Hydrophilic Polymers Enable Gastrointestinal Transit Monitoring by Fluorine-19 Magnetic Resonance Imaging.

Gastrointestinal (GI) transit shapes nutrient absorption and oral drug delivery. However, GI anatomy, function, and motility disorders are primarily examined by radiographic imaging, which exposes patients to ionizing radiation and yields only coarse proxies of how a meal moves through the gut. By contrast, fluorine-19 (19F) MRI offers background-free, quantitative tracking, but most oral 19F agents are hydrophobic and phase-separate from chyme, generating layering artifacts, which spoil motility and anatomy readouts. Here, we developed nonresorbable, hydrophilic fluorinated polymer tracers miscible with luminal contents. These tracers provided a strong, quantifiable 19F signal for combined 1H/19F MRI and 19F spectroscopy, enabling us to visualize GI anatomy and transit noninvasively. In vivo imaging reliably tracked whole-gut transit and fecal elimination, with no evidence of systemic uptake or tissue injury. As such, this practical, reproducible, and radiation-free platform for phenotyping dysmotility and monitoring therapeutic response may open up opportunities for longitudinal GI studies and clinical trials.