Analyzing, and Interpreting HRAM and HDAM Recordings

1. Continue medications

2. Fasting is not necessary

3. Cleaning enema at least 30 min before the test

7.1.2 Patient Preparation

Patients may continue with their routine medications but the medications should be documented to facilitate interpretation of the data. Topical therapy (nifedipine, lidocaine, etc.) must be stopped 1 day before exam, in order not to influence the anal pressure.

Some authors recommended to avoid food since the night before the exam while others allow patients consuming normal meals [9].

Bowel preparation is optional. Many authors do not require it, but the patients are only asked to empty their bowel before the test. If the digital rectal examination, performed immediately before the manometry, reveals that the rectum is loaded with stool, then a 250–500-mL tap water enema is suggested. In this case, at least 30 min should elapse between evacuation of stool and probe placement [10].

Since the presence of feces in rectal ampoule could modify the results, in order to achieve a better standardization of the test, we suggest all patients performing a cleaning enema in the morning of the HRAM/HDAM at least 30 min before the exam.

7.1.3 Patient Position

The test should be conducted in a quiet room in the presence of strictly necessary personnel, in order to create a relaxed and confident relationship with the patient. It is recommended that the patient is placed in the left lateral position with knees and hips bent to 90° angle (Sims position), to guarantee privacy and discretion to the patient [2].

7.1.4 Digital Examination

As reported above, prior to the catheter insertion, a digital rectal examination should be performed using a lubricated gloved finger (any lubricant to aid probe placement should be non-anesthetizing). The presence of tenderness, stool, or blood on the finger glove should be noted [2]. The digital rectal examination is important to teach the patient the maneuvers to be performed during the exam and to test the ability of the subject to understand the commands “squeeze” and “push” [11]. The authors strongly believe that performing a carefully digital rectal examination before anorectal manometry is necessary and positively influence the outcome of the test.

7.1.5 Probe Placement

The probe is calibrated immediately before the procedure by placing it in a calibration chamber, where it is zeroed to atmospheric pressure and set to a range of pressure up to 300 mmHg. All systems require thermal compensation to correct for the pressure drift with time [10]. After calibrating the instrument, the lubricated probe is gently inserted into the rectum with its dorsal side orientated such that the most distal sensor (1 cm level) is located posteriorly at 1 cm from the anal verge. Once positioned, the probe has to be maintained in the same position for the duration of the test. However it is important to continuously monitor it and the operator has to be aware of possible probe movements, especially after the patient performs maneuvers such as squeeze, cough, or bearing down, and eventually to adjust the position of the probe when necessary.

7.1.6 Test Procedure

The exact manometry protocols vary by center. The procedure must include an assessment of rectoanal pressure and anal canal length at rest, the presence of the cough reflex test, the recording of rectoanal pressures during squeeze, simulated evacuation, coughing, and the evaluation of the rectal sensations. A rectal balloon expulsion test, which is an effective screening test to identify defecatory disorders, should be performed at the end of the anorectal manometry [10] (Table 7.2).

Table 7.2

Test procedure

Resting anal pressure: sphincteric length, resting pressure

Cough reflex test

Squeeze pressure and squeeze duration

Push

RAIR rectoanal inhibitory reflex

Rectal compliance

Rectal volume tolerability (first sensation, urge to defecate and discomfort volume)

7.1.6.1 Rest

Resting anal pressures must be measured with the subject relaxed, lying still and not speaking during the examination. There is no agreement how long to wait after inserting the probe before beginning the examination. Several laboratory manuals and guidelines recommend waiting for 5 minutes after inserting the probe before taking. One justification for this is the presence of ultraslow wave activity, which might interfere with the interpretation of the resting pressure [2] (Fig. 7.1).

