Measurement of oro-caecal transit time by magnetic resonance imaging

Objectives: To assess prospectively the agreement of orocaecal transit time (OCTT) measurements by lactulose hydrogen breath test (LHBT) and magnetic resonance imaging (MRI) in healthy subjects. Methods: Volunteers underwent abdominal 1.5-T MRI using axial and coronal single-shot fast-spin-echo T2-weighted sequences, having fasted and after lactulose ingestion (10 g/125 mL). Imaging and H₂ excretion gas-chromatography were performed concurrently every 15 min up to 180 min. MR images were analyzed using semiautomatic segmentation to calculate small bowel gas volume (SBGV) and visually to detect bolus arrival in the caecum. Agreement between MRI- and LHBT-OCTT was assessed. Results: Twenty-eight subjects (17 men/11 women; mean age ± standard deviation 30 ± 8 years) were evaluated. Two H₂ non-producers on LHBT were excluded. OCTT measured by MRI and LHBT was concordant in 18/26 (69 %) subjects (excellent agreement, k = 0.924). Median SBGV was 49.0 mL (interquartile interval 44.1 – 51.6 mL). In 8/26 (31 %) subjects, MRI showed that the lactulose bolus was in the terminal ileum and not the caecum when H₂E increased on LHBT. Median OCTT measured by MRI was significantly longer than OCTT measured by LHBT [135 min (120 – 150 min) vs. 127.5 min (105 – 150 min); p = 0.008]. Above baseline levels, correlation between [H₂] and SBGV was significant (r = 0.964; p <0.001). Conclusions: MRI provides valid measurements of OCTT and gas production in the small bowel. Key Points: • MRI is a valid technique to measure OCTT. • Excellent agreement between MRI and LHBT was found. • Measuring gas production using MRI may provide evidence of small bowel fermentation.