal function in fecal incontinence?

    Am J Gastroenterol

    (1996)
  • A. Wald et al.

    Anorectal sensorimotor dysfunction in fecal incontinence and diabetes mellitus

    N Engl J Med

    (1984)
  • S. Mohanty et al.

    Behavioral therapy for rectal hypersensitivity

    Am J Gastroenterol

    (2001)
  • L. Collet et al.

    Cerebral evoked potentials after endorectal mechanical stimulation in humans

    Am J Physiol

    (1988)
  • J. Rogers

    Anal and rectal sensation

  • A.E. Bharucha et al.

    Viscoelastic properties of the human colon

    Am J Physiol Gastrointest Liver Physiol

    (2001)
  • B. Frenckner

    Function of the anal sphincters in spinal man

    Gut

    (1975)
  • H.L. Duthie et al.

    The relation of sensation in the anal canal to the functional anal sphinctera possible factor in anal continence

    Gut

    (1963)
  • R. Miller et al.

    Anorectal samplinga comparison of normal and incontinent patients

    Br J Surg

    (1988)
  • H. Martelli et al.

    Some parameters of large bowel motility in normal man

    Gastroenterology

    (1978)
  • W.M. Sun et al.

    The role of transient internal sphincter relaxation in fecal incontinence

    Int J Colorectal Dis

    (1990)
  • I.G. Finlay et al.

    A comparison of intrarectal function of gas and mass on anorectal angle and anal canal pressure

    Br J Surg

    (1986)
  • R.C. Garry

    Responses to stimulation of caudal end of large bowel in cat

    J Physiol (Lond)

    (1933)
  • E.A. Gaston

    The physiology of fecal continence

    Surg Gynecol Obstet

    (1948)
  • D. Kumar et al.

    Prolonged anorectal manometry and external anal sphincter electromyography in ambulant human subjects

    Dig Dis Sci

    (1990)
  • H.L. Duthie et al.

    Contribution of the external anal sphincter to the pressure zone in the anal canal

    Gut

    (1965)
  • B. Dubrovsky

    Effects of rectal distention on the sphincter ani externus and levator ani muscles in cats

    Am J Physiol

    (1988)
  • B. Lestar et al.

    The internal anal sphincter cannot close the anal canal completely

    Int J Colorectal Dis

    (1992)
  • B. Lestar et al.

    The composition of anal basal pressure. An in vivo and in vitro study in man

    Int J Colorectal Dis

    (1989)
  • Cited by (0)

    View full text