../images/475577_1_En_7_Chapter/475577_1_En_7_Fig1_HTML.png — Fig. 7.1

Ultraslow waves

However, there is no scientific basis for the duration of the rest period. A prolonged procedure causes discomfort and reduces the patient compliance. In some patients, anorectal manometry can cause pain and discomfort [12]. Dakshitha Praneeth Wickramasinghe et al. analyzing data from 100 consecutive patients who underwent HDAM found that 99% of the patients had their anal canal resting pressure stabilize in <150 s. Therefore a standard ARM assessment can be completed in several minutes. Since there were no significant associations between sex or the age and the time taken for the pressure to stabilize, the waiting time can be recommended for all adult patients, irrespective of their age or sex.

We think that a 1 min wait before starting the recording is sufficient to allow the anal resting pressure to stabilize in the most patients, waiting more time (3 min) only in the presence of ultraslow wave activity. The resting pressure must be recorded at least three times for 1 min, in order to allow a statistically significant average to be carried out.

7.1.6.2 Cough Reflex Test

This maneuver is indicated to assess the integrity of spinal reflex pathways between the rectum and anal canal in patients with incontinence. The patient is asked to cough. Normally, the increased abdominal pressure triggers external sphincter contraction. The maneuver is repeated once more after 10 s [2].

7.1.7 Squeeze

Squeeze pressure is the difference between the maximum voluntary pressure during squeeze contraction and the resting pressure at the same level of the anal canal. The patient is asked to squeeze the anus as long as possible, for a maximum of 30 s, followed by a 30 s rest. Sphincter endurance is the length of time that the patient can maintain a squeeze pressure above the resting pressure.

By convention, this maneuver is performed three times. In the unusual event of poor participant compliance a further attempt is allowed at the practitioner’s discretion.

Ideally rectal pressure should not increase because that would imply that the patient has contracted the abdominal wall [10] (Fig. 7.2).

../images/475577_1_En_7_Chapter/475577_1_En_7_Fig2_HTML.png — Fig. 7.2

Squeeze pressure. Squeeze pressure: the highest pressure during maximal contraction of anal sphincter (white arrow). Squeeze duration: the longest interval, in seconds, between the onset of increase in anal sphincter pressure and when this pressure returned to baseline value (∗)

7.1.8 Simulated Defecation

The patient is asked to bear down as if to defecate. This test is conducted inflating 5 mL of air in the rectal balloon, and pushes down for 30 s and is repeated for three times separated by a 30 s interval. It is essential to instruct patients to not withhold the probe. Indeed, coaching patients while they perform maneuvers might enhance the accuracy of the test. In one study, coaching changed the diagnosis based on manometry from “pathologic” to “normal” values in 14 of 31 patients with incontinence and in 12 of 39 patients with dyssynergic defecation [13] (Fig. 7.3).

../images/475577_1_En_7_Chapter/475577_1_En_7_Fig3_HTML.png — Fig. 7.3

Straining maneuver. Assessment of pressure changes during simulated evacuation. Discoordination of abdominal, rectoanal, and pelvic floor muscles

7.1.9 RAIR (Rectoanal Inhibitory Reflex)

This maneuver examines the integrity of the myenteric plexus between rectum and anal canal. This maneuver consists of intermittent balloon distension in the rectum to assess the relaxation of the internal anal sphincter, while the RAIR can generally be elicited just by a volume of 20 mL of air. Repeating the maneuver for three times, using increasing volumes up to 60–80 mL, it is sufficient to properly assess the presence and the quality of the reflex. If no RAIR is recorded, the following measures may solve the problem: (1) ask the patient not to contract the external anal sphincter during rectal distension, (2) make sure there is no fecal impaction, and (3) increase the rectal distension up to a maximum volume of 250 mL to exclude acquired megarectum [10] (Fig. 7.4).

