Anal sphincter relaxation



Overview.

Definition

Anal sphincter relaxation refers to a functional or anatomical defect in the anal sphincter muscle, resulting in a weakened anal contraction and a series of problems such as fecal incontinence and frequent bowel movements [1-3].

The anal sphincter consists of two layers of muscles that overlap each other from inside to outside. The outer layer is the external anal sphincter, which is a skeletal muscle and a random muscle. The inner layer is the internal anal sphincter, which is a smooth muscle and an involuntary muscle. Both work together to maintain the normal function of the anus.

The main function of the anal sphincter is to control the opening and closing of the anus to maintain the normal process of defecation. During defecation, the large intestine contracts to push feces into the rectum, at which time the internal and external sphincters remain tense to keep the anus closed. As the feces enters the rectum, the pressure in the body rises and the body senses the need to have a bowel movement.

During a bowel movement, the body can consciously relax the external sphincter, causing it to relax along with the internal sphincter, which allows the anus to open and the feces to pass. When not defecating, the internal and external sphincters remain tense to prevent accidental leakage of feces.

The nerves innervating the anal sphincter are the enteric plexus, sacral nerves, and the autonomic nervous system. These nervous systems work in concert to regulate the contraction and relaxation of the anal sphincter, thereby controlling defecation.

Classification

Functional anal sphincter relaxation: mainly due to anal sphincter dysfunction resulting in relaxation, there is no obvious abnormality in the anatomical structure.

Anatomical anal sphincter relaxation: relaxation due to structural damage or defects of the anal sphincter, such as birth injury and surgery.

Etiology.

Childbirth injury, surgery, nerve injury, degenerative muscle disease, perianal disease, etc. can cause anal sphincter relaxation.

Causes

There are many causes and mechanisms of anal sphincter relaxation, here are some of the major factors [4-6].

Injury during labor and delivery

Injury to the anal sphincter can occur during labor, especially when forceps are used, when the fetus is heavy, or when labor is prolonged. Labor injury is the main cause of anatomical anal sphincter relaxation.

Surgery.

Anal surgery may cause damage to the anal sphincter, leading to anatomical anal sphincter relaxation.

Nerve Injury

Spinal cord injury, sacral nerve injury, or other neurological disorders may lead to anal sphincter dysfunction, which in turn triggers functional anal sphincter relaxation.

Muscle degeneration

As we age, the anal sphincter muscles may degenerate, leading to a decrease in anal sphincter function.

Perianal diseases

Diseases such as hemorrhoids and perianal abscesses usually do not directly cause anal sphincter relaxation, but may affect anal sphincter function due to local inflammation, pain and tissue damage.

Symptoms

Anal sphincter relaxation may present with symptoms such as fecal incontinence, frequent bowel movements, and perineal wetness.

Main Symptoms

Fecal incontinence

This is the most common symptom of anal sphincter relaxation and is characterized by involuntary leakage of gas, liquid or solid feces.

Frequent bowel movements

As the anal sphincter muscle cannot contract properly, the patient may feel frequent urge to pass stool but cannot do so.

Moisture in the perineum

The anus is unable to control fecal evacuation and defecation at will, resulting in moist perineum and contamination of clothing and pants.

Abnormal sensation

The patient may feel a foreign body sensation in the anus, a sensation of swelling or anal discomfort.

Sense of incomplete defecation

Patients may feel that there is still stool left in the anus after defecation and need to go to the toilet several times to empty it completely.

Change of stool shape

Stool may become loose or streaky as the sphincter muscle is unable to control the passage of stool through the anus properly.

Other symptoms

Paralysis of limbs, urinary disturbances

Anal sphincter relaxation due to central nervous system lesions may be combined with limb paralysis, numbness, and urinary disturbances.

Numbness of hands and feet

Diabetic autonomic neuropathy may be combined with numbness, pain and frequent urination in the hands and feet.

Complications

Infection

Due to fecal incontinence and residue, the skin around the anus is easily irritated, leading to skin inflammation, itching and infection.

Psychological effects

Anal sphincter relaxation and its symptoms can have a negative impact on a patient’s mental health, leading to anxiety, depression or social impairment.

Seek medical attention

When symptoms related to anal sphincter relaxation are detected, active medical attention is required. The doctor will ask about symptoms, medical history, previous tests and treatments.

Department of Medicine

Proctology

If you experience fecal incontinence, frequent bowel movements, or moisture in the perineum, it is recommended that you seek prompt medical attention, which may include a visit to the Department of Anorectal Medicine.

