Bowel Transit Time May Be Accelerated in Colonic Diverticulosis Independent of Mucosal Serotonin Signaling

<b>Background/Objectives</b>: Colonic diverticulosis is a common condition in the elderly population and may affect bowel habits and reduce quality of life. Intestinal peristalsis is regulated by bioamines, which can influence bowel transit time. <b>Methods</b>: This prospective, comparative study included 23 patients. All participants were examined with colonoscopy with colonic mucosal biopsy and a bowel transit time test using SITZMARKS^® markers. The following bioamines were assessed in the colonic mucosa: 3-methoxy-4-hydroxyphenylglycol (MHPG), norepinephrine (NA), dopamine (DA), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT, serotonin), and 5-hydroxyindoleacetic acid (5-HIAA). <b>Results</b>: Among study participants, 14 had colonic diverticulosis and 9 were controls. There were no differences in age, sex, body mass, or weight between the groups. All patients with diverticulosis had left-sided diverticula and a DICA score of 1. None of the patients met the diagnostic criteria outlined in the ROME IV classification of functional gastrointestinal disorders. After 48 h, patients with diverticulosis tended to retain less SITZMARKS^® markers (mean of 1.14 vs. 6.78, <i>p</i> < 0.027), compared to the control group. Fewer patients with diverticulosis tended to have SITZMARKS^® markers visible in the X-ray image at 48 h (2 out of 14 versus 4 out of 9 patients, <i>p</i> < 0.262), compared to the control group. There were no differences in colonic mucosal concentrations of bioamines (5-HT, 5-HIAA, MHPG, NA, DA, HVA) between cases and controls. <b>Conclusions</b>: Bowel transit time in patients with colonic diverticulosis may be accelerated compared with controls, and this appears unrelated to bioamine metabolism.