Investigation of anorectal motility☆

Chapter 28

Investigation of anorectal motility☆ Victoria Wilkinson-Smitha,b, Guido Basiliscoc, Maura Corsettia,b a

NIHR Nottingham Biomedical Research Centre (BRC), Nottingham University Hospitals NHS Trust and the University of Nottingham, Nottingham, United Kingdom, bNottingham Digestive Diseases Centre, School of Medicine, University of Nottingham, Nottingham, United Kingdom, cFondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico Gastroenterology and Endoscopy Unit, Milano, Italy

Key Points ● ● ●

The anorectum is a complex anatomical and functional organ with multiple functions. Its investigation is therefore difficult with just a single modality, and a multidimensional approach is needed. More research is needed regarding how the results of these tests may impact treatment options.

Introduction The anorectum and pelvic floor are complex structures that control, together with the colon, one’s ability to defecate appropriately. A disorder of some or part of the anatomy or function of the anorectum can result in constipation with disordered defecation, fecal incontinence or a mixture of the two conditions. Studies looking at prevalence of these conditions have found that they affect between 10 to 15% of the population [1, 2].

Anatomy overview Pelvic floor The pelvic floor is a funnel-shaped structure. It attaches to the walls of the lesser pelvis, separating the pelvic cavity from the perineum inferiorly, extending from the pubic symphysis anteriorly to the coccyx within the pelvic sidewalls. It encloses and supports the pelvic viscera (bladder, uterus, and rectum) with two hiatuses: the urogenital hiatus—an anteriorly situated gap, which allows passage of the urethra (and the vagina in females) and the rectal hiatus—a centrally positioned gap, which allows passage of the anal canal. Between the urogenital hiatus and the anal canal lies a fibrous node known as the perineal body, which joins the pelvic floor to the perineum. There is some controversy over the naming and arrangement of the pelvic floor that is mainly composed by the four components of the levator ani (the puborectalis, pubococcygeus, iliococcygeus and coccygeus) and by the fascia coverings/ surrounding connective tissue of the muscles. The puborectalis is a U-shaped sling muscle that is responsible for maintenance of the anorectal angle which helps preserve continence.

Anorectum The rectum is a continuation of the sigmoid colon at the level of the sacrum. It ends in the anal canal, a 2.5–5 cm long canal that is surrounded by the internal and external anal sphincters (IAS and EAS). The IAS is a smooth muscle structure, considered as a continuation of the circular layer of the rectal muscularis propria, innervated by the autonomic nervous system. The EAS is a striated muscle that is innervated voluntarily via the pudendal nerve and it (as well as some of the puborectalis) is an extension of the longitudinal muscles of the rectum.

☆

Will cover the practical approach and interpretation of anorectal manometry, barostat and imaging studies (endoanal ultrasound, barium and MRI defecography).

Clinical and Basic Neurogastroenterology and Motility. https://doi.org/10.1016/B978-0-12-813037-7.00028-5 © 2020 Elsevier Inc. All rights reserved.

399

400  SECTION | B  Clinical approaches to neurogastroenterology

Function: Maintenance of normal defecation Normal defecation and maintenance of continence is a complex process requiring rectal distention by colonic load, the perception of the distension and the discrimination of the nature of the rectal contents and the ability to subsequently propel the stool by relaxing the pelvic floor muscles and anal sphincters in a coordinated sequence of events or to postpone defecation if socially inconvenient [3]. Stool is propelled into rectum from the sigmoid colon by colonic propulsive contractions. Once there, the rectal distension evokes a rectal contraction and the IAS relaxes. This allows rectal contents to contact the epithelial nerve endings in the anal mucosa and lets us know what type of contents are present. Then a conscious decision occurs about how and whether to evacuate the rectal contents. It is at this point that voluntary actions come into play with control of the EAS, so if defecation is inconvenient it can be postponed. On the other hand, if defecation can occur, voluntary initiation of defecation involves both relaxation of pelvic floor muscles (puborectalis and pubococcygeus) and of the EAS so that the pelvic floor descends, and anal canal opens. On top of this, abdominal contractions aid expulsion from rectum and further colonic contractions will push more stool down into the rectum so the entire left colon may be emptied. At the end of this complex process, the subject is more or less satisfied that rectal emptying has occurred.

Disorders of defecation Recent data have shown that whilst traditionally constipation and fecal incontinence (FI) have been considered separately in studies looking at prevalence, they are known to co-occur and a recent Dutch study found this was the case in 3.5% of their population compared to 25% for constipation and 8% for FI [4]. The first steps in the assessment of these disorders is a thorough history and clinical examination that should include digital rectal examination. With regards to history taking, symptoms such as fecal incontinence are not often brought up by the patient in the first instance, so directed questioning can be of benefit [5, 6]. Digital rectal examination should assess first the presence of rectal impaction that is associated with constipation and fecal soiling and that should be treated before further evaluations. When performed by an experienced specialist, digital rectal examination has reasonable accuracy in determining anal pressures when compared to manometry [7, 8]. However it remains underutilized in clinical practice possibly due to variability among physicians in its utilization and in the confidence with its interpretation [9]. Initial treatment of such disorders should focus on diet and lifestyle modification as well as education and basic pharmacological therapy (e.g., laxatives for constipation and correction of diarrhea in patients with fecal incontinence). If this has failed, then a more thorough diagnostic approach might be indicated. Subtyping of patients according to the underlying pathophysiology has been proposed to facilitate their management. However, due to its complex nature, there is no single test that can assess the entire anorectum. In addition, most of the abnormal pathophysiological mechanisms believed to underlie abnormal defecation are non-specifics and are often found also in healthy subjects. Therefore, several different tests and techniques are used in conjunction as part of a diagnostic work-up aimed to identify patients in which a specific treatment might be indicated with a better outcome. However, the cost-benefit of such approach has not yet been demonstrated. The commonly used techniques in the work-up of patients with disordered defecation will be discussed in this chapter.