Neurology

In case of concurrent urinary incontinence, sensory and motor deficits, prompt medical attention is recommended with a visit to the Department of Neurology.

Preparation for medical treatment

Preparation for the consultation: registration, preparation of documents, common problems.

Tips for medical treatment

Before the consultation, patients can organize their symptoms, duration, pain level and other relevant information. If the patient has other medical conditions or is taking medication, he/she should also inform the doctor of these conditions.

Preparation Checklist for Medical Consultation

Symptom checklist

Particular attention should be paid to the time of onset of symptoms, special manifestations, etc.

Is there any fecal incontinence, frequent bowel movements? When did the symptoms start and how long did they last?

How often do the symptoms occur?

Under what circumstances is the incontinence aggravated or relieved?

Is there any change in the volume of bowel movements? What is the nature of the stool?

Is there a foreign body sensation in the anus? Is there a feeling of incomplete evacuation?

Is the perineum moist?

Is it accompanied by abdominal pain, diarrhea, constipation, nausea, vomiting?

Is there any limb weakness, numbness, urinary incontinence?

List of medical history

Are there any diabetes mellitus, neurological diseases?

Has there been any previous anal surgery?

Are there any anal or bowel disorders?

If female, is there a history of childbirth? Was the mode of delivery normal or cesarean?

Checklist

Test results for the last six months, which can be brought to the doctor’s office

Endoscopy: including anoscopy, proctoscopy and colonoscopy

Imaging: intrarectal ultrasound or MRI, abdominopelvic CT and MRI, spinal cord and cranial MRI, etc.

Other tests: fecography, anal sphincter electromyography, anorectal pressure.

Diagnosis

Anal sphincter relaxation relies on history, symptoms, anal sphincter electromyography, and other tests to make a definitive diagnosis.

Diagnosis is based on

Medical history

History of diabetes mellitus, neurologic disorders.

History of anorectal surgery.

History of anorectal disease.

History of birth injury in females.

Clinical manifestations

Symptoms

Patients may present with symptoms such as fecal incontinence, frequent bowel movements but no bowel movement.

Physical signs

Anorectal palpation reveals decreased anal sphincter tension, decreased contractility, and decreased anal pressure to finger.

Anal sphincter electromyography

is a test that evaluates muscle and nerve function and can help diagnose anal sphincter relaxation.

During the examination, the electrophysiologic activity of the anal sphincter during rest, contraction, and relaxation can be recorded by means of a muscle electrode inserted into the anus.

The resting electrical activity during anal sphincter relaxation may be attenuated or the waveform flattens out; the electrical activity during active contraction may be attenuated with a decrease in waveform amplitude; and the electrical activity during exsufflation may fluctuate with little fluctuation or a decrease in waveform amplitude [7].

Anorectal manometry

To check the sensitivity, coordination and function of the rectal and anal sphincters.

By means of a pressure transducer inserted into the anus, the pressure of the anal sphincter and rectum is measured at rest, contraction and relaxation.

The resting pressure in the anus during anal sphincter relaxation and the pressure during active contraction were reduced, suggesting reduced anal sphincter tension. During anal manometry, the physician performs dilatation stimulation of the rectum and observes the rectal sensory reflex. Those with anal sphincter relaxation are insensitive or unresponsive to rectal dilatation stimulation.

Endoscopy

Endoscopy includes anoscopy, proctoscopy and colonoscopy. It is used to clarify the presence of mucosal inflammation, tumors, and hemorrhoids in the colon, rectum, and anus.

Imaging

Intrarectal ultrasound or MRI, CT and MRI of the abdominal and pelvic cavity to detect lesions and occupations in the abdominal and pelvic cavity.

Spinal cord and cranial MRI are used to rule out central nervous system lesions.

Defecography

Includes barium fecography or MRI fecography. It is used to assess anal sphincter length, anorectal angle, pelvic floor descent, and to detect rectal bulge and rectal prolapse.

Differential diagnosis

Anal sphincter relaxation needs to be differentiated from the following conditions:

Hemorrhoids

Similarities: severe hemorrhoids may lead to fecal incontinence.

Differences: Hemorrhoids are dilated, varicose, and inflamed lesions of the venous plexus in the anus and rectum, along with symptoms such as lumps, bleeding, itching, and pain, which may not be present with anal sphincter laxity.

Rectal prolapse

Similarities: Rectal prolapse may also lead to fecal incontinence and difficulty in passing stool, similar to anal sphincter relaxation.

