Introduction

Anismus also known as dyssynergic defecation is a health condition which involves difficulty in passing stools due to dysfunction in the pelvic floor. This condition may cause pain and obstructive constipation (difficulty passing stools). 

Anismus is one of the leading causes of chronic constipation. The aetiology of anismus remains unknown.¹ Patients suffering from this condition can irritate the pelvic floor muscles by constantly straining the pelvic muscles in an attempt to have a bowel movement. 

Other complications include faecal impaction (retention of a mass of hard stool), faecal incontinence (inability to hold stools), and megarectum (an enlargement of the diameter of the rectum). Anismus leads to an impairment in the mental, social, and physical well-being of the patients.² 

Timely diagnosis and management of anismus might significantly improve the general well-being of the patients and improve their quality of life.

Understanding anismus

What is anismus?

Anismus means spasm of the anus. It is also known as dyssynergia defecation since it is caused by abnormal neuromuscular coordination between abdominal, rectoanal, and pelvic floor muscles, leading to difficulty passing stools. 

Pelvic floor muscles support the bowel, bladder, and uterus. Contracting these muscles lifts the internal organs and tightens the openings of the vagina, anus, and urethra. Relaxing the pelvic floor muscles allows the passage of urine and faeces. 

Pelvic floor dysfunction causes the inability to relax and coordinate muscles in the pelvic floor to have bowel and bladder movements. Anismus can cause hard, infrequent stools in patients. Patients might feel a sensation of incomplete emptying of the rectum during or after defecation. 

Anismus may lead to problems like stool retention of any type of consistency, or faecal impaction (retention of stool that has a hardened consistency), which can cause stretching of the walls of the rectum and the colon. Additionally, liquid stools may leak around faecal impaction causing faecal incontinence in some patients.

Causes and risk factors

The exact cause of anismus is unclear. Results from 118 dyssynergia patients enrolled in a prospective study indicated that 29% of patients started experiencing this condition after events such as back injury, pregnancy, or trauma; 31% of patients started experiencing this condition during childhood; and no cause could be established for 40% of the patients.² 

Anismus can be a consequence of various underlying factors such as:

• Physiological changes occurring during pregnancy and childbirth
• Traumatic incidents especially back injury
• Inappropriate toilet habits such as excessive straining while defecating, sitting on the toilet for a long time, etc)
• Inappropriate learning of defecation during childhood as a result of behavioural problems or parent-child conflicts
• Neurological disturbances between the brain-gut axis
• Rectal hyposensitivity (reduced rectal sensation)
• Mental health issues like anxiety and/or psychological stress
• History of sexual abuse

Symptoms

Patients suffering from anismus experience a variety of bowel symptoms such as:

• Chronic constipation characterised by less than 3 bowel movements per week
• Changes in stool consistency; hard or lumpy stools.
• The feeling of incomplete evacuation or obstruction²
• Using fingers to facilitate pooping²
• Excessive straining while pooping²
• Anorectal pain
• Abdominal pain and discomfort
• Abdominal bloating²

Diagnosis

Diagnosis begins with a thorough examination of the abdomen and the area around the anus and rectum by the healthcare provider. Healthcare providers will try to rule out other causes of constipation such as disease, injury, or inflammation. A definitive diagnosis of anismus can be made only after doing one or more tests as mentioned below:

Anorectal manometry

Anorectal manometry is a test that measures contractions and relaxations of the anal muscles along with the sensation and reflex activity in the rectum. 

The test is performed by inserting a small flexible tube with a balloon on the end into the anus of the patient, while the patient is lying down comfortably. This test takes about an hour. It is an essential test for a diagnosis of anismus. The test can detect:

• Whether or not a patient can generate adequate pushing force
• Whether anal sphincter muscles relax and tighten sufficiently in response to pushing
• Whether or not rectal sensation is in the normal range

Balloon expulsion test

A balloon expulsion test examines the relaxation of the pelvic floor and opening of the anal canal by measuring the length of time taken by the patient to pass stool from the rectum. 

For this test, a balloon inflated with warm water is used to stimulate bowel movement. The healthcare technician places the balloon in the rectum and inflates it to a certain level after which, the patient, in private, expels the balloon. 

If a patient is unable to expel the balloon within a minute, anismus is suspected. This test is more successful in ruling out anismus than diagnosing it.

Defecography 

Defecography uses an X-ray machine or magnetic resonance imaging (MRI) to record moving images of a semi-solid paste (barium) as it passes through the rectum. The barium paste passes like a soft stool and provides useful information about the movement of muscles and organs. 