Investigations Anorectal manometry Manometry describes the use of pressure sensors, mounted on a catheter or probe, that are inserted into a part of the bowel to allow data to be collected on the changing pressures inside the lumen over a period of time. Since 2008, high resolution and high definition manometry (HR-ARM/HD-ARM) have been used to assess the sensorimotor function of the anorectum. These catheters have more sensors than the traditional non-high-resolution catheters (which had three or six unidirectional sensors) and allow a more thorough assessment of the desired area. Whilst both techniques are still used in clinical practice, HR-ARM is becoming more widely adopted, especially in the more specialized centers [10]. During studies of the anorectum, patients are asked to perform maneuvers such as squeeze, cough, and simulated evacuation whilst the catheter is in place, allowing for assessment of the pressures in several dynamic conditions that are largely influenced by the voluntary control of the activity of the striated muscles. At present, the methods and analysis of ARM vary widely between centers [10]. This represents a strong limitation to the widespread utilization of the anorectal manometry in clinical practice, mainly because the normal values are expected to vary depending on the technique and catheter used. A recent consensus group has proposed a standardized protocol that would improve the reproducibility of the technique going forward (Fig. 1) [11].



Investigation of anorectal motility Chapter | 28  401

FIG. 1  Standardized protocol for high-resolution anorectal manometry. (Adapted from Carrington EV, Scott SM, Bharucha A, Mion F, Remes-Troche JM, Malcolm A, et al. Expert consensus document: advances in the evaluation of anorectal function. Nat Rev Gastroenterol Hepatol 2018;15(5):309–23.)

Normal values and interpretation A significant challenge in the interpretation of the ARM tracings is the lack of definitive normal ranges using standard methodology. Several have been reported in several studies and are summarized in Tables 1 and 2. Resting pressure Resting anal pressure is mainly maintained by the IAS but also the EAS and hemorrhoidal plexus may play a role [3]. The resting anal pressure is assessed, as recommended in the standardized protocol, at the beginning of the study, after the catheter has been inserted and left in place for at least 3 min (this allows any reflex contractions in response to the insertion to subside). The resting pressure is then recorded over a period of up to 60 s [16]. This is probably too short a time to catch the influence of the ultraslow wave cycling activity and to assess the presence of spontaneous transient relaxations of the IAS that might theoretically increase the risk of fecal incontinence. Increased/decreased resting pressure An increased resting anal pressure often occurs in patients with fissure or pain as it suggests there is muscle spasm [18]. A decreased resting anal pressure is a common finding in injury or degeneration of the IAS. Squeeze pressure A series of voluntary squeezes (see Fig. 1) are performed to assess the voluntary contraction of the EAS. A decreased pressure in terms of a reduced maximal squeeze pressure and of the inability to maintain a prolonged squeeze may be due

TABLE 1  Normal values of high-resolution and high-definition anorectal manometry in women Authors

Noelting et al. [12]

Noelting et al. [12]

Li et al. [13]

Lee et al. [14]

Carrington et al. [15]

Coss-Adame et al. [16]

Mion et al. [17]

Year

2012

2012

2013

2014

2014

2015

2017

Gender

F (n=30, <50 years)

F (n=32, ≥50 years)

F (n = 46)

F (n = 27)

F (n = 96)

F (n = 42)

F (n = 36)

Ethnicity

Western

Western

Asian

Asian

Western

Western

Western

Method

HR-ARM

HR-ARM

HD-ARM

HR-ARM

HR-ARM

HD-ARM

3D-ARM

Manufacturer

Given

Given

Given

Sandhill

MMS

Given

Medtronic

Variables

Mean ± SEM

10th, 90th percentile

Mean ± SEM

10th, 90th percentile

Mean ± SEM

95% CI

Median

Maximum resting pressure

88 ± 3

68, 122

63 ± 5

33, 91

68.5 ± 2.4

63.6–73.4

Not reported

Mean resting pressure

Not reported

60.2 ± 2.2

55.8–64.6

32

24–42

65 ± 19

25, 111

Maximum squeeze pressure

167 ± 6

115, 209

162 ± 12

99, 248

167.4 ± 8.4

150.5–184.3

75

61–89

225 ± 89

HPZ length (cm)

3.6 ± 0.1

2.8, 4.4

3.5 ± 0.2

2.4, 4.5

3.5 ± 0.1

3.3–3.7

Not reported

Duration of sustained squeeze (s)

