Anorectal manometry

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Anorectal manometry
Anorectum.gif
Diagram of the anorectum. This is the location where the probe is inserted and where pressures are measured.
OPS-301 code 1-315

Anorectal manometry (ARM) is a medical test used to measure pressures in the anus and rectum and to assess their function. [1] [2] The test is performed by inserting a catheter, that contains a probe embedded with pressure sensors, through the anus and into the rectum. [3] Patients may be asked to perform certain maneuvers, such as coughing or attempting to defecate, to assess for pressure changes. [3] Anorectal manometry is a safe [4] and low risk [3] procedure.

Contents

From 2014 to 2018, the international anorectal physiology working group (IAPWG) meet several times to develop consensus on indications for anorectal manometry. [5] Their assessment concluded that anorectal manometry was indicated when used in assessment of fecal incontinence, constipation, evacuation disorders (including Hirschsprung's disease [6] ), functional anorectal pain and in the assessment of anorectal function preoperatively or after a traumatic obstetric injury. [5] In addition to the indications outlined by the IAPWG, anorectal manometry has been used as a component of anorectal biofeedback. [6]

Since its introduction in 2007, high resolution anorectal manometry (HR-ARM) has increasingly replaced conventional anorectal manometry as the standard. [7] There has been increasing usage of high-definition (3D) anorectal manometry (HD-ARM) as well. [7] Current advances in anorectal manometry include the development of bedside portable technology. [7]

Medical uses

Fecal incontinence

After eliminating structural causes of fecal incontinence from the differential diagnosis, anorectal manometry may be used to evaluate deficiencies in sphincter function or anorectal sensation. [4] [7] An abnormal resting pressure or squeeze pressure may indicate problems with either the internal anal sphincter or the external anal sphincter respectively. [4] Both increased and decreased anorectal sensation has also been detected in individuals with fecal incontinence. [6] The use of HD-ARM can allow recognition of pressure asymmetry within the anorectum. [4] Some patients with fecal incontinence benefit from muscle strength training which may make use of anorectal biofeedback. [6]

Constipation

Anorectal manometry can be used in the diagnostic workup of individuals with chronic constipation without a known cause [8] or with chronic constipation that has not improved on a trial of laxatives and/or fiber. [9] For example, on a digital rectal exam, a physician may notice specific findings that point to dyssynergic defecation, a cause of chronic constipation. [8] In such instances, the physician may order an anorectal manometry study to verify their findings. [8] Abnormal results, such as the presence of a paradoxical contraction of the anal sphincter muscles during defecation (i.e. the muscles are squeezing instead of relaxing), can also be used to guide treatment (e.g. anorectal biofeedback). [4] [8] Other abnormal findings on manometry consistent with chronic constipation include an unsatisfactory generation of the propulsive force needed to defecate and a decreased movement of pelvic floor muscles. [4]

Anorectal manometry, especially HR-ARM and HD-ARM, has also been used to evaluate constipation due to structural causes such as a rectocele, [2] an enterocele, or an intra-anal intussusception. [4]

Hirschsprung's disease

In infants and children, anorectal manometry may be used to assist in the diagnosis of Hirschsprung's disease. [2] The absence of the rectoanal inhibitory reflex (RAIR) is almost always pathognomonic for Hirschsprung's disease in this population. [6] Anorectal manometry is not significantly less sensitive and specific when compared to the gold standard method of diagnosis, rectal suction biopsy. [6] In adults, the absence of the RAIR is less likely due to Hirschsprung's disease and may indicate the presence of megarectum. [6] [7]

Functional anorectal pain

Functional anorectal pain includes disorders such as levator ani syndrome, proctalgia fugax and unspecified functional anorectal syndrome. [4] Although diagnosis of these disorders is largely clinical, anorectal manometry may be used for further diagnostic assessment. [4] For example, the degree of anal sphincter hypertension may be determined [7] which may be useful information when treating functional anorectal pain with biofeedback therapy. [4]

Biofeedback

The goal of anorectal biofeedback is to help patients improve defecating behaviors by providing patients with visual and verbal feedback. [10] Visual feedback tools, such as anorectal manometry, are often used to aid patients in learning how to modify their behaviors. [10] Patients may work on improving muscle strength, muscle relaxation or sensation during defecation. [8]

