Echo-Planar Magnetic Resonance Imaging to Assess Water Volume in the Distal Small Bowel

Purpose. Assessment of fluid volumes and flow through the small intestine has in the past only been possible by means of invasive intubation studies on human volunteers. Intubation very likely disturbs gut motility and stimulates secretion. Methods. The aim of this study was to utilise the new technique of echo-planar magnetic resonance imaging in order to non-invasively visualise the changing volume of water in the small intestinal lumen. 200mls of test solution was ingested and water volume assessed using a multi-slice scanning technique on 3 separate days. The solutions were pure water, pure water plus 2.264 or l0g of mannitol. These were taken on separate days by 8 healthy male volunteers. Regions of interest were constructed in the area of the lower pelvis excluding retroperitoneal structures. Results. The water content of the lower small intestine did not change significantly over the 4 hours after the control solution. By contrast after both mannitol solutions there was an increase in the amount of water in the distal intestine as assessed by the area under the curve of the volume time profile (Control 51 ml.h (SD ±47); mannitol 2.264g/200ml 72ml.h (SD ±57); 10g/200ml mannitol 115ml.h (SD ±56)). Page's L Trend test showed that the trend for the volume to increase with increasing mannitol concentration to be statistically significant at the 1% level (L= 108). Conclusions. The study highlights the potential of echo-planar magnetic resonance imaging to visualise changes in gastrointestinal physiology in a non-invasive manner.