12 ± 1

3, 23

14 ± 3

3, 23

14.7 ± 0.8

13.2–16.3

Not reported

Anal squeeze increment

73 ± 6

23, 113

96 ± 12

28, 171

Not reported

Residual anal pressure

63 ± 5

35, 97

32 ± 5

3, 94

65.2 ± 6.7

Anal relaxation rate (%)

32 ± 5

7, 65

25 ± 10

−68, 91

27.2 ± 2.9

Not reported

IQR

Mean

95% CI

Mean

95% CI

76

71–81

83

75–90

Not reported

74

68–81

76, 503

205

186–224

180

163–198

3.5 ± 0.8

1.6, 6

4

3.8–4.2

3.5a

3.3–3.7

11 ± 9

2, 30

28

27–30

Not reported

Mean ± SD

Min, Max

Not reported

20

12–28

113 ± 62

20, 281

Not reported

Not reported

51.8–78.7

19

10–35

43 ± 21

12, 110

36

Not reported

21.2–33.0

30

0–75

24 ± 22

0, 83

Not reported

28–43

Not reported

Intrarectal pressure

20 ± 3

0.7, 47

32 ± 5

5, 72

45.8 ± 7.2

31.2–60.4

37

27–51

64 ± 31

Rectoanal pressure differential

−41 ± 6

−74, −1

−12.6 ± 6

−55, 32

−12.8± 8.5

−29.8–4.1

16

5–30

Not reported

Not reported

Not reported

First sensation (mL)

33 ± 2

20, 40

32 ± 2

20, 40

40 ± 1.8

36.3–43.6

10

10–20

Not reported

24

21–26

25a

Desire to defecate (mL)

56 ± 3

40, 75

59 ± 4

40, 90

Not reported

60

50–70

Not reported

88

79–96

Not reported

Urge to defecate (mL)

86 ± 5

60, 120

96 ± 5

60, 120

92.6 ± 4.4

82.2–98.6

115

98–153

Not reported

139

130–147

101a

83–119

Discomfort (mL)

Not reported

145 ± 5.2

134.6–155.4

Not reported

Not reported

193

182–204

211a

190–231

Balloon expulsion time

31 ± 10

Not reported

Not reported

a

Not reported 4, 75

17 ± 9

3, 15

Not reported

15

10–30

18, 200

39

34–45

Not reported

20–31

Not reported

This study reported these outcomes with combined male and female data. HPZ, high pressure zone; F, female; HR-ARM, high-resolution anorectal manometry; HD-ARM, high-definition anorectal manometry; 3D-ARM, 3D-high definition anorectal manometry; SEM, standard error of the mean; SD, standard deviation; IQR, interquartile range; Min, minimum; Max, maximum; CI, confidence interval. Adapted from Lee TH, Bharucha AE. How to perform and interpret a high-resolution anorectal manometry test. J Neurogastroenterol Motil 2016;22(1):46–59; Mion F, Garros A, Brochard C, Vitton V, Ropert A, Bouvier M, et al. 3D high-definition anorectal manometry: values obtained in asymptomatic volunteers, fecal incontinence and chronic constipation. Results of a prospective multicenter study (NOMAD). Neurogastroenterol Motil 2017;29(8):e13049.

Authors

Li et al. [13]

Lee et al. [14]

Carrington et al. [15]

Coss-Adame et al. [16]

Mion et al. [17]

Years

2013

2014

2014

2015

2017

Gender

M (n = 64)

M (n=27)

M (n=19)

M(n=36)

M (n=10)

Ethnic

Asian

Asian

Western

Western

Western

Method

HD-ARM

HR-ARM

HR-ARM

HD-ARM

3D-ARM

Manufacturer

Given

Sandhill

MMS

Given

Medtronic

Variables

Mean ± SEM

95% CI

Median

Maximum resting pressure

69.5 ± 2.2

65.2–73.8

Not reported

Mean resting pressure

61.3 ± 2.1

56.5–65.5

46

39–56

73 ± 23

38, 136

Not reported

Maximum squeeze pressure

194.8 ± 6.9

180.9–208.6

178

140–212

290 ± 155

94, 732

266

HPZ length (cm)

3.6 ± 0.1

3.4–3.8

Not reported

3.9 ± 0.8

2.4, 5.3

Duration of sustained squeeze (s)

12.3 ± 0.7

10.8–13.8

Not reported

16 ± 11

Anal squeeze increment

Not reported

Residual anal pressure

81.2 ± 4.3

Anal relaxation rate (%)

IQR

Mean ± SD

Min, Max

Mean

95% CI

Mean

95% CI

90

83–96

89

74–103

77

65–90

245–287

273

239–308

4.3

4.1–4.5

3.5a

3.3–3.7

3, 30

30

28–30

Not reported

Not reported

55

41–77

144 ± 116

40, 474

Not reported

72.6–89.7

26

13–55

57 ± 23

20,104

40

22.5 ± 2.9

16.6–28.3

16

0–82

16 ± 33

0, 60

Not reported

Intrarectal pressure

72.3 ± 9.4

53.5–91.2

69

44–98

71 ± 33

20, 140

43

Rectoanal pressure differential

−13.4 ± 7.5

−28.5–1.7

30

5–66

Not reported

Not reported

First sensation (mL)

