Causes of fecal incontinence

Anal continence is defined as the ability to retain intestinal content, regardless of its consistency, until the individual considers that it is the right time and place for evacuation. Therefore, fecal incontinence is the leakage of the contents of the rectum to the outside at unexpected times and involuntarily.

At no time is it a condition of aging and its presence is always pathological.

The causes of fecal incontinence can be classified into several types:

• By overflow

In elderly patients or patients with severe and long-standing constipation, the more liquid feces may leak from more proximal sections of the intestine, passing through the hard fecal mass (or fecaloma); then a pseudodiarrhea appears. Fluids are more difficult to contain in the rectum (even under normal conditions), and large fecalomas usually alter the mechanism and pressure play of the rectal wall and sphincters that contribute to continence. For this reason, in these situations incontinence appears to the liquid stools that have overflowed by the fecaloma. This situation is known as fecal impaction.

• Decreased reservoir (colonic, rectal, or both)

The decrease in storage capacity alters the relationship between pressure and volume in the rectum, in such a way that for a certain volume of distension, rectal pressures increase. People with inflammatory bowel disease (ulcerative colitis or Crohn's disease) involving the rectum and distal colon, radiation damage to the colon and rectum, chronic rectal ischemia, and surgery with removal of the colon and ileum junction (part end of the small intestine) to the rectum decrease the stool storage capacity, early awakening the defecation reflex.

• Rectosphincteric alterations

Due to peripheral neurological abnormalities, which affect the sensitivity of the rectal area, the innervation of the muscles that form the internal (involuntary) and external (voluntary) anal sphincters, as well as central ones, in which the defecatory stimulus is not recognized as such and therefore cannot be inhibited in inappropriate situations. Problems such as pelvic floor injuries (postpartum, neoplastic, post radiation, trauma), neoplasia of the sigmoid and rectum, prolapse of the rectum, alterations of the central nervous system (dementias, sequelae of cerebrovascular accident, tumors, demyelinating diseases) or of the nervous system Peripheral (spinal such as multiple sclerosis, tumors, traumatic, ischemic or tumor myelopathies, or peripheral nerves such as lesions of the sacral plexus of traumatic, tumor or metabolic origin) can cause fecal incontinence.

In most cases there may be various mechanisms involved in the presence of fecal incontinence, so it is useful to classify it into minor and major fecal incontinence. The causes and mechanisms mainly involved are:

• Minor fecal incontinence

  • Soiling (soiling underwear): poor hygiene, thrombosed hemorrhoids, other perianal diseases, diarrhea, immobility, dementia and depression.
  • Gas incontinence: common, little medical significance. Avoid flatulent meals and carbonated drinks.
  • Defecatory urge: fluid incontinence. They feel the stool (liquid) in the rectum, but are unable to maintain continence until reaching the bathroom. The most common causes are inflammatory proctocolitis, irritable bowel and severe diarrhea.
  • True liquid stool incontinence: frequent association in the elderly with fecal impaction due to fecalomas, pelvic floor and anal sphincter dysfunction.

• Major fecal incontinence

  • Pelvic floor injury (postsurgical, obstetric, trauma) and anorectal congenital anomalies.
  • Drugs: laxatives and antibiotics.
  • Complete rectal prolapse.
  • Rectal cancer
  • Neurological disorders: central (stroke, dementia), spinal (multiple sclerosis, myelopathies, tumors) and peripheral (neuropathies).
  • Myopathic diseases: dystrophies and polymyositis.
  • Systemic diseases: scleroderma and amyloidosis.