Introduction

Anismus is a functional pooping disorder, a type of constipation, and a form of pelvic floor dysfunction where the pelvic floor muscles fail to relax properly during defecation (pooping). It is also known as dyssynergic defecation (DD) and is thought to be a behavioural disease rather than being caused by a physical or neurological source. About one-third of chronically constipated patients have an evacuation disorder, meaning they have trouble emptying their bowels, and anismus is the most common cause of pelvic evacuation disorder. It affects more women than men and can affect not just bowel habits but also urination, sexual activity, and can cause general pelvic pain.¹ This article explores the association between anismus and other pelvic floor disorders. Recognising and understanding the condition will allow us to manage the condition better.

What is Anismus?

Anismus, also known as dyssynergic defecation (DD), is a disorder of the pelvic floor that leads to incomplete emptying of stool while pooping. The pelvic floor is a group of muscles that makes up the base of your pelvis that keep your bladder, uterus, vagina, and bowel (pelvic organs) in the correct place.² 

Defecation, or pooping, is a coordinated process that involves the pelvic floor muscles and their nerves. The normal process of pooping begins with a movement called peristalsis of the large intestine (colon). This allows the food in the intestine to move along to the rectum where the stretch receptors detect the poop. The stretching initiates nerve signals that cause the relaxation of the internal anal sphincter. When a large enough force is generated by a person after the relaxation, successful defecation occurs.³ 

Anismus classically means spasm of the anus. It was first used to describe constipation in patients due to failure of the relaxation of the pelvic floor, which resulted in the spasm of the external anal sphincter while trying to poop. Many other terms such as spastic pelvic floor syndrome and obstructive defecation have been used synonymously to describe similar or the same conditions. However, the term dyssynergic defecation has since been nominated as the official term to describe the disturbance of pooping due to disruption in nerve and muscle coordination.¹

Though the exact cause of anismus is unknown, there are different proposed mechanisms of anismus:

• Hypertonic pelvic floor- pelvic floor muscles fail to relax and the poop is held in when attempting defecation
• Paradoxical contraction- instead of relaxing to allow the stool to pass through to the rectum, the muscles contract paradoxically making emptying of the bowels difficult⁴

Understanding Pelvic Floor Dysfunction

The pelvic floor is muscles and ligaments that help keep the organs in the pelvis in their right places. The organs include bladder, uterus, vagina and bowel. The muscles are essential in bodily functions such as pooping, peeing, and having sex. Dysfunction in the pelvic floor can lead to conditions like incontinence and pelvic organ prolapse.

The pelvic floor muscles are located at the base of the pelvis, creating a supportive sling for the pelvic organs. The muscles include the pubococcygeus, puborectalis, and iliococcygeus muscles collectively known as the levator ani, and the smaller coccygeus muscles at the back of the pelvis. The muscles span side to side in the pelvis and from the pubic bone to the tailbone.

Weak pelvic floor muscles can be caused by injury or trauma such as childbirth and surgery. Overuse of the pelvic floor, the natural ageing process that leads to muscle weakening, and hormonal changes such as pregnancy and menopause can lead to pelvic floor weakening. The conditions that arise from a weak pelvic floor are:

• Stress incontinence
• Urge incontinence
• Fecal incontinence
• Anal incontinence 
• Pelvic organ prolapse 

Pelvic floor muscles can also cause pelvic floor dysfunction by being too tight. It can be attributed to sexual trauma or other traumas such as accidents, childbirth, and other gynaecological conditions. This abnormally tight pelvic floor is known as hypertonic pelvic floor and leads to a myriad of conditions:

• Constipation 
• Difficulty moving your bowels
• Pelvic pain 
• Back, hip, or leg pain 
• Painful intercourse
• Difficulty peeing⁴

The Relationship Between Anismus and Pelvic Floor Disorders

The pelvic floor muscles are responsible for coordinating the process of pooping, peeing, and having sex. Anismus is a condition where there is a discoordination of the pelvic floor and is thus closely related to other pelvic floor disorders. When pelvic floor dysfunction occurs, anismus is one of the most common manifestations. It is not isolated in its presentation and often coexists with other conditions such as urinary difficulties, painful sexual intercourse (dyspareunia), and other conditions that occur due to weakness or tightening of the pelvic floor. 

Moreover, the impact of anismus extends beyond uncomfortable defecation. The improper coordination and tightening of the pelvic floor muscles can worsen or trigger additional pelvic floor disorders. Due to the interconnectedness of the conditions it is important to consider anismus as a part of a broader spectrum of pelvic floor dysfunctions.

Diagnosis of Anismus

The first step in the diagnosis of anismus is to rule out any other metabolic or pathological conditions that may be causing constipation. Slow transit constipation (STC) is the reduced motility of the large intestine due to abnormalities of the nerves that supply the intestine. STC may coexist in up to two-thirds of dyssynergic defecation cases.

Some examination methods are:

• Sigmoidoscopy- a flexible tube with a camera is introduced into the rectum to examine the lower part of the colon for any abnormalities 
• Digital rectal examination (DRE)- a healthcare professional uses a gloved finger to assess the tone of the anal sphincter muscle 
• Anorectal manometry- this measures the pressures of the anal sphincter muscles
• Balloon expulsion test- a balloon is inserted into the rectum and the patient is asked to expel it. It is used to assess the ability to perform normal bowel movements 
• Defecography and magnetic resonance defecography- imaging tests are performed while the patient attempts to poop, providing detailed images to identify functional issues
• Colonic transit study- the patient swallows radio-opaque markers and the movement of the swallowed marker is tracked through a wireless capsule or X-rays. It assesses how quickly stool passes through the large intestine⁵

To satisfy the diagnostic criteria of dyssynergic defecation there are a few things to consider. The patient must have functional constipation or IBS constipation. They must display the discoordinated pattern of the muscles when attempting to poop, and this must be confirmed by diagnostic tests such as the manometry. Additionally, the patient must have difficulty passing a simulated stool (a 50mL water-filled balloon) or show retention of poop during a barium defecography test. Colonic transit time can also be used to diagnose the patient with anismus.

Treatment and Management of Anismus

Treatment and management of anismus should be individualized, taking in the patient’s concerns and expectations. The treatment of dyssynergic defecation are:

• Standard constipation treatment- avoid constipating medications, adequate fibre and fluid intake, regular exercise, laxatives 
• Biofeedback therapy- training the body to perform normal bowel movements by correcting muscle incoordination and improving rectal sensation. It is the mainstay treatment and is considered to be very effective. Therapy involves the use of electronic devices that provide real-time feedback to the patient.
• Other measures- botulinum toxin injection, myectomy, ileostomy⁵

Additionally, pelvic floor physical therapies and relaxation techniques such as meditation and warm baths can help stretch and relax these muscles to improve coordination.⁶ 

Summary

Anismus, also known as dyssynergic defecation, is a type of pelvic floor dysfunction where the pelvic muscles fail, are discoordinated and lead to improper relaxation during pooping. This leads to chronic constipation and predominantly affects women. The condition is also associated with urination difficulties, painful or uncomfortable sexual activity, and pelvic pain. Anismus is closely related to other pelvic floor disorders and the diagnosis of anismus involves ruling out other causes of constipation using various diagnostic methods. Treatment typically involves standard constipation management, with biofeedback therapy as the mainstay. Other interventions are also considered if necessary. Proper management of anismus not only improves bowel function but also addresses related pelvic floor disorders.