44.2 ± 1.8

40.6–47.8

10

10–20

Not reported

22

20–25

25a

Desire to defecate (mL)

Not reported

80

60–120

Not reported

94

82–103

Not reported

Urge to defecate (mL)

102.5 ± 4.1

130

110–178

Not reported

163

140–167

101a

192–222

a

Discomfort (mL)

154.5 ± 3.7

Balloon expulsion time

Not reported

a

94.2–110.8 147.1–162

Not reported 15

5–50

Not reported

206

Not reported

Not reported

Not reported 28–52

Not reported Not reported

35–51

Not reported Not reported 20–31

211

83–119 190–231

Not reported

This study reported these outcomes with combined male and female data. HPZ, high pressure zone; M, male; HR-ARM, high-resolution anorectal manometry; HD-ARM, high-definition anorectal manometry; 3D-ARM, 3D-high definition anorectal manometry; SEM, standard error of the mean; SD, standard deviation; IQR, interquartile range; Min, minimum; Max, maximum; CI, confidence interval. Adapted from Lee TH, Bharucha AE. How to perform and interpret a high-resolution anorectal manometry test. J Neurogastroenterol Motil 2016;22(1):46–59; Mion F, Garros A, Brochard C, Vitton V, Ropert A, Bouvier M, et al. 3D high-definition anorectal manometry: values obtained in asymptomatic volunteers, fecal incontinence and chronic constipation. Results of a prospective multicenter study (NOMAD). Neurogastroenterol Motil 2017;29(8):e13049.

404  SECTION | B  Clinical approaches to neurogastroenterology

TABLE 2  Normal values of high-resolution and high-definition anorectal manometry in men

Investigation of anorectal motility Chapter | 28  405



to ­patient noncompliance or genuine weakness of the sphincter due to injury of either muscle or nerve [18]. Decreased squeeze pressure measured with HR-ARM can distinguish between healthy and incontinent women [19]. Cough reflex An increase in intra-abdominal pressure, as is induced by coughing, should cause contraction of the EAS via the sacral reflex arc [20]. Decreased squeeze pressure and a normal cough reflex may reflect impaired voluntary control of the EAS and/or damage above the sacral level of the spinal cord. In contrast, a decreased squeeze pressure and an abnormal cough reflex suggest an injury below the sacral level (e.g., Cauda equina). Response to straining Patients are asked to simulate evacuation by bearing down (as if to expel the catheter) [20]. This technique has some limitations due to variations in positioning (on-bed or on-commode), type of catheter/balloon and the patients’ participation due to possible embarrassment. Moreover, a recent study has demonstrated that 90% of the healthy subjects, when requested to bear down, presented with the same manometry pattern previously considered pathological. Despite some abnormal manometric patterns are more frequent in patients than in healthy controls the diagnostic performances of the test suggest that its clinical utility in the diagnostic work-up of chronic constipation merits further analysis. Balloon expulsion test This test is performed by asking the patient to expel a rectal balloon inflated with air or water [20] at a fixed volume or at the volume inducing desire to defecate, while sitting on a commode or lying in lateral position. It should be noted though that also this test has not yet been standardized and different centers applies different methods (water vs air, commode vs lateral position) and analysis criteria (1 min vs 2 min vs 5 min threshold). The balloon expulsion test has been found to be useful in identifying patients responding to biofeedback in comparison to patients with slow transit constipation. On the other hand, biofeedback has been shown to be useful also in patients with normal balloon expulsion test. Recto-anal inhibitory reflex (RAIR) The RAIR identifies an intrinsic reflex, when the IAS relaxes in response to rapid distention of the rectum. This may be absent in disorders such as Hirschsprung disease [21] and in rare patients with acquired myenteric neuropathies or after lower anterior resection. Rectal sensation Assessment of the rectal sensitivity to distention is performed as part of the ARM protocol. It is performed using an elastic balloon attached to the manometry catheter which is inflated in the rectum in stepwise fashion. The patient is then asked to report when they first feel a sensation of the balloon, then when they feel a desire to defecate, when this then becomes an urgent sensation and up to the maximum tolerable distention [20]. The volumes are then recorded at each of these thresholds. A reduced volume threshold for sensations (rectal hypersensitivity) is often seen in patients with disorders such as irritable bowel syndrome [22] and proctitis, whereas an increased volume threshold for sensations (rectal hyposensitivity) is associated with constipation [23] and also evacuation disorders related to spinal injury [24]. Rectal sensations are affected by the motor response of rectum to distension. The shape and stiffness of the distending balloon as well as the type (pressure vs volume) and rate of distension influence the assessment of the rectal motor response to distension and the sensory thresholds. Accordingly, the rectal motor responses to distension and volume-pressure thresholds for sensation cannot be reliably measured with the rectal balloons commonly used during ARM but should instead be measured with a barostat or with a standardized manual distension of an infinitely compliant bag.

Practical tips for ARM interpretation ●

●

Alteration in resting pressures? ● Think about an abnormal IAS Alteration in squeeze? ● Think about an abnormal EAS. This measure is also influenced by the attitude of the subject to accomplish the task.

