Comparative evaluation of the effect of sustained inflation and rapid inflation/deflation of the intrarectal balloon upon rectoanal inhibitory reflex parameters in asymptomatic subjects

Anorectal Manometry in Children: The Update on the Indications and the Protocol of the Procedure

Anorectal disorders are common in children. They are related to structural and/or functional abnormalities of the anorectum or pelvic floor with a variety of symptoms. Therefore, diagnostic tests to evaluate anorectal function can help to better understand the underlying pathophysiology and aetiology as well as facilitate patient management. During the past decades, substantial efforts have been made to improve anorectal function testing; however, more advanced investigations might lead to difficulties in interpretation. Additionally, a great diversity of equipment and protocols are used among centres, which may lead to heterogeneous interpretation of results. More studies to standardize methods of testing and validate reference values are strongly recommended in children. This review updates on the current indications and the protocol of anorectal manometry.

Prolonged-Release Oxycodone/Naloxone Improves Anal Sphincter Relaxation Compared to Oxycodone Plus Macrogol 3350

BACKGROUND

Opioid analgesics inhibit anal sphincter function and contribute to opioid-induced bowel dysfunction (OIBD). However, it is unknown whether the inhibition can be reduced by opioid antagonism with prolonged-release (PR) naloxone and how this compares to laxative treatment.

AIMS

To compare the effects of combined PR oxycodone/naloxone or PR oxycodone plus macrogol 3350 on anal sphincter function and gastrointestinal symptoms.

METHODS

A randomized, double-blind, crossover trial was conducted in 20 healthy men. Participants were treated for 5 days with combined PR oxycodone/naloxone or PR oxycodone plus macrogol 3350. Resting anal pressure, anal canal distensibility, and relaxation of the internal sphincter to rectal distension were evaluated before treatment (baseline) and on day 5. The Patient Assessment of Constipation Symptom (PAC-SYM) questionnaire, stool frequency, and stool consistency were assessed daily.

RESULTS

Both PR oxycodone/naloxone and PR oxycodone plus macrogol treatment decreased sphincter relaxation compared to baseline (- 27.5%; P < 0.001 and - 14.7%; P = 0.01). However, sphincter relaxation was increased after PR naloxone/oxycodone treatment compared to macrogol (difference = + 17.6%; P < 0.001). Resting anal pressure and anal canal distensibility did not differ between treatments. PAC-SYM abdominal symptoms score was lower during PR naloxone compared to macrogol (0.2 vs. 3.2; P = 0.002). The number of bowel movements was lower during PR naloxone versus macrogol (4.2 vs. 5.4; P = 0.035).

CONCLUSION

Relaxation of the internal anal sphincter was significantly better after PR oxycodone/naloxone treatment compared to PR oxycodone plus macrogol 3350. These findings highlight that OIBD may require specific therapy against the complex, pan-intestinal effects of opioids.

Topographic and manometric characterization of the recto-anal inhibitory reflex

BACKGROUND

Recto-anal inhibitory reflex (RAIR) is an integral part of normal defecation. The physiologic characteristics of RAIR along anal length and anterior-posterior axis are unknown. The aim of this study was to perform topographic and vector-graphic evaluation of RAIR along anal canal using high definition manometry (HDM), and examine the role of various muscle components.

METHODS

Anorectal topography was assessed in 10 healthy volunteers using HDM probe with 256 sensors. Recto-anal inhibitory reflex data were analyzed every mm along the length of anal canal for topographic, baseline, residual, and plateau pressures during five mean volumes of balloon inflation (15 cc, 40 cc, 71 cc, 101 cc, 177 cc), and in 3D by dividing anal canal into 4 × 2.1 mm grids.

KEY RESULTS

Relaxation pressure progressively increases along anal canal with increasing balloon volume up to 71 cc and thereafter plateaus. In 3D, RAIR is maximally seen at the middle and upper portions of anal canal (levels 1.2-3.2 cm) and posteriorly. Peak residual pressure was seen at proximal anal canal.

CONCLUSIONS & INFERENCES

Recto-anal inhibitory reflex is characterized by differential anal relaxation along anterior-posterior axis, longitudinally along the length of anal canal, and it depends on the rectal distention volume. It is maximally seen at internal anal sphincter pressure zone. Multidimensional analyses indicate that external anal sphincter provides bulk of anal residual pressure. Our findings emphasize importance of sensor location and orientation; as anterior and more distal location may miss RAIR.

Investigation of anal motor characteristics of the sensorimotor response (SMR) using 3-D anorectal pressure topography

Desire to defecate is associated with a unique anal contractile response, the sensorimotor response (SMR). However, the precise muscle(s) involved is not known. We aimed to examine the role of external and internal anal sphincter and the puborectalis muscle in the genesis of SMR. Anorectal 3-D pressure topography was performed in 10 healthy subjects during graded rectal balloon distention using a novel high-definition manometry system consisting of a probe with 256 pressure sensors arranged circumferentially. The anal pressure changes before, during, and after the onset of SMR were measured at every millimeter along the length of anal canal and in 3-D by dividing the anal canal into 4 × 2.1-mm grids. Pressures were assessed in the longitudinal and anterior-posterior axis. Anal ultrasound was performed to assess puborectalis morphology. 3-D topography demonstrated that rectal distention produced an SMR coinciding with desire to defecate and predominantly induced by contraction of puborectalis. Anal ultrasound showed that the puborectalis was located at mean distance of 3.5 cm from anal verge, which corresponded with peak pressure difference between the anterior and posterior vectors observed at 3.4 cm with 3-D topography (r = 0.77). The highest absolute and percentage increases in pressure during SMR were seen in the superior-posterior portion of anal canal, reaffirming the role of puborectalis. The SMR anal pressure profile showed a peak pressure at 1.6 cm from anal verge in the anterior and posterior vectors and distinct increase in pressure only posteriorly at 3.2 cm corresponding to puborectalis. We concluded that SMR is primarily induced by the activation and contraction of the puborectalis muscle in response to a sensation of a desire to defecate.