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Anatomy of the Rectum and Anus
Published in Han C. Kuijpers, Colorectal Physiology: Fecal Incontinence, 2019
A. P. Meagher, W. J. Adams, D. Z. Lubowski, D. W. King
The nerve supply is both intrinsic, via purinergic nerves in the wall of the anorectum, and extrinsic, via the autonomic nerves. The rectoanal inhibitory reflex is mediated via the intrinsic nerves.16 The role of the extrinsic nerves is less well understood. Stimulation of the presacral sympathetic nerves has been shown in some studies to cause IAS relaxation16 and contraction in other studies.17 Tonic excitatory discharge has been implicated from observations after spinal anesthesia.18 The physiological role of the sympathetic nerves, therefore, remains unknown, but they may influence both contraction and relaxation through different firing rates or by modifying ganglionic transmission.19 The effect of the parasympathetic nerves on IAS function is unknown, although it has been suggested that at rest there is no tonic parasympathetic discharge affecting sphincter tone.18
Physiology
Published in Peter Sagar, Andrew G. Hill, Charles H. Knowles, Stefan Post, Willem A. Bemelman, Patricia L. Roberts, Susan Galandiuk, John R.T. Monson, Michael R.B. Keighley, Norman S. Williams, Keighley & Williams’ Surgery of the Anus, Rectum and Colon, 2019
Anwen Williams, Martyn D. Evans
The rectum is sensitive to distension alone, whereas the anal canal is sensitive to temperature, touch and pain. The lining of the anal canal above the dentate line consists of an area of mucosa which is richly innervated and can distinguish between solid, liquid and gas. The internal sphincter relaxes transiently when the rectum distends, and this enables the sensitive mucosa to determine the nature of the bowel content. This rectoanal inhibitory reflex is essential for normal function, as the rectum can evacuate flatus without releasing any solid or liquid material. A loss of the rectoanal inhibitory reflex is pathognomic of Hirschsprung’s disease. Passing flatus relieves distension of the rectum and can facilitate deferring rectal evacuation of solid and liquid motion.
Surgery For Hirschsprung's Diseasee
Published in P Ronan O’Connell, Robert D Madoff, Stanley M Goldberg, Michael J Solomon, Norman S Williams, Operative Surgery of the Colon, Rectum and Anus Operative Surgery of the Colon, Rectum and Anus, 2015
The diagnosis of HD is based on the absence of ganglion cells and increased acetylcholinesterase staining of hypertrophied nerve fibers in rectal biopsies. Rectal biopsies are usually obtained with a special suction device. Common pitfalls include an inadequate superficial biopsy sample without submucosa, especially in older children, too distal biopsy site in the very distal rectum just proximal to the dentate line with physiological aganglionosis, and weak acetylcholinesterase staining occasionally associated with long segment disease. In unclear cases, repeated rectal suction or open biopsy and/or anorectal manometry with an absent rectoanal inhibitory reflex will ultimately reveal the diagnosis. Patients should also undergo routine preoperative assessment for associated chromosomal, cardiac, and genitourinary anomalies.
Anorectal Function and Quality of Life in IBD Patients With A Perianal Complaint
Published in Journal of Investigative Surgery, 2021
Francesco Litta, Franco Scaldaferri, Angelo Parello, Veronica De Simone, Antonio Gasbarrini, Carlo Ratto
ARM was performed using a computerized system (EB Neuro, Florence, Italy) equipped with a water-perfused 8-channel catheter; an additional channel was used to perfuse a balloon located at the tip of the catheter. The maximum resting pressure, maximum squeeze pressure, rectal sensory thresholds (first constant sensation, defecatory desire, and maximum tolerated volumes), and the rectoanal inhibitory reflex (RAIR) were investigated. The presence of a dyssynergic motor pattern at the ARM was diagnosed when the patient was not able to reduce the anal canal pressures and/or by assessing the inability to elevate rectal pressure during simulated defecation with a rectal balloon inflated with 50 ml of air [7].
Management of Neurogenic Bowel Dysfunction in Adults after Spinal Cord Injury
Published in The Journal of Spinal Cord Medicine, 2021
Jeffery Johns, Klaus Krogh, Gianna M. Rodriguez, Janice Eng, Emily Haller, Malorie Heinen, Rafferty Laredo, Walter Longo, Wilda Montero-Colon, Catherine S. Wilson, Mark Korsten
Normal defecation is preceded by a mass movement of stool from the colon to the rectum. Stretch of the rectal wall initiates the defecation reflex, which stimulates contraction of the rectal wall through a reflex arch between the rectum and the sacral spinal cord. Furthermore, the rectoanal inhibitory reflex (RAIR) causes relaxation of the internal anal sphincter muscle during rectal distension. It is mediated by intramural nerve fibers but enhanced by the parasympathetic nerve fibers from the sacral spinal cord (S2-S4). Defecation can be interrupted by voluntary contraction of the external anal sphincter muscle.
Determinants of optimal bowel function in ileal pouch-anal anastomosis – physiological differences contributing to pouch function
Published in Scandinavian Journal of Gastroenterology, 2018
Marie Louise Sunde, Petr Ricanek, Tom Øresland, Jørgen Jahnsen, Nazir Naimy, Arne Engebreth Færden
Sphincter function in the well and poorly function groups is illustrated in Table 3. None of the patients had a rectoanal inhibitory reflex. There were no significant differences in RAP (p = .571), maximum squeeze pressure (p = .739) or pouch pressure at urge (p = .620) in patients with or without leakage. RAP was not correlated to urge volume (p = .810).