[citation needed] Symptoms include tenesmus (the sensation of incomplete emptying of the rectum after defecation has occurred) and constipation.

It can also be treated with a type of biofeedback therapy, during which a sensor probe is inserted into the person's anal canal in order to record the pressures exerted by the pelvic floor muscles.

These pressures are visually fed back to the patient via a monitor who can regain the normal coordinated movement of the muscles after a few sessions.

Some researchers have suggested that anismus is an over-diagnosed condition, since the standard investigations of digital rectal examination and anorectal manometry were shown to cause paradoxical sphincter contraction in healthy controls, who did not have constipation or incontinence.

[1] Due to the invasive and perhaps uncomfortable nature of these investigations, the pelvic floor musculature is thought to behave differently compared to normal circumstances.

[citation needed] The rectum is a section of bowel situated just above the anal canal and distal to the sigmoid colon of the large intestine.

It is believed to act as a reservoir to store stool until it fills past a certain volume, at which time the defecation reflexes are stimulated.

The internal anal sphincter is not under voluntary control, and in normal persons it is contracted at all times except when there is a need to defecate.

The point at which the rectum joins the anal canal is known as the anorectal ring, which is at the level that the puborectalis muscle loops around the bowel from in front.

[5] Conversely, relaxation of the puborectalis reduces the pull on the junction of the rectum and the anal canal, causing the anorectal angle to straighten out.

Contraction of the external sphincter can defer defecation for a time by pushing stool from the anal canal back into the rectum.

Once the voluntary signal to defecate is sent back from the brain, the abdominal muscles contract (straining) causing the intra-abdominal pressure to increase.

[citation needed] In patients with anismus, the puborectalis and the external anal sphincter muscles fail to relax, with resultant failure of the anorectal angle to straighten out and facilitate evacuation of feces from the rectum.

[7] One paper stated that events such as pregnancy, childbirth, gynaecological descent or neurogenic disturbances of the brain-bowel axis could lead to a "functional obstructed defecation syndrome" (including anismus).

[13] Some authors have commented that the "puborectalis paradox" and "spastic pelvic floor" concepts have no objective data to support their validity.

They state that "new evidence showing that defecation is an integrated process of colonic and rectal emptying suggests that anismus may be much more complex than a simple disorder of the pelvic floor muscles.

[24] The Rome II classification functional defecation disorders were divided into 3 types,[25] however the symptoms the patient experiences are identical.

The anorectal angle has been shown to flatten out when in a squatting position, and is thus recommended for patients with functional outlet obstruction like anismus.

[5] If the patient is unable to assume a squatting postures due to mobility issues, a low stool can be used to raise the feet when sitting, which effectively achieves a similar position.

[40] The researchers drew analogies to a condition called vaginismus, which involves paroxysmal (sudden and short lasting) contraction of pubococcygeus (another muscle of the pelvic floor).