Early MRI findings of small bowel obstruction: an experimental study in rats

Purpose: This study was undertaken to identify the early magnetic resonance imaging (MRI) findings of small bowel obstruction (SBO) and to analyse their evolution over time comparing them with histological findings. Materials and methods: SBO was surgically induced in 10 rats divided into two groups monitored at predetermined time points until the 8th hour: group 1, macroscopically observed and group 2, investigated with 7-Tesla micro-MRI (7 T μ-MR). At the end of observation, the bowel was excised for histological analysis. Results: 7 T μ-MRI T2-w sequences acquired 15 min after SBO, showed early evidence of bowel wall hyperintensity and a small amount of peritoneal free fluid. At 1 h, a hyperintensity of the loop proximal to the obstruction was found and, after 4 h, free fluid between the loops, bowel wall thickening and increased wall hyperintensity were also found. After 6 h hypotonic reflex ileus (only gas-filled dilated loops) was detected, which became paralytic ileus (dilation with air-fluid levels) after 8 h. The MRI findings were all confirmed at histological examination. Conclusions: This study allows definition of the early MRI features of SBO (peritoneal free fluid and hyperintensity of the injured bowel) and their chronological evolution, also confirmed by histological examination. Our data suggest a potential role of MR imaging in the early diagnostic assessment and management of patients with SBO. The chance to achieve an early detection of bowel injury and to correlate the histological pattern with imaging findings could contribute to a finer and earlier diagnosis and a more effective treatment.