The effectiveness of anorectal biofeedback as a treatment remains an ongoing source of debate and research. A systemic review article [11] concluded that although better than placebo, there remained limited evidence demonstrating the effectiveness of anorectal biofeedback for chronic idiopathic constipation. [8] In patients with defecatory disorders, including dyssynergic defecation, pelvic floor biofeedback therapy had been shown to be more effective than laxatives. [6] [9] An American-European Neurogastroenterology & Motility task force (ANMS-ESNM) recommended the use of biofeedback in the short and long treatment of constipation with dyssynergic defecation and fecal incontinence. [10] They did not recommend biofeedback treatment for constipation without dyssynergic defecation, nor in children with constipation. [10]

Types

Types of anorectal manometry include:

HR-ARM and HD-ARM are newer methods that use multiple closely spaced sensors in the anus and rectum, compared to 3-6 widely spaced sensors used by non-HRM, to generate a more refined view. [3] [6] An additional benefit to HR-ARM and HD-ARM is the increased ease in analyzing the results as pressure readings are displayed in both color and as a line plot. [3] Accompanying the benefits shared by both high-resolution and high-definition methods, the HD-ARM method employs additional sensors placed circumferentially around the catheter allowing for closer interpretation of individual sensor pressure readings. [3] In comparison to non-HRM, however, both of the newer methods utilize equipment that is more expensive and has a shorter design life. [3]

Procedure

Equipment

The specifics of the equipment used for the procedure will ultimately depend on the type of manometry and the manufacturer of the device. Nonetheless, most share some common features: [3]

Technique

In 2019, the International Anorectal Physiology Working Group (IAPWG) released a standardized testing protocol for the use of anorectal manometry. [5] One of the goals of this protocol was to standardize procedural techniques to better facilitate meaningful data sharing. [5] This protocol is the most recent published guideline for anorectal manometry since the one published in 2002 [12] which was not widely adopted. [7]

Preparation

Fasting is not a requirement for this procedure. [5] Patients are informed as to how the procedure is performed, its benefits and risks. Risks include the possibility of developing discomfort, pain, minor bleeding, dizziness or a rare perforation. [3] [13] In the testing room, the patient is placed on their left side with their knees bent. [5] A digital rectal exam is then performed prior to the procedure to evaluate initial anatomy and function, check for stool, and to assess patient's understanding of the verbal instructions employed during the procedure. [5]

Tests

Anorectal manometry is often performed alongside a rectal sensory test (RST) and a balloon expulsion test (BET). [5] The RST is performed after the manometry while the BET may be performed immediately prior to the manometry or subsequent to the RST. [5] The total time to conduct all three tests is 15 to 20 minutes. [5]

Manometry

This test takes approximately 10 minutes. [5] With the use of a lubricant, an anorectal manometry catheter is introduced into the anus. [5] The catheter is advanced until the base of the balloon is above the anal canal by 3–5 cm (1.2–2.0 in) and the most distal sensor is below the anal verge. [5] In order, the following maneuvers are then performed:

Descriptions and purpose of maneuvers performed during manometry test [5]
ManeuverDescriptionPurposeLength of Time
StabilizationNo instructionAllow return to baseline3 minutes
RestPatient asked to restMeasure resting pressure, detect presence of ultraslow waves60 seconds
Short squeezeSqueeze as if preventing expulsion of feces or flatus Measure squeeze pressure3 five second squeezes each separated by 30 seconds of recovery
Long squeezeSqueeze as if preventing expulsion of feces or flatus Measure squeeze pressure30 seconds followed by a 60-second interval of recovery
CoughCough onceMeasure changes in pressure during cough1 cough followed by a 30-second interval of recovery followed by another 1 cough
PushPush as if defecatingMeasure changes in pressure during defecation, detect presence of RAIR 3 fifteen second pushes separated by 30 seconds of recovery
RST

During the rectal sensory test, air is placed into the catheter balloon and slowly inflated either continuously or step-wise. [5] The patient is asked to verbalize when they first sense the balloon, when the urge to defecate is first present and when they can no longer tolerate the balloon. [5]