406  SECTION | B  Clinical approaches to neurogastroenterology

●

●

●

●

●

Abnormal cough? ● Is the squeeze NORMAL? ➔Possible lesion above the sacral level ● Is the squeeze ABNORMAL ➔Possible lesion below the sacral level Impaired RAIR? ● Think Hirschsprung’s or Myenteric Neuropathies Response to straining ● Overlaps with healthy subjects Balloon Expulsion Test ● Predictive of response to biofeedback Rectal sensation ● The results are influenced by the technique used to distend the rectum and can only suggest the possible presence of hypoor hyper-sensitivity to distension

Barostat The barostat has been used in research settings to study gut tone and the sensory and motor responses to distention in rectum, colon and stomach since its development by Malagelada and Azpiroz in 1987 [25]. Muscle tone refers to the tonic state of contraction of smooth muscle, whereas compliance refers to the resistance of active (muscle contraction) and passive (connective tissue) forces to distension. The active component plays a major role at low volumes of distension whereas the passive component mainly activated close to the maximum capacity of the viscus. Muscle tone is not static but varies at different distending volumes. The relevance of the active smooth muscle tone can be assessed by the administration of drugs that abolish muscle tone such as glucagon or anti-cholinergic agents. Physiological influences on smooth muscle tone in the rectum and colon include eating and sleep. Muscle tone is usually measured at minimal distending pressures whereas compliance is measured over a wide range of distending pressures. Intermittent distension also measures rectal sensation [20, 26]. The barostat device uses feedback circuitry to keep the pressure in a distending balloon constant by either pumping air into or withdrawing air from the balloon. The measure of muscle tone is the average volume of air in the bag over an extended period, e.g., 15 min. Compliance is measured as the pressure-volume relationship at several different distending pressures. Alterations in rectal compliance may result in decreased or increased rectal capacity, impaired ability to perceive rectal distention, and altered threshold of reflexive IAS inhibition by rectal distention. Physiological factors that decrease compliance include inflammation, fibrosis, surgical operations and drugs. At present, measurement of rectal compliance and sensation is of clinical value in identifying rectal disorders [20, 26].

Imaging studies Endoanal ultrasound Endoanal ultrasound assesses the anatomy of anal sphincters. It is primarily performed to investigate fecal incontinence as well as anal pain, anal sepsis and malignancy [27]. Cross-sectional images of the anal sphincters are obtained using a mechanically rotated probe that produces 360° crosssectional images at different levels of the sphincter. Computerized equipment allows the 3-D reconstruction of these images. 10 MHz transducers are usually used, but lower frequencies can be used to assess deeper layers and higher frequencies to assess the details close to the probe. Three layers are usually observed: firstly, the sub-epithelial or submucosal layer, a moderately reflective layer adjacent to the well-defined ring of high reflectivity of the plastic cone of the probe. Secondly, the IAS appearing as an evident hypoechoic ring immediately close to the sub-epithelial/submucosal layer. Thirdly, the longitudinal layer and the EAS that can appear as a single hyperechoic layer or as two distinct layers, the inner of which is more hypoechoic. The normal cross-sectional images differ according to the cranio-caudal level of the section. Orientation of the reported images are as those of a CT scan (top of the image is the anterior of the patient and left of the image is the right side of the patient). The normal appearance of the anal canal at the more cranial level is characterized by the posterior mixedhyperechoic sling of the puborectalis muscle. (Fig. 2). The normal appearance of the mid anal canal in male often shows four distinct layers: the submucosal, the hypoechoic IAS, the hyperechoic longitudinal muscle and the hypoechoic EAS (Fig. 3). In women the EAS is hyperechoic and indistinguishable from the inner longitudinal muscle. The outer border of the EAS is also difficult to be clearly recognized (Fig. 4). At the caudal level of the anal canal the IAS terminates, and the EAS appears as an almond-like mixed-hyperechoic layer. Hemorrhoids appear as a hypoechoic focus close to the high reflectivity of the plastic cone of the probe (Fig. 5).



Investigation of anorectal motility Chapter | 28  407

FIG. 2  Normal sphincter appearance at the cranial level of the anal canal. Note the posterior hyperechoic sling of the puborectalis.

FIG. 3  Normal appearance of the mid-anal canal in an adult male. Note the hyperechoic longitudinal muscle and the hypoechoic external anal sphincter.

FIG. 4  Normal appearance of the mid-anal canal in an adult female. Note the hyperechoic external anal sphincter that is indistinguishable from the longitudinal muscle.

408  SECTION | B  Clinical approaches to neurogastroenterology

FIG. 5  Normal appearance at the caudal level of the anal canal. Note the posterior hypoechoic area close to the probe corresponding to a posterior hemorrhoid.