The test can help in the diagnosis of pelvic floor dysfunction along with other structural abnormalities contributing to anismus. 

Certain co-existing conditions may need to be ruled out before confirming the diagnosis of anismus. Tests like blood tests, Sigmoidoscopy (examination of the inside of the sigmoid colon and rectum using a tube), and colonic transit time tests can be done to exclude other conditions.

Treatment

The management of anismus is individualised based on the patient's symptoms, concerns, and other coexisting conditions. The standard management consists of treatment of constipation, biofeedback therapy, and invasive procedures such as Botox injections.

Standard treatment for constipation

Avoiding constipation medications

Medications known to induce constipation eg. antacids, iron or calcium supplements, non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen), antidepressants, antihistamines (such as cetirizine), antiepileptics (i.e., carbamazepine) should be avoided.

Adequate fluid intake 

An increase in daily consumption of water from 1 litre to 2 litres increases defecation frequency in patients with chronic constipation. However, there is no evidence suggesting that constipation can successfully be treated by increasing fluid intake unless there is evidence of dehydration³

Fibre intake

A high-fibre diet (natural or supplemental) is highly beneficial in patients with mild to moderate constipation. High-fibre diet bulks up the stool, softens the stool by absorbing water, increases the frequency of stools, and helps in maintaining the healthy gut microbiota composition.^{4, 5} It also decreases dependence on laxatives⁶ 

A daily intake of 25 g is recommended to improve symptoms, increase defecation frequency, and reduce the use of laxatives. However, it is important to recommend that patients increase their water intake while taking fibres to avoid hard and bulky stools^{6, 7} 

Some side effects of a diet with a high fibre intake include abdominal bloating, flatulence, and abdominal discomfort. Patients with anismus respond poorly to fibre supplementation compared to those without any motility disorder.⁸

Toilet training

Patients are also educated to attempt to defecate at least twice a day (after waking up and 30 minutes after a meal) and to avoid postponing it. Patients are advised to strain only up to 50%-70% of their maximum effort for at least 5 minutes.⁷

Pharmacologic therapy

Laxatives such as bisacodyl, lactulose, etc can be used for the treatment of patients with chronic constipation. Although laxatives alone may not be as effective in treating anismus, they can be promising when used in combination with biofeedback therapy. 

Biofeedback therapy

Biofeedback therapy (BFT) has proven to be an effective technique in the management of anismus. It utilises data from normal physiological processes, such as muscle contraction and relaxation patterns, to generate visual or auditory feedback signals. Through guided exercises, patients are trained to voluntarily control and relax their sphincter muscles.

BFT helps patients in restoring normal defecation patterns by coordinating abdominal activity with the muscles involved in bowel movements, including the rectal, puborectalis, and anal sphincter muscles. 

This is achieved by increasing abdominal pressure while simultaneously relaxing the pelvic floor muscles and anal sphincters. Additionally, simulated defecation and sensory training of the rectum are often incorporated into BFT sessions.

Research has shown that BFT can be more effective than dietary changes or the use of laxatives in treating anismus.⁹ However, the success of BFT depends on factors such as the patient's level of motivation and attention.

Benefits of BFT include improvements in bowel movements, stool consistency, reduced straining, alleviation of the sensation of incomplete evacuation, and overall enhancement in the quality of life for patients with anismus.

Botox injections 

A study conducted in patients with anismus who were unresponsive to simple biofeedback training showed that botulinum toxin type A injections in the puborectalis (pelvic floor muscle) and external anal sphincter (skeletal muscle surrounding the inferior portion of the anal canal) proved to be an effective treatment in the management of anismus.¹⁰

Summary

Anismus, also called dyssynergic defecation is a health condition characterised by difficulty in pooping due to problems with the pelvic floor muscles. Anismus accounts for most of the cases of chronic constipation. This condition hurts the quality of life, along with the physical and mental well-being of the patient. 

The exact cause of anismus remains unknown, however, certain risk factors include injury, history of sexual abuse, pregnancy, stress, and bad toilet habits. Common symptoms of anismus include chronic constipation, difficulty passing stools, abdominal pain, discomfort, and bloating. 

Diagnosis involves a detailed history and an examination such as a digital rectal examination, anorectal manometry and balloon expulsion test. Individualised treatment based on symptoms can help patients in the management of anismus. Improvement in the patient’s condition can be seen after increasing daily fluid intake, consuming a lot of fibre, and getting a lot of exercise. Treatment modalities like feedback therapy have shown to be effective in patients and can improve their quality of life.