BET

To perform the balloon expulsion test, a catheter with a balloon on its tip is introduced into the patient's anorectum. [5] The balloon is then distended to 50ml with water. [5] Patients are then instructed to transfer from lying on their side to sitting on a toilet. [5] Next, patients are asked to push out the balloon as if they are defecating. [5] The time it takes for the expulsion of the balloon is then recorded. [5]

Analysis

Resting pressure

The anal resting pressure is the recorded pressure within the anus during muscle relaxation. [6] After insertion of the catheter, a short amount of time is allowed for the muscles to relax. Afterwards, pressures are recorded over 60 seconds. [5] The maximum resting pressure is the highest pressure reached during this time period, while the mean resting pressure is the average pressure during this time period. In healthy individuals, women, especially older women, have an average lower anal resting pressures than men. [6]

Squeeze pressure

The anal squeeze pressure is the recorded pressure within the anus during a voluntary contraction of the external anal sphincter. [6] Similar to resting pressures, squeeze pressures in healthy women are lower than healthy men. [6] If using high-definition anorectal manometry, asymmetry in squeeze pressures can also be measured. [6]

Change of pressure during defecation

During defecation, the pressure in the anorectum should increase while the external anal sphincter should relax. If the pressure difference during defecation does not increase sufficiently, it may indicate poor propulsive force. [6] [14] Additionally, inadequate relaxation of the sphincter during defecation is another abnormal finding. [6] Another method to assess changes during defecation is to calculate an anorectal gradient (or defecation index) in one of two ways. [14] The anorectal gradient is either calculated as a difference (rectal pressure - anal pressure) or as a ratio (rectal pressure / anal pressure). [14] A positive difference or a ratio over 1 indicates normal findings. [14] Abnormal findings on manometry does not definitively indicate illness as a significant number of healthy individuals have been found to have abnormal results. [6] [14] Values recorded during a defecation trial are influenced by a number of factors including the degree of patient involvement in defecation efforts. [6]

Rectoanal inhibitory reflex (RAIR)

In healthy individuals, in the process of defecating, the internal anal sphincter will reflexively relax. The lack of a rectoanal inhibitory reflex may indicate either the absence or the non-functionality of certain muscle or nerve structures involved in proper defecation. [3] [6]

Sensation

Patients are assessed on their anorectal sensory perception via the inflation of a balloon. As the balloon is inflated, its volume is recorded at certain milestones: [5] initial sensation of the equipment, start of the sensory urge to defecate and the point of maximum discomfort. [6] [3] An increased level of sensation has been noted in disorders such as fecal incontinence, while a decreased level of sensation has been seen in individuals with dyssynergic defecation. [3]

Interpretation

As part of the 2020 IAPWG consensus manuscript, the group published the newly created London Classification for Disorders of Anorectal Function which aimed to standardize the interpretation of anorectal manometry findings. [5] [7] The London Classification divided disorders into 4 parts:

London Classification for Disorders of Anorectal Function [5] [7]
PartDisorder
1Disorder of the RAIR
2Disorders of anal tone and contractility
3Disorders of rectoanal coordination
4Disorders of rectal sensation

Under each part, there are a list of diagnosis that are made based on manometry findings. For example, under part 2 (Disorders of anal tone and contractility), listed manometric diagnoses include: anal hypotension, anal hypertension, anal hypercontractility and combined anal hypertension and hypercontractility. [7] Findings are also divided into: major findings, minor findings and inconclusive findings. [7] Major findings are findings that are not present in healthy patient such as rectoanal areflexia, [7] Minor findings are findings that are more commonly found in patients with anorectal disease compared to healthy patients, while inconclusive findings are findings that may be present in both groups. [7]

Limitations

Centers rely on published data sets from healthy volunteers to evaluate test findings. [4] However, the lack of standardization in equipment usage and procedural protocol, can in certain cases, impact the ability to determine what may be considered normal or abnormal values. [4] This is further complicated by the limited amount of data on the impact of different epidemiological characteristics (such as age or gender) on said values. [4] For an individual patient, findings on anorectal manometry, alone, does not dictate management. [7] In addition to correlating manometry findings with clinical findings, as part of a diagnostic or evaluatory workup, the use of anorectal manometry may be complemented with other diagnostic tests such as endoanal ultrasound, defecography or gut transit studies. [7] High resolution anorectal manometry also experiences pressure drift, variable linear changes in pressure readings over time, that could impact the clinical value of manometry findings in some specific situations. [6]