Differences: Patients with rectal prolapse may show signs of rectal tissue protruding from the anus, whereas those with anal sphincter laxity may not.

Treatment

Aim of treatment: Improve the strength and tension of the anal sphincter, improve the symptoms of fecal incontinence and difficulty in defecation, and improve the patient’s quality of life.

Treatment principle: according to the patient’s symptoms, severity, anal sphincter function examination results and individual differences, formulate a personalized treatment plan [8-10].

Conservative treatment

Lifestyle intervention

Adjust dietary habits and increase dietary fiber intake.

Maintain regular bowel habits.

Perineal Functional Exercise

It is unlikely that an increase in tension in the internal anal sphincter will be achieved through perineal strength exercises, but this exercise program may increase muscle volume and voluntary contraction of the external anal sphincter, puborectalis ring, and anal raphe.

Medication.

Anti-inflammatory, antidiarrheal, and intestinal motility-reducing medications are chosen to improve symptoms.

Commonly used drugs include mesalazine, olsalazine, montelukast, loperamide hydrochloride, and polyethylene glycol.

Medication is suitable for patients with mild symptoms.

Biofeedback

An extracorporeal device is used to help patients strengthen their pelvic floor muscles through exercise, cognitive retraining of the pelvic floor and abdominal wall musculature, and enhancement of the patient’s ability to control bowel movements. This technique has become one of the mainstays of conservative treatment.

Sacral Nerve Stimulation

The sacral nerve controls the anal sphincter, colon and rectum. Stimulation of the sacral nerves using electrical impulses produces regular contractions of the anal sphincter, which helps to restore the normal functioning of the nerves, resulting in accurate control of bowel movements.

Patients using this therapy should first undergo biofeedback training as pre-treatment.

This therapy should be reserved for consideration after all conservative treatments have failed.

Acupuncture therapy

For anal sphincter relaxation due to peripheral nerve injury, acupuncture can be performed at points such as Changqiang, Baihui, and Chengshan.

Surgical treatment

Anal sphincter angioplasty is indicated for patients who fail to receive the above treatments and have structural damage to the anal sphincter as confirmed by vaginorectal ultrasound or MRI.

Anal sphincter repair

Repair of anal sphincter damage and improvement of sphincter strength. Suitable for patients with dysfunction caused by anal sphincter damage.

Artificial anal sphincter implantation

Implantation of a controlled artificial anal sphincter to improve sphincter strength. This procedure is indicated for patients with severely reduced anal sphincter function.

Colostomy

Colostomy is indicated in severe cases, but the quality of life after surgery has to be evaluated.

Prognosis

The symptoms of anal sphincter relaxation can be significantly improved by active treatment.

Cure

Generally, with aggressive treatment and rehabilitation, many patients experience significant improvement in their symptoms.

Harmful effects

Long-term anal incontinence can lead to a decrease in the patient’s quality of life, affecting work and daily life.

Anal incontinence may lead to severe psychological stress, such as anxiety and depression. Patients may avoid social activities because of their condition, leading to impaired relationships.

Daily

Patients with anal sphincter relaxation need to pay attention to their diet, strengthen their daily management and have regular follow-ups.

Daily management

Dietary management

Maintain a balanced diet and increase dietary fiber intake in order to maintain normal bowel function.

Avoid excessive intake of fat and spicy food to avoid intestinal irritation.

Lifestyle Management

Try to have regular bowel movements to avoid prolonged constipation or diarrhea.

Increase physical activity and strengthen pelvic floor muscle exercise to enhance sphincter function.

Reduce obesity to decrease pelvic pressure.

Sitting and standing for a long time will increase pelvic pressure and aggravate symptoms, avoid sitting and standing for a long time.

Psychological support

Maintain a good state of mind and reduce psychological pressure.

Disease monitoring

Indicators that patients need to be monitored include the number of bowel movements, the degree of difficulty in defecation and the character of the stool. Regular pelvic floor muscle strength testing can be performed if needed.

Follow-up review

Review should be scheduled according to the patient’s condition and the doctor’s recommendation.

Items to be reviewed include rectal examination, anal manometry and anal ultrasound.

Prevention

Maintain a balanced diet and increase dietary fiber intake to maintain normal bowel function.

Increase physical activity and strengthen pelvic floor muscle exercise to enhance sphincter function.

Pay attention to bowel regularity and treat constipation in time to avoid continuous pressure on the sphincter.