Magnetic resonance imaging of the fetal gallbladder and bile

To study the magnetic resonance imaging (MRI) appearance of the fetal gallbladder with special reference to fetal gallbladder sludge. In a retrospective study of 512 fetuses without gastrointestinal abnormalities, we classified the gallbladder MR appearances into patterns based on the signal intensity (SI) of bile on T1-weighted and T2-weighted sequences. We analysed the ratio of T1-weighted SI of bile. Maximum gallbladder width was correlated with gestational weeks (GW) using non-linear regression analysis and compared between various imaging patterns with one-way ANOVA. Five age-dependent patterns of the MRI appearance were found: (1) SI of bile was T2-weighted hyperintense and T1-weighted hypointense (78.5%); (2) presented with T2-weighted hyperintensity and T1-weighted signal isointense to liver (10.4%); (3) moderate hyperintense T2-weighted SI, T1-weighted SI hyperintense to liver (4.9%); (4) SI was T2-weighted isointense and T1-weighted hyperintense to liver (3.7%); (5) pronounced T2-weighted hypointensity and marked T1-weighted hyperintensity (2.5%). Pattern 1 was exclusively found before 27 GW, while patterns 2-5 increased in frequency after 30 GW. The MRI appearance of the fetal gallbladder is variable; fetal bile shows age-dependent SI changes that may cause non-visualisation of the gallbladder. This may be due to sludge and/or accumulation of paramagnetic substances suspended within gallbladder mucus.