See also

Related Research Articles

<span class="mw-page-title-main">Fecal incontinence</span> Inability to refrain from defecation

Fecal incontinence (FI), or in some forms, encopresis, is a lack of control over defecation, leading to involuntary loss of bowel contents — including flatus (gas), liquid stool elements and mucus, or solid feces. FI is a sign or a symptom, not a diagnosis. Incontinence can result from different causes and might occur with either constipation or diarrhea. Continence is maintained by several interrelated factors, including the anal sampling mechanism, and incontinence usually results from a deficiency of multiple mechanisms. The most common causes are thought to be immediate or delayed damage from childbirth, complications from prior anorectal surgery, altered bowel habits. An estimated 2.2% of community-dwelling adults are affected. However, reported prevalence figures vary. A prevalence of 8.39% among non-institutionalized U.S adults between 2005 and 2010 has been reported, and among institutionalized elders figures come close to 50%.

<span class="mw-page-title-main">Esophageal motility study</span> Medical test

An esophageal motility study (EMS) or esophageal manometry is a test to assess motor function of the upper esophageal sphincter (UES), esophageal body and lower esophageal sphincter (LES).

<span class="mw-page-title-main">Anal fissure</span> Break or tear in anal canal skin

An anal fissure is a break or tear in the skin of the anal canal. Anal fissures may be noticed by bright red anal bleeding on toilet paper and undergarments, or sometimes in the toilet. If acute they are painful after defecation, but with chronic fissures, pain intensity often reduces and becomes cyclical.

<span class="mw-page-title-main">Rectal prolapse</span> Protrusion of the walls of the rectum outside the body

A rectal prolapse occurs when walls of the rectum have prolapsed to such a degree that they protrude out of the anus and are visible outside the body. However, most researchers agree that there are 3 to 5 different types of rectal prolapse, depending on whether the prolapsed section is visible externally, and whether the full or only partial thickness of the rectal wall is involved.

Functional constipation, also known as chronic idiopathic constipation (CIC), is defined by less than three bowel movements per week, hard stools, severe straining, the sensation of anorectal blockage, the feeling of incomplete evacuation, and the need for manual maneuvers during feces, without organic abnormalities. Many illnesses, including endocrine, metabolic, neurological, mental, and gastrointestinal obstructions, can cause constipation as a secondary symptom. When there is no such cause, functional constipation is diagnosed.

<span class="mw-page-title-main">Colorectal surgery</span> Field in medicine for disabilities in the rectum

Colorectal surgery is a field in medicine dealing with disorders of the rectum, anus, and colon. The field is also known as proctology, but this term is now used infrequently within medicine and is most often employed to identify practices relating to the anus and rectum in particular. The word proctology is derived from the Greek words πρωκτός proktos, meaning "anus" or "hindparts", and -λογία -logia, meaning "science" or "study".

The rectoanal inhibitory reflex (RAIR), also known as the anal sampling mechanism, anal sampling reflex, rectosphincteric reflex, or anorectal sampling reflex, is a reflex characterized by a transient involuntary relaxation of the internal anal sphincter in response to distention of the rectum. The RAIR provides the upper anal canal with the ability to discriminate between flatus and fecal material.

<span class="mw-page-title-main">Defecography</span> Visualisation of the mechanics of a patients defecation

Defecography is a type of medical radiological imaging in which the mechanics of a patient's defecation are visualized in real time using a fluoroscope. The anatomy and function of the anorectum and pelvic floor can be dynamically studied at various stages during defecation.

<span class="mw-page-title-main">Rectum</span> Final portion of the large intestine

The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The adult human rectum is about 12 centimetres (4.7 in) long, and begins at the rectosigmoid junction at the level of the third sacral vertebra or the sacral promontory depending upon what definition is used. Its diameter is similar to that of the sigmoid colon at its commencement, but it is dilated near its termination, forming the rectal ampulla. It terminates at the level of the anorectal ring or the dentate line, again depending upon which definition is used. In humans, the rectum is followed by the anal canal, which is about 4 centimetres (1.6 in) long, before the gastrointestinal tract terminates at the anal verge. The word rectum comes from the Latin rēctumintestīnum, meaning straight intestine.

