A structured ultrasound approach for quantifying segmental terminal ileum motility: the terminal ileum motility index

Quantifying small-bowel motility remains challenging. We developed a structured cine-ultrasound protocol and introduced the Terminal Ileum Motility Index (TIMI), combining contraction frequency with fractional cross-sectional area reduction. In this prospective cross-sectional study, one operator examined 205 healthy adults after a 6–8-h fast. The terminal ileum was observed in a stable transverse plane for up to 20 min. After the first definite contraction, a 3-min active window was divided into three 1-min segments. Minute-specific TIMI equaled count multiplied by mean fractional amplitude from up to the first three contractions; final TIMI was their three-minute mean. In the full-cohort sensitivity analysis, participants without detected contractions had count and TIMI coded as zero and amplitude unestimated. Thirty-five randomly selected contraction-positive recordings were independently re-measured by both readers using the same predefined quantitative protocol, with each reader blinded to the other reader’s measurements. Two months later, each reader performed blinded exploratory 0–3 visual grading of these recordings plus 15 no-contraction recordings. The terminal ileum was technically evaluable in 182/205 participants (88.8%), and contractions were detected in 128/182 (70.3%). In the active-window cohort, mean amplitude, 3-min count, and TIMI were 54.55 ± 8.51%, 11.80 ± 4.40, and 2.10 ± 0.99. Full-cohort mean count and TIMI were 8.30 ± 6.54 and 1.48 ± 1.27. Count and amplitude were modestly correlated (ρ = 0.359), whereas TIMI correlated with count and amplitude (ρ = 0.945 and 0.603; all p < 0.001). Same-recording ICCs for amplitude, count, and TIMI were 0.837, 0.783, and 0.837. Inter-reader biases were small; count and TIMI showed proportional bias, with TIMI limits of agreement of − 0.929 to 0.947. Visual grading showed substantial ordinal agreement (linearly weighted κ = 0.718), and visual-score correlations with TIMI and count did not differ significantly. Structured cine ultrasonography enabled quantification of terminal ileal contractile activity and provided initial distributions in fasting healthy adults. TIMI integrated contraction frequency and deformation magnitude while preserving good same-recording inter-reader agreement. Although predominantly count-driven in this cohort, TIMI retained amplitude information and should be reported alongside its components. These findings establish a quantitative framework for multi-operator, test–retest, stimulus-response, independent-validation, and patient-cohort studies.