../images/475577_1_En_7_Chapter/475577_1_En_7_Fig4_HTML.png — Fig. 7.4

RAIR Rectoanal inhibitory reflex. This maneuver examines the integrity of the myenteric plexus between the rectum and anal canal

7.1.10 Rectal Sensation, Graded Balloon Distension

Evaluation of rectal sensation is performed by inflating the balloon placed at the tip of catheter in the rectum. The increasing distension allows to assess the rectal sensation which can be classified as follows:

Sensory threshold: is the minimum rectal volume perceived by the patient.
Urge sensation: is the volume associated with the initial urge to defecate.
Maximum tolerated volume: is the volume at which the patient experiences discomfort and an uncontrollable desire to defecate.

To assess rectal sensation, the rectal balloon is initially distended with air with increments of 10 mL, until the patient reports a first sensation. Thereafter, the balloon is increased in 20 mL steps to a maximum volume of 400 mL. The distension should be ended earlier if the maximum tolerable volume is reached. Each distension is maintained for at least 30 s. Rectal compliance (i.e., pressure-volume relationships) can also be measured during balloon distention but the rectal balloon used for HRAM and HDAM is relatively stiff. For example, when the given HRM catheter balloon is inflated by 50 mL in atmosphere, it has a pressure of 137 mmHg. In theory, rectal compliance can be estimated by subtracting this pressure from the measured balloon pressure during rectal distention. However, in general, rectal compliance measured with an anorectal manometry is not as accurate as measurements obtained with a barostat [10].

7.2 Normal Values for High Resolution Anorectal Manometry

Prior to the introduction of HRM catheters in 2007, anorectal manometry was performed with non-high resolution, water-perfused, or solid-state catheters. Since then HRAM and HDAM catheters are increasingly used in clinical practice, but the long-standing problem of the normality values of traditional ARM is still the biggest problem for a widespread clinical application of this new technique, at least for its use in the study of anorectal pathophysiology.

In addition, anal sphincter pressures at rest and during anal contraction (i.e., squeeze maneuver) recorded with HRAM and conventional ARM are significantly correlated but they tend to be higher when measured with HRAM [14–16]. The rectoanal pressure gradient measured with both techniques was also strongly correlated but the gradient was more negative when evaluated with conventional ARM (−66 mmHg) than with HRAM [16].

Several small studies have evaluated the normal values of HRAM and HDAM [10]. Carrington et al. [11] assess diagnostic accuracy of HRAM in comparison with conventional ARM in terms of discriminating patients with fecal incontinence (FI) vs healthy volunteers (HV). Asymptomatic female volunteers were selected without constipation (Cleveland Clinic Constipation Score, CCCS < 9 [17]) or incontinence (St Marks Incontinence Score, SMIS < 6 [18]), current or previous significant gastrointestinal disease [19], functional gastrointestinal symptoms, previous anal or pelvic surgery, pregnancy or lactation [20], without history of diabetes, cardiovascular, renal, or hepatic disease. In the standard method using (UniTip; UniSensor AG, Attikon, Switzerland) of 12 F external diameter incorporating 12 micro-transducers and using commercially available manometric system (Solar GI HRM v9.1; MMS/Laborie, Enschede, Netherlands) (Table 7.3).

Table 7.3

HR-manometry and 3D-high resolution manometry measures in healthy women and men (from Lee et al. [10], Cross-Adame et al. [9], Carrington et al. [11])

Healthy Women						Healthy Men
	Rest		Squeeze				Rest
	HR-ARM-RP mmHgcm30 s	3DHRAM	HR-ARM-SI mmHg	HR-ARM-SP mmHgcm5 s	3DHRAM		HR-ARM-RP mmHgcm30
Mean	163	76.6	122	368	148	Mean	73
Mean	163	76.6	122	368	148	95%CI	56.5–65.5
Median	151	95.6	112	342	180	Median	46
SD	71	30.3	64	194	72	SD	23
Minimum	67	43	20	45	171	Minimum	94
Maximum	408	86	291	868	190	Maximum	732

HR-ARM-RP high resolution manometry resting pressure, 3DHRAM three dimensional high resolution manometry, HR-ARM-SI high resolution anorectal manometry squeeze increment, HR-ARM-SP high resolution anorectal manometry squeeze pressure

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