S1827 External Anal Sphincter Plication: A Novel Surgical Approach to Enhance the Anal Canal Function

The length at which a muscle operates in vivo (operational length) and the length at which it generates maximal force (optimal length) may be quite different. We studied active and passive length-tension characteristics of external anal sphincter (EAS) in vivo and in vitro to determine the optimal and operational length of rabbit EAS. For the in vitro studies, rings of EAS ( n = 4) were prepared and studied in a muscle bath under isometric conditions. For in vivo studies, female rabbits ( n = 19) were anesthetized and anal canal pressure was recorded by use of a sleeve sensor placed in the custom-designed catheter holders of 4.5-, 6-, and 9-mm diameters. Measurements were obtained at rest and during EAS electrical stimulation. Sarcomere length of EAS muscle was measured by laser diffraction technique with no probe and three probes in the anal canal. In vitro studies revealed 2,054 mN/cm2 active tension at optimal length. In vivo studies revealed a probe size-dependent increase in anal canal pressure and tension. Maximal increase in anal canal tension with stimulation was recorded with the 9-mm probe. Increases in anal canal tension with increase in probe size were completely abolished by pancuronium bromide. EAS muscle sarcomere length without and with 9-mm probe in the anal canal were 2.11 ± 0.08 and 2.99 ± 0.07 μm, respectively. Optimal sarcomere length, based on the thin filament length measured by thin filament analysis, is 2.44 ± 0.10 μm. These data show that the operational length of EAS is significantly shorter than its optimal length. Our findings provide insight into EAS function and we propose the possibility of increasing anal canal pressure by surgical manipulation of the EAS sarcomere length.

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Novel applications of external anal sphincter muscle sarcomere length to enhance the anal canal function

Neurogastroenterology & Motility ◽

10.1111/j.1365-2982.2010.01608.x ◽

2010 ◽

Vol 23 (1) ◽

pp. 70-e7 ◽

Cited By ~ 14

Author(s):

M. R. Rajasekaran ◽

Y. Jiang ◽

V. Bhargava ◽

R. L. Lieber ◽

R. K. Mittal

Keyword(s):

Anal Canal ◽

Anal Sphincter ◽

External Anal Sphincter ◽

Sarcomere Length ◽

Sphincter Muscle ◽

Anal Sphincter Muscle ◽

Novel Applications ◽

External Anal Sphincter Muscle

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Quantification of axial forces in rectum-anal canal of the cat

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1986.250.2.g260 ◽

1986 ◽

Vol 250 (2) ◽

pp. G260-G265

Author(s):

J. Krier ◽

T. Adams

Keyword(s):

Smooth Muscle ◽

Anal Canal ◽

Anal Sphincter ◽

Internal Anal Sphincter ◽

External Anal Sphincter ◽

Striated Muscle ◽

Muscle Tone ◽

Neural Pathways ◽

Axial Forces

A newly developed probe was used to measure in vivo axial forces in the rectum-anal canal of the anesthetized cat. Spontaneous contractions of the smooth muscle of the internal anal sphincter were recorded, as were neurally evoked contractions of striated muscle of the external anal sphincter. Bilateral electrical stimulation (1-10 V, 1-5 Hz, 0.05 ms duration) of motor axons in pudendal nerves elicited two responses. One was synchronous phasic contractions of skeletal muscle fibers of the external anal sphincter that were not abolished by atropine but were by gallamine trithiodide. They occurred at short latencies (1-2 ms) and were mediated through low-threshold (1-3 V, 0.05 ms duration) efferent axons in the pudendal nerves. Contraction times ranged from 45 to 60 ms, and contraction duration ranged from 100 to 160 ms. The second response was a progressive elevation in tone of the anal canal due to contractions either of the smooth muscle of the rectum and/or that of the internal anal sphincter. The elevation in smooth muscle tone concomitant with pudendal nerve stimulation may be due to reflex activation of cholinergic neural pathways, since the response was abolished by atropine.

