Obstructed defecation (also known as rectal outlet obstruction, evacuatory dysfunction, obstructed defecation syndrome, outlet constipation, and pelvic outlet obstruction), is "difficulty in evacuation or emptying the rectum [which] may occur even with frequent visits to the toilet and even with passing soft motions". The conditions that can create the symptom are sometimes grouped together as defecation disorders. The symptom tenesmus is a closely related topic.
Another source defines evacuatory dysfunction as "a constellation of symptoms such as prolonged repeated straining at bowel movements, sensation of incomplete evacuation, and the need for digital manipulation".
Some describe an "obstructed defecation syndrome", defining it loosely as "difficulty in evacuation, which may or may not be associated with constipation"
- incomplete or unsuccessful attempts to evacuate,
- prolonged episodes on the toilet,
- rectal pain,
- digitations or perineal massage to aid defecation
- enema dependency
Fecal incontinence to gas, liquid, solid stool, or mucus in the presence of obstructed defecation symptoms may indicate occult rectal prolapse (i.e. rectal intussusception), anal sphincter dysfunction, or descending perineum syndrome.
Obstructed defecation is one of the causes of chronic constipation. Obstructed defecation could be considered to be a type of bowel obstruction, where it may be classified under large bowel obstruction. Obstructed defecation frequently gives rise to a symptom called tenesmus. Constipation, bowel obstruction and tenesmus are therefore all closely related topics.
Outlet obstruction can be classified into 4 groups.
- Functional outlet obstruction
- Inefficient inhibition of the internal anal sphincter
- Inefficient relaxation of the striated pelvic floor muscles
- Mechanical outlet obstruction
- Dissipation of force vector
- Impaired rectal sensitivity
- Rectal hyposensitivity
The two key features of obstructed defecation are:
A 5 item questionnaire was validated for diagnosis and grading of obstructed defecation syndrome. The parameters were:
- Excessive straining
- Incomplete rectal evacuation
- Use of enemas and/or laxatives
- Vaginal-anal-perineal digitations (needing to press in the back wall of the vagina or on the perineum to aid defecation)
- Abdominal discomfort and/or pain
Obstructed defecation may be a cause of incomplete evacuation of stool. Normal emptying of rectal contents is 90-100%. <90% evacuation could be defined as incomplete evacuation. Incomplete evacuation is also one of the factors implicated in the cause of fecal leakage.
One review stated that the most common causes of disruption to the defecation cycle are associated with pregnancy and childbirth, gynaecological descent or neurogenic disturbances of the brain-bowel axis. Patients with obstructed defecation appear to have impaired pelvic floor function.
Specific causes include:
- Anismus and pelvic floor dysfunction
- "Rectal invagination" (likely refers to rectal intussusception)
- Internal anal sphincter hypertonia
- Anal stenosis
- Fecal impaction
- Rectal or anal cancer
- Descending perineum syndrome
Obstructed defecation has many causes, so the management in any individual case is specific to the cause of the symptom.
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- Wexner, edited by Andrew P. Zbar, Steven D. (2010). Coloproctology. New York: Springer. p. 140.
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