Constipation

Definition

Constipation is a term that refers to a disturbance in bowel function resulting in infrequent stools [Page 285](generally fewer than 3 stools per week) or difficulty with defecation. No single definition of chronic constipation exists; however, it is generally described as constipation of more than 12 weeks that does not respond to dietary fiber or simple therapeutic measures. An international working committee developed diagnostic criteria, known as the Rome III criteria, to promote consistency in the diagnosis of chronic constipation.

Based on the Rome III criteria, the diagnosis should be based on the presence of the following for at least 3 months (with symptom onset at least 6 months prior to diagnosis):

• 1.
  They must include 2 or more of the following.

  • Straining during at least 25% of defecations o Lumpy or hard stools in at least 25% of defecations
  • A sensation of incomplete evacuation for at least 25% of defecations
  • A sensation of anorectal obstruction/blockage for at least 25% of defecations
  • Manual maneuvers to facilitate at least 25% of defecations (e.g., digital evacuation, support of the pelvic floor)
  • Fewer than 3 defecations per week
• 2.
  Loose stools are rarely present without the use of laxatives.
• 3.
  There are insufficient criteria for a diagnosis of irritable bowel syndrome.

A review of epidemiological studies found that estimates of the prevalence of constipation in the United States vary from 2% to 28%, most likely because no standard definition of constipation exists.

Causes and Contributing Factors

Constipation generally occurs because the colon absorbs too much water from food moving through the colon. If the colon's muscle contractions are slow, food may move through the colon too slowly, allowing the colon to absorb an excess of water. As a result, stools can become hard and dry.

Idiopathic constipation refers to constipation that is from an unknown cause. Functional constipation can be classified as slow transit, pelvic floor dysfunction, or a combination of both. Decrease in muscle activity in the colon or uncoordinated motor activity causes slow-transit constipation, whereas pelvic floor dysfunction is caused by a weakness of the muscles in the pelvis surrounding the anus and rectum. Anorectal dysfunction, or anismus, is a form of functional constipation caused by abnormalities in the structure of the anus or rectum. This results in an inability to relax the muscles that allow stool to exit.

Those with constipation generally find it painful to have a bowel movement and experience straining, bloating, and the uncomfortable sensation of a full bowel. Most constipation is temporary and not serious. Sometimes, however, constipation can lead to serious complications when left untreated. Examples of such complications include hemorrhoids and anal fissures caused by straining to have a bowel movement. Moreover, this straining effort can cause a small portion of the intestinal lining to be pushed through the anal opening (rectal prolapse), a condition that may require surgical correction. Constipation may result in fecal impaction, wherein the normal movement of the bowel is not sufficient to expel the stool. Fecal impaction may require administration of an enema and/or manual disimpaction.

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