The thickness of the IAS can be measured with precision whereas the external border of the EAS is often difficult to be defined, making the thickness of the EAS a poorly reproducible measure. Normal IAS thickness is 1.8 ± 0.5mm, greater in male and those older than 55 years. Normal EAS thickness is 7.1 ± 0.7 mm. Pathology with circular muscle integrity A marked thickening (>3.5 mm) of the IAS is seen in patients with solitary rectal ulcer syndrome and in the rare patients with hereditary proctalgia fugax. In these rare cases high amplitude ultra-slow waves are recorded at manometry. Thinning of the IAS (<1 mm) is observed in the rare incontinent patients with primary degeneration of the internal anal sphincter and in some patients with scleroderma. Resting anal pressure is reduced at manometry. Pathology with loss of circular muscle integrity Integrity of the sphincters can be disrupted following obstetric trauma, fistula and surgical sphincterotomy. In these conditions anal ultrasound demonstrates the circular and longitudinal extension of the sphincter discontinuity. Fig. 6 shows a trans-sphincteric fistula. A hypoechoic collection with few hyperechoic bubbles starts from the submucosal layer of the mid anal canal at 2 o clock and cross the internal and external anal sphincters spreading for 30° in the longitudinal muscle layer (Fig. 6, arrow).

FIG. 6  Trans-sphincteric fistula at the mid anal canal section. At 2 o’clock note the hypoechoic area that starts from the submucosal layer and crosses the internal and external anal sphincter.

Investigation of anorectal motility Chapter | 28  409



Defects of circular muscle integrity in the anterior quadrant at the cranial level of the sphincter are difficult to be identified due to the complex and heterogeneous echogenic anatomy of the area. The impact of sphincter disruptions on anal continence is variable and can be quantified at manometry. Practical tips for endoanal ultrasound interpretation ●

●

● ●

●

●

Endoanal ultrasound is the simplest, more reliable and less invasive test to assess the anatomic defects of the internal and external anal sphincter. Assess the sphincter at the different levels at least twice: the first to detect the abnormality and the second to reproduce the finding and take a representative image. Change the frequency of the probe, the magnification and the gray scale to highlight the detected abnormality. Measure the greatest thickness of the internal anal sphincter in patients with fecal incontinence and in patients with difficult defecation or with anal pain and an apparently thick muscle. In the learning phase, discuss the major findings with a colleague during the exam and check the most relevant results with another technique or with the surgeon when possible. Remember that endoanal ultrasound is complementary to MRI in the assessment of anal sphincter anatomy. In particular, a dedicated MRI is superior to endoanal ultrasound: ● In the definition of the thickness of the external anal sphincter. ● In the assessment of the extension of the inflammation cranial to the puborectalis plane.

Defecography Defecography or defecating proctography is the use of dynamic imaging techniques to visualize and assess a patients’ ability to expel contents from the rectum. It is commonly performed using X-ray (fluoroscopy) however more recently techniques using magnetic resonance imaging (MRI) have been developed. Indication for this type of investigations are based on the suspicion that structural abnormalities (rectocele, enterocele, or intussusception/rectal prolapse) or functional abnormalities (poor opening of the anorectal angle by non-relaxing or contracting puborectalis during attempted defecation, poor anal sphincter relaxation, incomplete or prolonged evacuation of rectal content) might impede evacuation and be the cause of defecatory symptoms in at least some patients with chronic constipation. Barium defecography using fluoroscopy After preparation of the bowel and rectum (+/− vagina in females) with barium, images and video are taken using the fluoroscope at a variety of positions during both rest and during maneuvers such as squeezing before being asked to empty the rectum. During the act of defecation, the patient is seated on a commode to mimic the physiological process as close as possible. MRI MRI defecography has been more recently adopted as an alternative to fluoroscopy as it can provide similar information without exposure to ionizing radiation. This allows more detailed information about the anatomy, however, it is performed supine (although there are a few reported cases of upright scanners being used in early research [28–30]). This position makes the test less physiological and might explain why MRI defecography underestimates certain pathologies such as intussusceptions [31] and overestimates functional abnormalities compared with barium defecography. Normal defecography Normal emptying of the rectum should occur within 30 s. The urge to evacuate the rectum is initiated by the distention due to the inserted barium. Abdominal straining and voluntary pelvic floor relaxation should open the anal canal and allow passage of rectal contents. Defecation is accompanied by the dynamic descent of the pelvic floor and the widening of the anorectal angle. Once the straining has ceased and the evacuation is complete, the anal canal closes, and the anorectal angle becomes more acute with the structures returning to their resting position. Abnormal findings Several underlying static and dynamic abnormalities have been considered to cause difficulty with defecation: Dyssynergic defecation:  This refers to the poor opening of the anorectal angle by a non-relaxing or paradoxically contracting puborectalis and/or external anal sphincter during attempted defecation.