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Purse-string morphology of external anal sphincter revealed by novel imaging techniques

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00338.2013 ◽

2014 ◽

Vol 306 (6) ◽

pp. G505-G514 ◽

Cited By ~ 22

Author(s):

Ravinder K. Mittal ◽

Valmik Bhargava ◽

Geoff Sheean ◽

Melissa Ledgerwood ◽

Shantanu Sinha

Keyword(s):

Anal Canal ◽

Anal Sphincter ◽

Muscle Fiber ◽

Anal Incontinence ◽

External Anal Sphincter ◽

Diffusion Tensor ◽

Imaging Techniques ◽

Three Dimensional ◽

Purse String ◽

Lidocaine Injection

The external anal sphincter (EAS) may be injured in 25–35% of women during the first and subsequent vaginal childbirths and is likely the most common cause of anal incontinence. Since its first description almost 300 years ago, the EAS was believed to be a circular or a “donut-shaped” structure. Using three-dimensional transperineal ultrasound imaging, MRI, diffusion tensor imaging, and muscle fiber tracking, we delineated various components of the EAS and their muscle fiber directions. These novel imaging techniques suggest “purse-string” morphology, with “EAS muscles” crossing contralaterally in the perineal body to the contralateral transverse perineal (TP) and bulbospongiosus (BS) muscles, thus attaching the EAS to the pubic rami. Spin-tag MRI demonstrated purse-string action of the EAS muscle. Electromyography of TP/BS and EAS muscles revealed their simultaneous contraction and relaxation. Lidocaine injection into the TP/BS muscle significantly reduced anal canal pressure. These studies support purse-string morphology of the EAS to constrict/close the anal canal opening. Our findings have implications for the effect of episiotomy on anal closure function and the currently used surgical technique (overlapping sphincteroplasty) for EAS reconstructive surgery to treat anal incontinence.

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Genesis of anal canal pressures in the opossum

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1986.251.6.g765 ◽

1986 ◽

Vol 251 (6) ◽

pp. G765-G771 ◽

Cited By ~ 26

Author(s):

P. J. Culver ◽

S. Rattan

Keyword(s):

Anal Canal ◽

Anal Sphincter ◽

Internal Anal Sphincter ◽

External Anal Sphincter ◽

Sphincter Pressure ◽

Electromyographic Activity ◽

Sphincter Muscle ◽

Anal Sphincter Muscle ◽

Adrenergic Antagonist ◽

Alpha Chloralose

The purpose of the present investigation was to examine the role of the internal and external anal sphincters in the maintenance of resting pressures in the anal canal. The studies were performed in opossums anesthetized with alpha-chloralose. The radial and axial pressures in the anal canal were monitored using a continuously perfused catheter assembly. Electromyography of the external anal sphincter was monitored using bipolar tungsten hook electrodes. To examine the contribution of the external anal sphincter and surrounding skeletal muscle to the resting tone in the anal canal, pancuronium bromide was administered in a dose that abolished the electromyographic activity of the external anal sphincter muscle. The abolition of external anal sphincter activity did not modify the peak anal canal pressures, suggesting that these pressures are due to the internal anal sphincter. The alpha-adrenergic antagonist, phentolamine, did not modify the anal canal pressure, suggesting that basal internal anal sphincter pressure is not due to tonic adrenergic activity. Tetrodotoxin in a dose that produced obliteration of the anorectal reflex causing anal sphincter relaxation did not produce any change in the peak anal canal pressures. These studies show that the resting pressures in the anal canal of opossums are due to myogenic properties of the internal anal sphincter.

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Age-related external anal sphincter muscle dysfunction and fibrosis: possible role of Wnt/β-catenin signaling pathways

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00209.2017 ◽

2017 ◽

Vol 313 (6) ◽

pp. G581-G588 ◽

Cited By ~ 13

Author(s):

M. Raj Rajasekaran ◽

Sadhana Kanoo ◽

Johnny Fu ◽

My-Uyen (Lilly) Nguyen ◽

Valmik Bhargava ◽

...

Keyword(s):

