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Trunk Muscles
Published in Eve K. Boyle, Vondel S. E. Mahon, Rui Diogo, Handbook of Muscle Variations and Anomalies in Humans, 2022
Eve K. Boyle, Vondel S. E. Mahon, Rui Diogo, Rowan Sherwood
The external anal sphincter is a circular muscle that surrounds the anus (Liu and Salem 2016; Standring 2016). It extends between the perineal body and the anococcygeal raphe (Liu and Salem 2016; Standring 2016). The deep part of the external anal sphincter blends with puborectalis (Liu and Salem 2016; Standring 2016). Fibers from the transverse perineal muscles and bulbospongiosus pass to the external anal sphincter (Peikert et al. 2015; Standring 2005, 2016). The anterior portion of the muscle is shorter in females (Sultan et al. 1994).
Basic anatomic principles of pediatric colorectal and reconstructive surgery
Published in Alejandra Vilanova-Sánchez, Marc A. Levitt, Pediatric Colorectal and Pelvic Reconstructive Surgery, 2020
The external anal sphincter is under voluntary (CNS) control. It is a continuation of the funnel of pelvic muscles [3]. Innervation is via the inferior rectal (anal) branch of the internal pudendal nerve (sympathetic) and perineal branch of S4. The parasagittal fibers and muscle complex are part of the levator ani muscle group (striated muscle).
The gastrointestinal tract
Published in Simon R. Knowles, Laurie Keefer, Antonina A. Mikocka-Walus, Psychogastroenterology for Adults, 2019
Christopher F.D. Li Wai Suen, Peter De Cruz
For conscious defaecation to happen, the brain sends signals for the puborectalis muscle to relax so that the angle between the rectum and the anus becomes less acute, and stool can travel from the rectum to the anus. The external anal sphincter also relaxes so that the anus opens, in preparation for passage of stool. At the same time, during straining, muscles of the abdominal wall contract, generating a rise in abdominal pressure and pushing stool down and out.
Analysis of the efficacy of biofeedback for faecal incontinence after surgery for anorectal malformation
Published in Annals of Medicine, 2022
Zhenqiang Zhang, Yuan Cheng, Junjun Ju, Weichen Shen, Zhubin Pan, Yuliang Zhou
Further analysis of the factors affecting therapeutic outcomes in paediatric patients with ARM following surgery found that in a univariate logistic regression, symptom duration and anal sphincter integrity were the principal factors influencing the therapeutic outcome, with the integrity of the anal sphincter being a positive influencing factor. Current studies have shown that in the paediatric population, there are no clearly defined values for the thickness of the external sphincter, and it is controversial whether its morphology and function change with age; however, the degree of anal sphincter injury following anal atresia appears to negatively influence defaecation [16,17]. It is speculated that the shorter the symptom duration, the less atrophy and the higher the integrity of the external anal sphincter and that external sphincter function might be effectively restored with biofeedback. This may be related to the fact that the ability to defaecate autonomously requires adequate innervation of the pelvic floor, rectum, and internal and external anal sphincters [18]. The anatomy and function of these muscles might be disrupted after surgical correction of ARM in paediatric patients, which highlights the importance of carefully preserving the anatomy below the peritoneal reflex site during anorectal surgery and minimising changes in rectal position during reconstruction to ensure minimal loss of function. The above speculation could well explain the results of the multivariate logistic regression analysis, which suggest that anal sphincter integrity is an independent risk factor for biofeedback.
Digital rectal stimulation as an intervention in persons with spinal cord injury and upper motor neuron neurogenic bowel. An evidenced-based systematic review of the literature
Published in The Journal of Spinal Cord Medicine, 2021
Mary Elizabeth S. Nelson, Merle Orr
Two studies focused solely on DRS as an intervention, one directly, and one through the application of pressure to the rectum with extrapolation of findings to DRS. The first study, Korsten et al.8 included 6 males with SCI and UMN-NB, age 44–55. Manometric evaluation of peristaltic contraction via insertion of a probe into the left colon was performed. Subjects served as their own controls and were evaluated before and after DRS was applied. The mean number of peristaltic waves per minute significantly increased during and after DRS (P = 0.05). Full evacuation of the bowels was noted after three to five cycles of DRS, with the longest duration of time to complete evacuation being 13 min. Shafik et al.'s9 study was a controlled randomized study of the effect of dilatation of the anal canal by a balloon-tipped catheter on rectal pressure. Eighteen healthy volunteers (10 men and 8 women,) and nine patients with SCI and UMN-NB (6 men and 3 women,) were evaluated. Repeated measures were taken before and after pudendal nerve block to paralyze the external anal sphincter to isolate the effects of internal anal sphincter dilation from external. The researcher found that distention of the anal canal resulted in a significant (P < 0.001) pressure rise. This data was extrapolated to simulate DRS on rectal pressures and the evacuation of bowels.
Botulinum toxin type-A infiltration of the external anal sphincter to treat outlet constipation in motor incomplete spinal cord injury: pilot cohort study
Published in Scandinavian Journal of Gastroenterology, 2021
Margarita Vallès, Sergiu Albu, Hatice Kumru, Fermín Mearin
Some studies indicate that BTX-A infiltration of the external anal sphincter (EAS) or the puborectalis muscle may improve outlet-type constipation [8,9]. Biofeedback is the standard treatment of the puborectalis syndrome [10], however when it fails the BTX-A infiltration of the EAS or puborectalis muscle can improve symptoms of constipation [9]. Furthermore, BTX-A infiltration have been shown to improve rectal emptying in patients with Parkinson's disease affected by outlet-obstruction constipation [11,12]. Nevertheless, the use of BTX-A infiltration in the treatment of neurogenic bowel symptoms in subjects with SCI has not been investigated. As we have published previously, one of the main pathophysiological mechanisms of bowel dysfunction in patients with motor-complete SCI below the T7 level, and motor-incomplete SCI, is outlet defecation with paradoxical contraction of the pelvic floor or lack of relaxation during the defecatory manoeuvre [13,14].