Intestinal ultrasound, an underutilized tool for assessing colonic motility

EditorialIntestinal ultrasound, an underutilized tool for assessing colonic motilityGabrio Bassotti and Giovanni MaconiGabrio BassottiGastroenterology and Hepatology Section, Department of Medicine and Surgery, University of Perugia, Perugia, ItalyGastroenterology Unit, Perugia General Hospital, Perugia, Italy, andGiovanni MaconiGastroenterology Unit, Department of Biomedical and Clinical Sciences, "L.Sacco" Hospital, University of Milano, Milano, ItalyPublished Online:05 Dec 2023https://doi.org/10.1152/ajpgi.00237.2023This is the final version - click for previous versionMoreSectionsPDF (207 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Widely available inexpensive tools to assess the physiology of the gastrointestinal tract are a major unmet need for the management of functional gastrointestinal disorders. The techniques currently used in clinical practice are mainly devoted to investigating single and specific features of gastrointestinal physiology such as motility, secretion, and sensitivity. Other techniques, such as scintigraphy, breath tests, the radiopaque markers transit time test, and functional radiologic or magnetic resonance studies are rarely used in clinical practice because they are invasive, time consuming, expensive, or not available (1). In addition, these techniques provide only specific information on physiology, further requiring preliminary assessment of anatomy by means of other investigations such as endoscopy or radiographic imaging. Therefore, imaging techniques able to provide information both on anatomical structure and physiological insights of the gastrointestinal tract are sorely needed. In the past years, many efforts have been made in this direction to implement anatomic imaging of the gut coupled with a physiological assessment, particularly by means of noninvasive techniques such as magnetic resonance (MR) (2) and intestinal ultrasound (3), which provide detailed real-time assessment of the gut, especially about its motility and content.However, functional MR remains an expensive and scarcely available technique, mainly used for scientific purposes; furthermore, the relative brevity of recordings is a major limitation to assess physiologic phenomena, especially in the large bowel. In contrast, ultrasound is one the most widely used imaging tools for abdominal complaints, in particular as a first-line investigation, and it has gained a prominent role in the clinical arena (4). Several studies have shown that ultrasound is requested in more than 50% of patients with irritable bowel syndrome (IBS) (5), especially to distinguish it from Crohn's disease, also thanks to its high accuracy and cost effectiveness (6). After being applied to the study of gastric and small bowel pathophysiology, intestinal ultrasound is now increasingly being applied to the study of the large bowel. The potential of intestinal ultrasound relies not only on the real-time assessment of motility but also on detecting morphological and dynamic features of the gut, likely associated with its function, especially when the viscus is filled with liquids (7). For instance, in IBS and uncomplicated diverticular disease of the colon, intestinal ultrasound may show increased thickening of the muscularis propria of the sigmoid colon compared with healthy subjects, likely an expression of its persistent contraction (8). Intestinal ultrasound is also able to assess the features of intestinal content. In chronic constipation, it can detect hard stools within the colon, including the presence of fecal impaction within the rectum, and also allows the diagnosis of megarectum (9). Fecal loading and its consistency, variously organized in rather complex scores, not yet validated, have been proposed as potentially useful parameters of colonic function (10). These scores, based on the transverse diameters of the colonic segments, the acoustic shadowing of the contents, and haustral appearances, have shown a good correlation with CT findings of stool and/or gas distribution and with the colonic transit time evaluated by radiopaque markers (10).However, most of the scientific literature, especially that devoted to colonic function, primarily tackled pathological conditions, somewhat forgetting the physiological mechanisms of the colon. Indeed, based on the above considerations, intestinal ultrasound has great potential for physiological assessment of colonic motor function, even for relatively prolonged periods of time. Recently, a study by Hussein et al. (11) investigated the role of colonic ultrasonography on healthy subjects, assessing spontaneous haustral activities and analyzing specifically the rhythmic motor patterns. Ultrasonography recordings of the ascending, transverse, and descending colon identified three distinct rhythmic motor patterns: the 1 cycle/min and the 3 cycles/min cyclic motor pattern throughout the whole colon and the 12 cycles/min cyclic motor pattern in the ascending colon. To date, evaluation of the same colonic rhythmic activity was only possible by means of electromyographic (12) or manometric (13, 14) techniques necessitating deep colonic intubation and therefore quite invasive and not universally available, especially to study healthy individuals for physiological purposes.The potential of ultrasound to show rhythmic motor patterns of the human colon, associated with interstitial cells of Cajal-associated pacemaking activity, allows us to accurately identify and quantify colonic motility under physiological conditions. Furthermore, such information might be translated to the clinical arena and applied to the dysmotilities found in pathological conditions, which up to now still require invasive methods to be detected not only for diagnostic purposes but also for monitoring therapies (15–17). However, the study of colonic motility by ultrasound scans is still hampered by some limitations: 1) intestinal ultrasound is operator-dependent, and requires specialized training programs to learn this skill; 2) good data on "normal" patients are still lacking, as well as validated scoring systems for colonic motility; 3) the challenge to capture motor patterns [such as the high-amplitude propagating contractions, the manometric equivalent of colonic mass movements (18,19), which may only arise once every few hours and that likely will need a stimulus (e.g., meals, colonic distention, bisacodyl, etc.) to appear under ultrasound; 4) if a response to a meal is to be studied, this may be inconsistent, late, and variable; 5) the need for colon preparation and intake of sorbitol before ultrasound, factors somewhat limiting a true physiological assessment; and 6) the need to investigate a larger number of subjects for prolonged time periods. Nevertheless, the refinement of ultrasound techniques and their potential applicability to physiological investigations of the large bowel motor activity must be finally recognized. Hopefully, we will soon see more and more studies carried out under physiological conditions (e.g., unprepared colon) and in response to stimulations; this will provide us with further insights into the physiological phenomena of this interesting viscus.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the authors.AUTHOR CONTRIBUTIONSG.B. and G.M. conceived and drafted manuscript; edited and revised manuscript; approved final version of manuscript.REFERENCES1. Keller J, Bassotti G, Clarke J, Dinning P, Fox M, Grover M, Hellström PM, Ke M, Layer P, Malagelada C, Parkman HP, Scott SM, Tack J, Simren M, Törnblom H, Camilleri M, International Working Group for Disorders of Gastrointestinal Motility and Function. 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Bassotti G. 1907-2020: more than one century of colonic mass movements in humans. Am J Physiol Gastrointest Liver Physiol 320: G117–G124, 2021. doi:10.1152/ajpgi.00375.2020.Link | ISI | Google ScholarAUTHOR NOTESCorrespondence: G. Bassotti (gabassot@gmail.com). Download PDF Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 326Issue 1January 2024Pages G1-G2 Crossmark Copyright & PermissionsCopyright © 2024 the American Physiological Society.https://doi.org/10.1152/ajpgi.00237.2023PubMed37961815History Received 18 October 2023 Accepted 6 November 2023 Published online 5 December 2023 Published in print 1 January 2024 Keywordscoloncolon motilityultrasound Metrics