Connective Tissue ◽

Anal Canal ◽

Anal Sphincter ◽

External Anal Sphincter ◽

Muscle Thickness ◽

Sphincter Muscle ◽

Anal Sphincter Muscle ◽

Age Related ◽

And Function

Studies show an age-related increase in the prevalence of anal incontinence and sphincter muscle atrophy. The Wnt/β-catenin signaling pathway has been recently recognized as the major molecular pathway involved in age-related skeletal muscle atrophy and fibrosis. The goals of our study were to 1) evaluate the impact of normal aging on external anal sphincter (EAS) muscle length-tension (L-T) function and morphology and 2) specifically examine the role of Wnt signaling pathways in anal sphincter muscle fibrosis. New Zealand White female rabbits [6 young (6 mo of age) and 6 old (36 mo of age)] were anesthetized, and anal canal pressure was measured to determine the L-T function of EAS. Animals were killed at the end of the study, and the anal canal was harvested and processed for histochemical studies (Masson trichrome stain for muscle/connective tissue) as well as for molecular markers for fibrosis and atrophy [collagen I, β-catenin, transforming growth factor-β (TGF-β), atrogin-1, and muscle-specific RING finger protein-1 (MuRF-1)]. The L-T was significantly impaired in older animals compared with young animals. Anal canal sections stained with trichrome showed a significant decrease in the muscle content (52% in old compared with 70% in young) and an increase in the connective tissue/collagen content in the old animals. An increased protein and mRNA expression of all the fibrosis markers was seen in the older animals. Aging EAS muscle exhibits impairment of function and increase in connective tissue. Upregulation of atrophy and profibrogenic proteins with aging may be the reason for the age-related decrease in anal sphincter muscle thickness and function. NEW & NOTEWORTHY Our studies using a female rabbit model show age-related alterations in the structure and function of the external anal sphincter (EAS) muscle. We used endoluminal ultrasound to measure age-related changes in EAS muscle thickness. We employed Western blot and quantitative PCR to demonstrate age-related changes in the levels of important fibrogenic as well as atrophy markers. Our findings may have significant clinical implications, i.e., use of specific antagonists to prevent age-related EAS muscle dysfunction.

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Contribution of the external anal sphincter to the pressure zone in the anal canal

Gut ◽

10.1136/gut.6.1.64 ◽

1965 ◽

Vol 6 (1) ◽

pp. 64-68 ◽

Cited By ~ 198

Author(s):

H. L. Duthie ◽

J. M. Watts

Keyword(s):

Anal Canal ◽

Anal Sphincter ◽

External Anal Sphincter ◽

Pressure Zone

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Ultrasound Assessment of the Internal Anal Sphincter in Women with Fecal Incontinence and Posterior Vaginal Wall Prolapse (Rectocele)

Donald School Journal of Ultrasound in Obstetrics & Gynecology ◽

10.5005/jp-journals-10009-1211 ◽

2011 ◽

Vol 5 (4) ◽

pp. 339-342

Author(s):

Hossam H Kamel ◽

Ahmad G Serour ◽

Laila AS Mousa

Keyword(s):

Fecal Incontinence ◽

Anal Canal ◽

Anal Sphincter ◽

Internal Anal Sphincter ◽

External Anal Sphincter ◽

Vaginal Wall ◽

Sympathetic Tone ◽

Abdominal Pressure ◽

Muscular Tissue ◽

Posterior Vaginal Wall

ABSTRACT Rupture of the internal anal sphincter (IAS) causes its weakness and it will not withstand increases of abdominal pressure, and fecal incontinence (FI) will occur. Recently, we put forward a novel concept on the physiology of defecation. Defecation is divided into two stages: First stage before training and second stage starts at the age of about 2 years, when the mother starts to teach her child how to hold up himself. This is gained by maintaining high alpha-sympathetic tone at the IAS, thus keeping it closed all the time till there is a need to pass stool or flatus, and the time and place are convenient. On defecation, six neuromuscular actions take place under the control of the CNS: (1) The person will relax the external anal sphincter, (2) he will lower the gained high alpha-sympathetic tone at the IAS, thus opening the anal canal, (3) he will relax the pelvic floor muscles bringing the rectum and the anal canal into one axis, (4) the abdominal and diaphragmatic muscles contract to increase the abdominal pressure, (5) the muscles of the distal colon and rectum contract pushing the stool, (6) sequential contractions of the three parts of the external anal sphincter (EAS) that squeeze any residual contents in the anal canal. Thus, the anal canal is closed and empty under normal circumstances. The IAS is a collageno-muscular tissue cylinder that surrounds the anal canal. The IAS is intimately related to the posterior vaginal wall, and the vagina is over stretched in labor, childbirth trauma affects both the posterior vaginal wall and the IAS. Rupture of the collagen sheet of the IAS which causes its weakness is better demonstrated by imaging by 3D US. Normal vagina is a cylinder of collageno-elastic-muscular tissues. Its strong collagen sheet is responsible for keeping it in its normal upward position. Labors cause redundancy and weakness of the vaginal walls with subsequent prolapse; and lacerations of the IAS which is closely related to the posterior vaginal wall leading to FI.

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