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Chapter 10: Defecatory Dysfunction

Gena Dunivan; William Whitehead

DEFINITION

Defecatory dysfunction is an ill-defined term that encompasses a broad range of symptoms related to infrequent or hard stools and difficult or incomplete evacuation of the rectum. Patients generally lump these together and think of them collectively as symptoms of “constipation;” when healthy young adults were asked what they mean by “constipation,” they referred, in descending order of frequency, to straining, hard stools, “want to but can’t,” infrequent stools, abdominal discomfort, and “haven’t finished.”1 Unfortunately, the symptoms reported by patients are not a reliable guide to the pathophysiologic basis of their symptoms or the choice of optimal treatment. Consequently, the Rome Foundation2 recommended a two-tiered basis for evaluating constipation: Patients are first asked how many of six commonly reported symptoms of constipation they experience at least 25% of the time, and if they endorse two or more of these symptoms and rarely experience diarrhea, they are said to have clinically significant or “functional” constipation (Table 10-1). If patients meet these symptom criteria for functional constipation and fail to respond to a trial of conservative treatment and laxatives, physiologic testing is recommended to further define the pathophysiologic basis of their constipation and to choose an appropriate treatment.

Key Point

  • Defecatory dysfunction encompasses a broad range of symptoms related to infrequent stools and difficult or incomplete evacuation of the rectum.

Table 10-1

Rome III Diagnostic Criteria for Functional Constipation

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Table 10-1

Rome III Diagnostic Criteria for Functional Constipation
Diagnostic criteria*

  1. Must include two or more of the following:

    1. Straining during at least 25% of defecations

    2. Lumpy or hard stools in at least 25% of defecations

    3. Sensation of incomplete evacuation for at least 25% of defecations

    4. Sensation of anorectal obstruction/blockage for at least 25% of defecations

    5. Manual maneuvers to facilitate at least 25% of defecations (eg, digital evacuation, support of the pelvic floor)

    6. Fewer than three defecations per week

  2. Loose stools are rarely present without the use of laxatives

  3. Insufficient criteria for irritable bowel syndrome

*Criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

Reproduced with permission from Ref.10

The main causes of functional constipation can be divided into the four categories listed below. As described later in this chapter, there are different treatment indications for each of these:3

  • Slow transit constipation, in which decreased peristaltic motility in the colon causes a delay in transit throughout the colon

  • Dyssynergic defecation, which is a functional disorder in which the pelvic floor muscles paradoxically contract or fail to relax sufficiently to allow stool passage when the subject strains to defecate

  • Obstructed defecation, which is a structural disorder in which evacuation is impeded by factors such as rectal prolapse, intussusception, enterocele, or rectocele

  • Idiopathic constipation, in which both colonic transit and rectal evacuation are within normal limits and the cause ...

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