Assessment of Small-bowel and Colonic Transit on Routine Gastric Emptying Scintigraphy: Establishment of Reference Values

Abstract

Purpose of the study: The primary objective was to establish the reference values for small-bowel and colonic transit within the context of the routine standard solid meal gastric emptying scintigraphy (GES). The secondary objective was to compare the small-bowel and colonic transit between the anterior view and geometric mean methods.

Materials and methods: Twenty-nine healthy controls underwent routine GES, with additional imaging at 24 h if feasible. Small-bowel transit was assessed using the index of small-bowel transit (ISBT), calculated as the ratio of terminal ileal reservoir counts to total abdominal counts at 4 h. Colonic transit was evaluated using the colonic geometric center (CGC) by dividing the large bowel into four segments, with an additional fifth segment accounting for the eliminated counts. Reference values were established based on the fifth percentile or mean ± 1.96 standard deviations. Rapid small-bowel transit was visually determined. Paired Samples t-test or Wilcoxon signed-rank test, as applicable, was used to compare the small-bowel and colonic transit between the anterior view and geometric mean methods. For comparing small-bowel and colonic transit between females and males, the Independent samples t-test or Mann-Whitney U-test was applied, as appropriate. The correlation between age and small-bowel and colonic transit was assessed using Spearman's rank correlation analysis.

Results: The reference value for small-bowel transit using the geometric mean method was established as ISBT >37% at 4 h, whereas rapid small-bowel transit was defined as the first visualization of activity in the cecum-ascending colon within 2 h. For colonic transit, the reference range was established as CGC 2.8-4.4 at 24 h. Comparing the anterior view and geometric mean methods, there were no significant differences in ISBT and CGC values (P ≥ 0.125). Gender did not affect small-bowel and colonic transit in both methods (P ≥ 0.378), and age showed no significant correlations (P ≥ 0.053).

Conclusion: This study determined the reference values for small-bowel and colonic transit in the Indian population using routine GES, avoiding the need for additional complex procedures. The results may be generalized to the Indian population, emphasizing the importance of assessing small-bowel and colonic transit in patients with normal gastric emptying parameters to enhance gastrointestinal transit evaluation.

Keywords: Colonic geometric center; colonic transit; gastric emptying scintigraphy; index of small-bowel transit; normal range; reference values; small-bowel transit; whole-gut transit.

Figure 1

Assessment of small-bowel transit using geometric mean method in a 50-year-old healthy male subject. (a) A large rectangular regions of interest (ROI) was drawn in each view on each time point of imaging (0, 1, 2, 4, and 24 h) encompassing the whole radioactivity in the abdomen region. The decay-corrected total abdominal counts (kcounts/min) at 4 h was 116.30 which was used as the input activity available to fill the small bowel. (b) A ROI was meticulously drawn in the terminal ileal reservoir region in the anterior (left) and posterior (right) views at 4 h to generate the decay corrected terminal ileal reservoir counts (kcounts/min) which were found to be 54.98. The index of small-bowel transit was derived to be 47%

Figure 2

Assessment of colonic transit using geometric mean method in a 50-year-old healthy control. Regions of interest (ROIs) were meticulously drawn encompassing the regions of cecum-ascending colon, transverse colon, descending colon, and rectosigmoid-anal canal in the anterior (a) and posterior (b) Images at 24 h. The eliminated counts (kcounts/min) at 24 h in this patient obtained by subtracting the total abdominal counts at 24 h from that of 4 h (as shown in Figure 1) was 49.77. Using these count values, the colonic geometric center was calculated to be 3.1. C-AC: Cecum-ascending colon, TC: Transverse colon, DC: Descending colon, RS-AC: Rectosigmoid-anal canal