Abstract
BackgroundPigmented bile salts darken the small-bowel lumen and are present with bile acid, which is involved in the development of bowel habits. The small-bowel water content (SBWC) in the ileum could represent the colonic environment, but no studies have focused on this feature. However, measurement of crude SBWC can be challenging because of the technical difficulty of the endoscopic approach without preparation. Our aim was to evaluate optically active bile pigments in the SBWC of patients with abnormal bowel habits using capsule endoscopy (CE) to investigate the impact of bile acid on bowel habits.MethodsThe study population included 37 constipated patients, 20 patients with diarrhea, and 77 patients with normal bowel habits who underwent CE between January 2015 and May 2018. Patients with secondary abnormal bowel habits were excluded. In addition to conventional imaging, we used flexible spectral imaging color enhancement (FICE) setting 1 imaging, in which the effects of bile pigments on color are suppressed. Intergroup color differences of SBWC in the ileum (ΔE) were evaluated from conventional and FICE setting 1 images. Color values were assessed using the CIE L*a*b* color space. Differences in SBWC lightness (black to white, range 0–100) were also evaluated.ResultsThe ΔE values from the comparison of conventional images between patients with constipation and with normal bowel habits and between patients with diarrhea and with normal bowel habits were 12.4 and 11.2, respectively. These values decreased to 4.4 and 3.3, respectively, when FICE setting 1 images were evaluated. Patients with constipation and diarrhea had significantly brighter (34.4 versus 27.6, P < .0001) and darker (19.6 versus 27.6, P < .0001) SBWC lightness, respectively, than patients with normal bowel habits. The FICE setting 1 images did not reveal significant differences in SBWC lightness between those with constipation and with normal bowel habits (44.1 versus 43.5, P = .83) or between those with diarrhea and with normal bowel habits (39.1 versus 43.5, P = .20).ConclusionsDifferences in SBWC color and darkness in the ileum appear to be attributable to bile pigments. Therefore, bile pigments in SBWC may reflect bowel habits.
Highlights
Pigmented bile salts darken the small-bowel lumen and are present with bile acid, which is involved in the development of bowel habits
A deficiency of bile acid (BA) can contribute to the pathophysiology of constipation [4], while increasing intracolonic concentrations of BA can accelerate spontaneous peristalsis [5], with excessive BA resulting in loose stool consistency [6]
We were unable to find any previous studies that have investigated the contribution of BA in determining small-bowel water content (SBWC)
Summary
Pigmented bile salts darken the small-bowel lumen and are present with bile acid, which is involved in the development of bowel habits. In the gastrointestinal (GI) tract, BA plays a role in the modulation of fluid and electrolyte absorption and the regulation of GI motility [7,8,9]. Through these functions, BA is important for the development of bowel habits. We were unable to find any previous studies that have investigated the contribution of BA in determining small-bowel water content (SBWC). To evaluate the role of BA in the development of abnormal bowel habits, we investigated SBWC just proximal to the colon
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