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Rectocele  This is a protrusion of the rectal wall (usually anterior) through the vaginal wall that occurs during defecation. This is due to weakening of the rectovaginal septum. Enterocele  This is protrusion of the small bowel into the rectovaginal space or into the vagina itself. It usually becomes evident at the end of evacuation and after complete voiding. Intussusception/rectal prolapse  Intussusception is the infolding of rectal mucosa, and if this then protrudes down below the anal verge it becomes a rectal prolapse. Descending perineum syndrome  This is pathological descent of the pelvic floor at rest or during straining, usually due to chronic straining and stretching of elastic tissue in the fascia. This can involve all the pelvic floor or just the anorectum. Clinical considerations Defecography still has several clinical limitations (1) The techniques used to perform defecography and the definition of the abnormalities vary widely. (2) The agreement between independent observers in the detection of some of these abnormalities is poor. (3) The presence of structural and functional abnormalities is not closely correlated with rectal emptying. (4) Both functional and even large structural abnormalities are not always correlated with symptoms. (5) There is a considerable overlap between asymptomatic healthy subjects and constipated patients in some of the findings considered to be responsible of difficult defecation particularly for small (<4 cm) rectoceles and internal prolapse. (6) The number of patients studied for normative values remains small. On the other hand, both structural and functional abnormalities were reported more often in patients with difficult defecation than in healthy subjects suggesting they may explain, at least in part, the symptoms. It is important to remember that the detection of structural abnormalities in constipated patients is often followed by surgical attempt to correct such abnormalities. The results of these surgical approaches were recently reviewed [32–34]. The quality of data of the study was poor (level IV evidence). Both rectal excision and rectal suspension procedures seemed to have an excellent outcome: the proportion of patients improving on a global satisfaction rating was high (72–83%) in the short term however with a non-negligible percentage of side effects, such as mesh complications after rectopexy and chronic pain and urgency after stapler trans-anal rectal resection, ranging from 6% to 21%. In this evaluation it should be considered that efficacy data for colectomy in patients with slow transit constipation were even greater in the short term (86%) but then the poor functional outcomes that emerged in the long term indicated extreme caution for this surgical approach [35]. Moreover, the pathophysiology of constipation is multifactorial with co-existing dietary, colonic, rectal, behavioral and psychological abnormalities. In this context, patients’ dissatisfaction for treatments has a multidimensional and heterogeneous construct and may be reported even in presence of normal evacuation [36]. Accordingly, although defecography may disclose more anatomical abnormalities in patients with difficult defecation than in healthy subjects, to establish a causal relationship between these abnormalities and patients’ symptoms remains still an unmet need. Before the routine use of this technique in clinical practice, high quality randomized controlled study or prospective cohort studies should demonstrate that patients with chronic constipation undergoing standardized defecography and surgical repair of well-defined anatomical abnormalities have a better long-term outcome than patients undergoing a more conservative treatment.

Conclusions The pelvic floor and anorectum is a complex structure whose function requires complex interplay of several motor and sensory aspects that requires a multi-modality assessment. The understanding of the relationship between anatomical, motor and sensory abnormalities and symptoms associated with the act of defecation remains challenging.



