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Review
. 2022 Sep 16:12:975386.
doi: 10.3389/fonc.2022.975386. eCollection 2022.

The role of colonic motility in low anterior resection syndrome

Chris Varghese  1 , Cameron I Wells  1   2 , Ian P Bissett  1   3 , Gregory O'Grady  1 , Celia Keane  1   4
Affiliations
Review

The role of colonic motility in low anterior resection syndrome

Chris Varghese et al. Front Oncol. .

Abstract

Low anterior resection syndrome (LARS) describes the symptoms and experiences of bowel dysfunction experienced by patients after rectal cancer surgery. LARS is a complex and multifactorial syndrome exacerbated by factors such as low anastomotic height, defunctioning of the colon and neorectum, and radiotherapy. There has recently been growing awareness and understanding regarding the role of colonic motility as a contributing mechanism for LARS. It is well established that rectosigmoid motility serves an important role in coordinating rectal filling and maintaining continence. Resection of the rectosigmoid may therefore contribute to LARS through altered distal colonic and neorectal motility. This review evaluates the role of colonic motility within the broader pathophysiology of LARS and outlines future directions of research needed to enable targeted therapy for specific LARS phenotypes.

Keywords: colonic motility; low anterior resection; low anterior resection syndrome (LARS); rectal cancer; rectosigmoid brake.

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Conflict of interest statement

GO’G, IB, and CK are members of The University of Auckland Spin-out companies: The Insides Company Ltd (GO’G, IB, CK), and Alimetry Ltd (GO’G). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Physiological mechanisms of defecation with a focus on the role of colonic motility. The cyclic motor pattern (CMP) which characterises the rectosigmoid brake regulates rectal filling in the continence/basal phase. During the pre-expulsive phase of defecation, high amplitude propagating contractions (HAPCs) and the cyclic motor pattern facilitate antegrade transit. Important mechanisms of continence include ability of voluntary contraction of the external anal sphincter (EAS) and the rectosigmoid brake. The expulsive phase of defecation is facilitated by propulsive rectal contractions, voluntary EAS relaxation, and reflex relaxation of the internal anal sphincter (IAS) and pelvic floor (PF) muscles. Refer to refs (16, 44) for extended details.
Figure 2
Figure 2
Putative mechanisms contributing to low anterior resection syndrome during the basal, pre-expulsive, and expulsive phases. Mediators of injury arising from surgery, radiotherapy, and ileostomies (as described in Figure 5 ) are described in this figure. Diverting ileostomies may cause diversion colitis, bile salt malabsorption, small intestinal bacterial overgrowth (SIBO), and/or colonic dysbiosis. Similarly, changes in colo/rectoanal sensation, neorectal compliance, sphincter, and pelvic floor dyssynergia, altered distal colonic motility, and limited external anal sphincter (EAS) function also contribute. Little is known about the pathophysiological mechanisms for low anterior resection syndrome during the expulsive phase of defecation and more research is required in this area.
Figure 3
Figure 3
Adapted from Keane et al. with permission. Differences in the cyclic motor pattern in low anterior resection syndrome (LARS) compared to post-low anterior resection patients without LARS, and healthy controls. (A) number of antegrade contractions, (B) number of retrograde contractions, (C) amplitude of antegrade propagating contractions, (D) amplitude of retrograde propagating contractions, (E) distance of propagation of antegrade contractions, and (F) distance of propagation of retrograde propagating contractions. The resection group is made up of patients who scored ≤20 on the LARS score.
Figure 4
Figure 4
Adapted from Vather et al., 2016 with permission. Density analysis mapping of the number of propagating events occurring within 5 cm of the anastomosis. Some 47% of all propagating contractions occurred within 2 cm of the anastomosis (shaded area), with no drop-off at the site of the anastomosis.
Figure 5
Figure 5
Flow diagram of mechanisms of injury as a consequence of surgery, radiotherapy and stoma formation. SCFA, short chain fatty acids; ENS, enteric nervous system; rectoanal inhibitory reflex, RAIR.
See this image and copyright information in PMC

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