Additional criteria on scintigraphic testing for diagnosis of rapid colonic transit in patients with chronic diarrhea

Colonic transit (CT) measured by validated scintigraphy using ¹¹¹In-labeled activated charcoal particles is summarized using geometric center (GC) of isotopic distribution in four colonic regions and stool at 24 and 48 h. Diagnosis of rapid CT is currently based on GC24 ≥4.4 in females and >4.7 in males, which lack sensitivity. Our aim was to evaluate, in patients with chronic diarrhea with normal CT by GC24 and GC48, the diagnostic utility of CT change (∆GC) relative to sex-matched normal values.

We evaluated two adult patient cohorts: 701 clinical patients (1994-2023) with chronic diarrhea and 76 research participants with irritable bowel syndrome with diarrhea (N = 63) or bile acid diarrhea (BAD, N = 13). Results of ∆GC were compared to 220 healthy controls' 95th percentiles (%ile) (≥2.0 females and ≥2.2 males). In the research cohort, we also analyzed (Spearman correlation) colonic ∆GC with ascending colon emptying T_1/2 (AC T_1/2), average stool frequency and consistency based on a daily diary, total fecal bile acid (BA) concentration, and % primary BA in a single stool sample.

Among 701 clinical patients with normal GC24, 160 (22.3%) had rapid CT based on ∆GC 95th %ile in health. Among 76 research participants, an additional 20.6% IBS-D and 23% BAD had rapid CT ∆GC. Younger age and absence of diabetes mellitus were predictive of rapid ∆GC. ∆GC significantly correlated with AC T_1/2 and with fecal BA.

∆GC identified an additional 21%-23% patients with rapid colonic transit among patients with diarrhea and normal GC24.