<span class="mw-page-title-main">Human anus</span> External opening of the rectum

In humans, the anus is the external opening of the rectum located inside the intergluteal cleft. Two sphincters control the exit of feces from the body during an act of defecation, which is the primary function of the anus. These are the internal anal sphincter and the external anal sphincter, which are circular muscles that normally maintain constriction of the orifice and which relax as required by normal physiological functioning. The inner sphincter is involuntary and the outer is voluntary. Above the anus is the perineum, which is also located beneath the vulva or scrotum.

Solitary rectal ulcer syndrome or SRUS is a chronic disorder of the rectal mucosa. It commonly occurs with varying degrees of rectal prolapse. The condition is thought to be caused by different factors, such as long term constipation, straining during defecation, and dyssynergic defecation. Treatment is by normalization of bowel habits, biofeedback, and other conservative measures. In more severe cases various surgical procedures may be indicated. The condition is relatively rare, affecting approximately 1 in 100,000 people per year. It affects mainly adults aged 30–50. Females are affected slightly more often than males. The disorder can be confused clinically with rectal cancer or other conditions such as inflammatory bowel disease, even when a biopsy is done.

<span class="mw-page-title-main">Anismus</span> Failure to relax the pelvic floor muscles during defecation

Anismus or dyssynergic defecation is the failure of normal relaxation of pelvic floor muscles during attempted defecation. It can occur in both children and adults, and in both men and women. It can be caused by physical defects or it can occur for other reasons or unknown reasons. Anismus that has a behavioral cause could be viewed as having similarities with parcopresis, or psychogenic fecal retention.

Obstructed defecation syndrome is a major cause of functional constipation, of which it is considered a subtype. It is characterized by difficult and/or incomplete emptying of the rectum with or without an actual reduction in the number of bowel movements per week. Normal definitions of functional constipation include infrequent bowel movements and hard stools. In contrast, ODS may occur with frequent bowel movements and even with soft stools, and the colonic transit time may be normal, but delayed in the rectum and sigmoid colon.

Descending perineum syndrome refers to a condition where the perineum "balloons" several centimeters below the bony outlet of the pelvis during strain, although this descent may happen without straining. The syndrome was first described in 1966 by Parks et al.

Dyssynergia is any disturbance of muscular coordination, resulting in uncoordinated and abrupt movements. This is also an aspect of ataxia. It is typical for dyssynergic patients to split a movement into several smaller movements. Types of dyssynergia include Ramsay Hunt syndrome type 1, bladder sphincter dyssynergia, and anal sphincter dyssynergia.

In fecal incontinence (FI), surgery may be carried out if conservative measures alone are not sufficient to control symptoms. There are many surgical options described for FI, and they can be considered in 4 general groups.

<span class="mw-page-title-main">Neurogenic bowel dysfunction</span> Human disease involving inability to control defecation

Neurogenic bowel dysfunction (NBD) is the inability to control defecation due to a deterioration of or injury to the nervous system, resulting in faecal incontinence or constipation. It is common in people with spinal cord injury (SCI), multiple sclerosis (MS) or spina bifida.

<span class="mw-page-title-main">Satish SC Rao</span>

Satish Sanku Chander Rao is the J.Harold Harrison Distinguished University Chair in Gastroenterology at the Medical College of Georgia, Augusta University. He served as the former President of the American Neurogastroenterology and Motility Society and as Chair of the American Gastroenterological Association (AGA) Institute Council, Neurogastroenterology/Motility Section.

Low anterior resection syndrome is a complication of lower anterior resection, a type of surgery performed to remove the rectum, typically for rectal cancer. It is characterized by changes to bowel function that affect quality of life, and includes symptoms such as fecal incontinence, incomplete defecation or the sensation of incomplete defecation, changes in stool frequency or consistency, unpredictable bowel function, and painful defecation (dyschezia). Treatment options include symptom management, such as use of enemas, or surgical management, such as creation of a colostomy.

These procedures aim to inject bio-compatible material into the walls of the anal canal, in order to bulk out these tissues. This may bring the walls of the anal canal into tighter contact, raising the resting pressure, creating more of a barrier to the loss of stool, and thereby reducing fecal incontinence. This procedure has many advantages over more invasive surgery, since there are rarely any serious complications.

References

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