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References [1] Bharucha AE, Zinsmeister AR, Locke GR, Seide BM, McKeon K, Schleck CD, et al. Prevalence and burden of fecal incontinence: a populationbased study in women. Gastroenterology 2005;129(1):42–9. [2] Locke 3rd GR, Pemberton JH, Phillips SF. AGA technical review on constipation. Gastroenterology 2000;119(6):1766–78. [3] Bharucha AE. Pelvic floor: anatomy and function. Neurogastroenterol Motil 2006;18(7):507–19. [4] Meinds RJ, van Meegdenburg MM, Trzpis M, Broens PMAA. On the prevalence of constipation and fecal incontinence, and their co-occurrence, in the Netherlands. Int J Colorectal Dis 2017;32(4):475–83. [5] Bartlett L, Nowak M, Ho YH. Reasons for non-disclosure of faecal incontinence: a comparison between two survey methods. Tech Coloproctol 2007;11(3):251–7. [6] Peden-Mcalpine C, Bliss D, Hill J. The experience of community-living women managing fecal incontinence. West J Nurs Res 2008;30:817–35. [7] Orkin BA, Sinykin SB, Lloyd PC. The digital rectal examination scoring system (DRESS). Dis Colon Rectum 2010;53(12):1656–60. [8] Tantiphlachiva K, Rao P, Attaluri A, Rao SSC. Digital rectal examination is a useful tool for identifying patients with dyssynergia. Clin Gastroenterol Hepatol 2010;8(11):955–60. [9] Wong RK, Drossman DA, Bharucha AE, Rao SS, Wald A, Morris CB, et al. The digital rectal examination: a multicenter survey of physicians’ and students’ perceptions and practice patterns. Am J Gastroenterol 2012;107(8):1157–63. [10] Carrington EV, Heinrich H, Knowles CH, Rao SS, Fox M, Scott SM. Methods of anorectal manometry vary widely in clinical practice: results from an international survey. Neurogastroenterol Motil 2017;29(8):e13016. Relevent article underlying the lack of standardization of the anorectal manometry across different centres. [11] Carrington EV, Scott SM, Bharucha A, Mion F, Remes-Troche JM, Malcolm A, et al. Expert consensus document: advances in the evaluation of anorectal function. Nat Rev Gastroenterol Hepatol 2018;15(5):309–23. [12] Noelting J, Ratuapli SK, Bharucha AE, Harvey DM, Ravi K, Zinsmeister AR. Normal values for high-resolution anorectal manometry in healthy women: effects of age and significance of rectoanal gradient. Am J Gastroenterol 2012;107(10):1530–6. [13] Li Y, Yang X, Xu C, Zhang Y, Zhang X. Normal values and pressure morphology for three-dimensional high-resolution anorectal manometry of asymptomatic adults: a study in 110 subjects. Int J Colorectal Dis 2013;28(8):1161–8. [14] Lee HJ, Jung KW, Han S, Kim JW, Park S-K, Yoon IJ, et al. Normal values for high-resolution anorectal manometry/topography in a healthy Korean population and the effects of gender and body mass index. Neurogastroenterol Motil 2014;26(4):529–37. [15] Carrington EV, Brokjaer A, Craven H, Zarate N, Horrocks EJ, Palit S, et al. Traditional measures of normal anal sphincter function using highresolution anorectal manometry (HRAM) in 115 healthy volunteers. Neurogastroenterol Motil 2014;26(5):625–35. [16] Coss-Adame E, Rao SSC, Valestin J, Ali-Azamar A, Remes-Troche JM. Accuracy and reproducibility of high-definition anorectal manometry and pressure topography analyses in healthy subjects. Clin Gastroenterol Hepatol 2015;13(6):1143–1150.e1. [17] Mion F, Garros A, Brochard C, Vitton V, Ropert A, Bouvier M, et al. 3D high-definition anorectal manometry: values obtained in asymptomatic volunteers, fecal incontinence and chronic constipation. Results of a prospective multicenter study (NOMAD). Neurogastroenterol Motil 2017;29(8):e13049. [18] Lee TH, Bharucha AE. How to perform and interpret a high-resolution anorectal manometry test. J Neurogastroenterol Motil 2016;22(1):46–59. [19] Ratuapli SK, Bharucha AE, Noelting J, Harvey DM, Zinsmeister AR. Phenotypic identification and classification of functional defecatory disorders using high-resolution anorectal manometry. Gastroenterology 2013;144(2):314–322.e2. [20] de Lorijn F, Kremer LCM, Reitsma JB, Benninga MA. Diagnostic tests in Hirschsprung disease: a systematic review. J Pediatr Gastroenterol Nutr 2006;42(5):496–505. [21] Simrén M, Törnblom H, Palsson OS, van Tilburg MAL, Van Oudenhove L, Tack J, et al. Visceral hypersensitivity is associated with GI symptom severity in functional GI disorders: consistent findings from five different patient cohorts. Gut 2018;67(2):255–62. [22] Gladman MA, Lunniss PJ, Scott SM, Swash M. Rectal hyposensitivity. Am J Gastroenterol 2006;101(5):1140–51. [23] Burgell RE, Scott SM. Rectal hyposensitivity. J Neurogastroenterol Motil 2012;18(4):373–84. [24] Azpiroz  F, Malagelada  J-R. Gastric tone measured by an electronic barostat in health arid postsurgical gastroparesis. Gastroenterology 1987;92(4):934–43. [25] Scott SM, Van den Berg MM, Benninga MA. Rectal sensorimotor dysfunction in constipation. Best Pract Res Clin Gastroenterol 2011;25(1):103–118. [26] Youssef AT. Use of ultrasonography in clarifying the etiology of anal pain. J Med Ultrasound 2017;25(4):208–14. [27] Bertschinger KM, Hetzer FH, Roos JE, Treiber K, Marincek B, Hilfiker PR. Dynamic MR imaging of the pelvic floor performed with patient sitting in an open-magnet unit versus with patient supine in a closed-magnet unit. Radiology 2002;223(2):501–8. [28] Schoenenberger  AW, Debatin  JF, Guldenschuh  I, Hany  TF, Steiner  P, Krestin  GP. Dynamic MR defecography with a superconducting, ­open-configuration MR system. Radiology 1998;206(3):641–6. [29] Iacobellis F, Brillantino A, Renzi A, Monaco L, Serra N, Feragalli B, et al. MR imaging in diagnosis of pelvic floor descent: supine versus sitting position. Gastroenterol Res Pract 2016. Epub 2016 Jan 12. [30] Ramage L, Simillis C, Yen C, Lutterodt C, Qiu S, Tan E, et al. Magnetic resonance defecography versus clinical examination and fluoroscopy: a systematic review and meta-analysis. Tech Coloproctol 2017;21(12):915–27. [31] Knowles CH, Grossi U, Horrocks EJ, Pares D, Vollebregt PF, Chapman M, et al. Surgery for constipation: systematic review and practice recommendations: graded practice and future research recommendations. Colorectal Dis 2017;19(Suppl. 3):101–13. [32] Grossi U, Knowles CH, Mason J, Lacy-Colson J, Brown SR. Group NC working, et al. surgery for constipation: systematic review and practice recommendations: results II: hitching procedures for the rectum (rectal suspension). Colorectal Dis 2017;19(Suppl. 3):37–48.

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[33] Mercer-Jones M, Grossi U, Pares D, Vollebregt PF, Mason J, Knowles CH, et al. Surgery for constipation: systematic review and practice recommendations: results III: rectal wall excisional procedures (rectal excision). Colorectal Dis 2017;19(Suppl. 3):49–72. [34] Knowles CH, Grossi U, Chapman M, Mason J, NIHR CapaCITY Working Group, Pelvic Floor Society. Surgery for constipation: systematic review and practice recommendations: results I: colonic resection. 2017/09/30. Colorectal Dis 2017;19(Suppl. 3):17–36. [35] Neri  L, Conway  PM, Basilisco  G, Laxative Inadequate Relief Survey (LIRS) Group. Confirmatory factor analysis of the patient assessment of constipation-symptoms (PAC-SYM) among patients with chronic constipation. Qual Life Res 2015;24(7):1597–605.