9. Atlas

Fig. 9.1

Resting pressure

During the analysis of resting pressure mean pressure, length of the HPZ and simmetry has to be evaluated.

9.2 Squeeze

The contractile activity of the external anal sphincter muscle is evaluated by asking the patient to perform three consecutive maximal anal contractions of 5 seconds each (short squeeze, Fig. 9.2a) and one 30 seconds long squeeze (endurance squeeze, Fig. 9.2b).

The voluntary contraction maneuver causes a pressure increase on the high resolution manometric color-contour plot with warm colors appearence (in Fig. 9.2, peak pressure 356.0 mmHg, arrow 1).

../images/475577_1_En_9_Chapter/475577_1_En_9_Fig2_HTML.png — Fig. 9.2

(a) Short squeeze, (b) Endurance squeeze

On 3D high definition image the squeezing maneuver generates an hourglass shape appearance (Fig. 9.2, arrow 2): it is possible to appreciate a central pressure peak that causes the total or sub-total obliteration of the anal canal, bounded by two low pressure zones, proximally and distally.

The 3D image also allows to detect asymmetry of the external anal sphincter contraction (for example, asymmetry due to traumatic or iatrogenic damage), otherwise not detectable through simple 2D high resolution evaluation.

9.3 Push

In physiological conditions, the pushing maneuver leads to an increase of the abdominal pressure (as a consequence of the bearing down maneuver) associated with anal canal relaxation. The simulated defecation is repeated at least three times with the patient lying on his left side.

On the high resolution color-contour, it is possible to appreciate a shift towards colder colors (Fig. 9.3, arrow 1) on the sphincter apparatus corresponding to physiological sphincterial relaxation (in Fig. 9.3, relaxing pressure: 37.4 mmHg); on the rectal sensor color-contour (arrow 2), it is necessary to verify the effective pressure increase testifying that an adequate bearing down maneuver is performed by the patient: rectal pressure increase is efficient when it exceeds at least 40 mmHg.

../images/475577_1_En_9_Chapter/475577_1_En_9_Fig3_HTML.png — Fig. 9.3

Push

On the 3D high definition manometric image the simulated defecation generates a symmetric increase in the caliber of the functional anal canal (arrow 3) compared to the seconds immediately preceding the pushing maneuver.

9.4 Recto-Anal Inhibitory Reflex

The evaluation of the recto-anal inhibitory reflex (RAIR) involves the distension of the rectum walls through the progressive insufflation of air inside the balloon placed on the anorectal manometry probe.

The pressure increase appreciated in the rectum (arrow 1), if reflex arc is preserved, will correspond to a relaxation of the sphincterial apparatus which, in the 3D manometric image, results in an increase in the caliber of the functional anal canal (arrow 2) compared to the seconds immediately preceding the air blowing. On the 2D manometric color-contour plot a color change towards the colder colors (arrow 3) of the pressure scale is shown RAIR may be elicited by 20 ml air blowing, but is good practice to evaluate it with progressive insufflations until reaching a value of at least 60 ml.

../images/475577_1_En_9_Chapter/475577_1_En_9_Fig4_HTML.png — Fig. 9.4

Recto-anal inhibitory reflex

9.5 Cough Reflex

The evaluation of the cough reflex allows to verify the integrity of the reflex arc. It is composed of the pudendal nerves and sacral roots, which permits fecal continence during such maneuvers: the act of cough causes an increase in intraabdominal pressure to which corresponds a rise in sphincter pressure caused by external sphincter muscle contraction. Loss of this reflex, due to neurological or mechanical causes, such as traumas or nerve compression, could lead to episodes of fecal incontinence.

In Fig. 9.5 it is possible to notice, during cough maneuver, a pressure rising in the rectal sensors (arrow 1) which activates the physiological reflex arc that causes contraction of the external sphincter muscle (warmer colors along sphincter sensors) (arrow 2).

../images/475577_1_En_9_Chapter/475577_1_En_9_Fig5_HTML.png — Fig. 9.5

Cough reflex

9.6 Paradoxical Puborectalis Contraction

The paradoxical puborectalis contraction is a dyssynergic condition of the pelvic floor muscles that may appear during straining: in physiological conditions the puborectalis muscle sling, during wilting, undergoes a relaxation, straightening the way of expulsion of the stools.

In this type of dyssynergic defecation there is a muscular incoordination characterized by a paradoxical contraction of the puborectalis muscle. In this patients a correct propulsive thrust through the bearing down maneuver is detectable (Fig. 9.6, arrow 1) but the paradoxical contraction of the pubo-rectal is sling prevents physiological evacuation, leading to an obstructed defecation.

This dyssynergic condition manifests itself on the high resolution manometric color-contour plot, while patient is asked to strain, with a pressure change towards warmer colors (rather than the physiological color change towards colder colors) with its peak on the proximal portion of the functional anal canal (arrow 2) (Fig. 9.6).

../images/475577_1_En_9_Chapter/475577_1_En_9_Fig6_HTML.png — Fig. 9.6

Paradoxical puborectalis contraction

High definition manometric image allows to appreciate the presence of an asymmetrical pressure increase located on the posterior portion of the anal canal (arrow 3), due to the typical sling course of the puborectalis muscle.

9.7 Paradoxical Contraction with External Anal Sphincter Recruitment

Paradoxical contraction during straining with external anal sphincter recruitment is shown in Fig. 9.7: the 2D manometric color plot shows a change towards warmer colors represented all along the anal sphincter (arrow 1) due to paradoxical contraction of the external anal sphincter, associated with rectal pressure increase (arrow 2) due to bearing down maneuver.

../images/475577_1_En_9_Chapter/475577_1_En_9_Fig7_HTML.png — Fig. 9.7

Paradoxical contraction with external anal sphincter recruitment

3D high definition manometric image shows a diffuse caliber reduction of the anal canal (arrow 3): it is noteworthy that in this patient it is not possible to appreciate the posterior pressure increase typical of paradoxical puborectalis contraction.

9.8 Anal Sphincter Impaired Relaxation

The anal sphincter impaired relaxation is also a dyssynergic phenomenon that manifests itself during simulated defecation: on the 2D manometric color-contour plot it is possible to appreciate a correct propulsive thrust during the bearing down maneuver (Fig. 9.8, arrow 1) associated, in this case, with an absence of the color change towards the colder colors of the pressure scale (as one would expect to find in case of physiological conditions); anal sphincter impaired relaxation is characterized, instead, by a permanence of the high pressure zone (arrow 2) compared to the pre-pushing phase.

../images/475577_1_En_9_Chapter/475577_1_En_9_Fig8_HTML.png — Fig. 9.8

Anal sphincter impaired relaxation

The physiological increase in the caliber of the anal canal is not appreciated in the 3D high definition manometric image; on the contrary, it is possible to detect the constant presence of the “dumb-bell shape” image appreciable in resting condition (arrow 3).

9.9 Insufficient Resting Pressure

An impaired resting pressure could lead to episodes of fecal incontinence: the major predisposing factor is certainly childbirth and possible peripartum episiotomy; other causes can be traumatic sphincter lesions, neurological causes, inflammatory bowel diseases, or iatrogenic causes secondary to surgery for anal fissures, perianal fistulas, or tumors.

In Fig. 9.9a it is possible to appreciate a reduced resting pressure: the HPZ is characterized by reduced length and colder colors of the manometric scale (arrow 1) if compared to physiological pattern. The 3D high definition image shows an increased caliber of the anal canal at rest (arrow 2) compared to physiological dumbbell appearence.