Anismus
Encyclopedia
Anismus is a malfunction (a focal dystonia
Focal dystonia
Focal dystonia is a neurological condition that affects a muscle or group of muscles in a part of the body and causes an involuntary muscular contraction or twisting...

) of the external anal sphincter and puborectalis muscle
Puborectalis muscle
The fibers which form a sling for the rectum are named the Puborectalis or Sphincter recti.They arise from the lower part of the pubic symphysis, and from the superior fascia of the urogenital diaphragm....

 during defecation
Defecation
Defecation is the final act of digestion by which organisms eliminate solid, semisolid or liquid waste material from the digestive tract via the anus. Waves of muscular contraction known as peristalsis in the walls of the colon move fecal matter through the digestive tract towards the rectum...

. Normal defecation
Defecation
Defecation is the final act of digestion by which organisms eliminate solid, semisolid or liquid waste material from the digestive tract via the anus. Waves of muscular contraction known as peristalsis in the walls of the colon move fecal matter through the digestive tract towards the rectum...

 involves relaxation of both of these muscles. Malfunction involves their failure to relax or their paradoxical increased contraction
Contraction
Contraction may refer to:In physiology:* Muscle contraction, one that occurs when a muscle fiber lengthens or shortens** Uterine contraction, contraction of the uterus, such as during childbirth* Contraction, a stage in wound healing...

. Anismus is a form of functional obstructed defecation and can cause constipation
Constipation
Constipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...

 and painful defecation. It is more common in women than in men, and sometimes is associated with sexual abuse
Sexual abuse
Sexual abuse, also referred to as molestation, is the forcing of undesired sexual behavior by one person upon another. When that force is immediate, of short duration, or infrequent, it is called sexual assault. The offender is referred to as a sexual abuser or molester...

.

Paradoxical contraction of the anal sphincter is fairly common and in many people it does not cause anismus.

Diagnosis

Physical examination can rule out anismus (by identifying another cause) but is not sufficient to diagnose anismus. Anismus needs to be distinguished from rectal inertia, another cause of obstructed defecation and constipation. Techniques proposed to do this include the rectal cooling test. Other techniques include manometry
Manometry
Manometry refers to the evaluation of pressure .Forms include:* Esophageal motility study* Anorectal manometry* Rhinomanometry...

, balloon expulsion test, evacuation proctography (see defecating proctogram
Defecating proctogram
The defecating proctogram or defecography is an imaging study performed by a radiologist in which the mechanics of a patient's defecation are visualized in real time using a fluoroscope.-History:...

), and MRI defecography. Diagnostic criteria are: fulfillment of criteria for functional constipation
Functional constipation
Functional constipation, known as chronic idiopathic constipation , is constipation that does not have a physical or physiological cause. It may have a neurological, psychological or psychosomatic cause...

, manometric and/or EMG and/or radiological evidence (2 out of 3), evidence of adequate expulsion force, and evidence of incomplete evacuation. Recent dynamic imaging studies have shown that in persons diagnosed with anismus the anorectal angle during attempted defecation
Defecation
Defecation is the final act of digestion by which organisms eliminate solid, semisolid or liquid waste material from the digestive tract via the anus. Waves of muscular contraction known as peristalsis in the walls of the colon move fecal matter through the digestive tract towards the rectum...

 is abnormal, and this is due to abnormal (paradoxical) movement of the puborectalis muscle
Puborectalis muscle
The fibers which form a sling for the rectum are named the Puborectalis or Sphincter recti.They arise from the lower part of the pubic symphysis, and from the superior fascia of the urogenital diaphragm....

.

Anismus can be classified by type:
  • Type I: paradoxical anal contraction
  • Type II: impaired propulsion
  • Type III: impaired anal relaxation with adequate propulsion

Complications

Complications
Complication (medicine)
Complication, in medicine, is an unfavorable evolution of a disease, a health condition or a medical treatment. The disease can become worse in its severity or show a higher number of signs, symptoms or new pathological changes, become widespread throughout the body or affect other organ systems. A...

 of anismus may include fecal impaction
Fecal impaction
A fecal impaction is a solid, immobile bulk of human feces that can develop in the rectum as a result of chronic constipation.-Symptoms:Symptoms include chronic constipation. There can be fecal incontinence and paradoxical or overflow diarrhea as liquid stool passes around the obstruction. ...

 and megarectum
Megarectum
Megarectum is a large rectum as a result of underlying nerve supply abnormalities or muscle dysfunction, which remains after disimpaction of the rectum. The Principles of Surgery textbook describes any rectum that can hold more than 1500cc of fluid as a megarectum...

, and encopresis
Encopresis
Encopresis is involuntary fecal soiling in adults and children who have usually already been toilet trained. Persons with encopresis often leak stool into their undergarments.-Prevalence:The estimated prevalence of encopresis in four-year-olds is between one and three percent...

.

Treatment

Treatments for anismus include biofeedback training, botox injections, and surgical resection.

Biofeedback
Biofeedback
Biofeedback is the process of becoming aware of various physiological functions using instruments that provide information on the activity of those same systems, with a goal of being able to manipulate them at will...

 training for treatment of anismus is highly effective.

Injections of botulin toxin type-A into the puborectalis muscle
Puborectalis muscle
The fibers which form a sling for the rectum are named the Puborectalis or Sphincter recti.They arise from the lower part of the pubic symphysis, and from the superior fascia of the urogenital diaphragm....

 are very effective in the short term, and somewhat effective in the long term. Injections may be helpful when used together with biofeedback training.

Historically, the standard treatment was surgical resection
Segmental resection
Segmental resection is a surgical procedure to remove part of an organ or gland. It may also be used to remove a tumor and normal tissue around it. In lung cancer surgery, segmental resection refers to removing a section of a lobe of the lung.- External links :* entry in the public domain NCI...

 of the puborectalis muscle. Recently, partial resection (partial division) has been reported to be effective in some cases.

Comorbidity

Anismus sometimes occurs together with other conditions that limit (see contraindication
Contraindication
In medicine, a contraindication is a condition or factor that serves as a reason to withhold a certain medical treatment.Some contraindications are absolute, meaning that there are no reasonable circumstances for undertaking a course of action...

) the choice of treatments. Thus, thorough evaluation is recommended prior to treatment.

When anismus occurs in the context of intractable encopresis
Encopresis
Encopresis is involuntary fecal soiling in adults and children who have usually already been toilet trained. Persons with encopresis often leak stool into their undergarments.-Prevalence:The estimated prevalence of encopresis in four-year-olds is between one and three percent...

 (as it often does), resolution of anismus may be insufficient to resolve encopresis. For this reason, and because biofeedback training is invasive, expensive, and labor intensive, biofeedback training is not recommended for treatment of encopresis with anismus.

Anismus may occur with anorectal malformation, rectocele
Rectocele
A rectocele results from a tear in the rectovaginal septum . Rectal tissue bulges through this tear and into the vagina as a hernia...

, rectal prolapse
Rectal prolapse
Rectal prolapse normally describes a medical condition wherein the walls of the rectum protrude through the anus and hence become visible outside the body.-Types:There are three chief conditions which come under the title rectal prolapse:...

 and rectal ulcer.

History

Anismus sometimes develops in persons with extrapyramidal motor disturbance due to Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

. This observation led in 1988 to the understanding that anismus is a type of focal dystonia
Focal dystonia
Focal dystonia is a neurological condition that affects a muscle or group of muscles in a part of the body and causes an involuntary muscular contraction or twisting...

.
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