MRI features of fetal type I congenital choledochal cyst and parameter measurement of hepatobiliary development.

OBJECTIVES

To observe fetal MRI findings of type I congenital choledochal cyst (CCC) and the developmental differences in abdominal organs between fetuses with CCC and normal controls.

METHODS

This retrospective study included 90 normal fetuses and 31 fetuses with surgically confirmed CCC. MRI was used to observe CCC morphology, orientation, connection with bile duct or gallbladder, and its relationship with the liver edge. Cyst volume was calculated. Measurements, including the lung-to-liver signal intensity ratio (LLIR), liver (transverse and craniocaudal diameters, maximum cross-sectional area), spleen (long diameter, thickness, maximum cross-sectional area), gallbladder (long diameter, short diameter, maximum cross-sectional area), and portal vein diameter were compared between the two groups. Correlation between cyst volume and MRI parameters was analyzed.

RESULTS

Among the 31 CCC cases, 70.9% were female. The choledochal cyst morphology was elliptical in 26 cases. A "pointed apex sign" was observed in all cases. The inferior margin of the cyst did not extend beyond the inferior edge of the liver in 29 cases. The predominant orientation of the cyst was right upper to left lower in 26 cases. Compared to controls, CCC fetuses showed significantly larger splenic cross-sectional area, increased portal vein diameter, and higher gallbladder long-to-short diameter ratio (all P < 0.05).

CONCLUSION

CCC predominantly occurs in females. Fetal MRI findings typically show an elliptical lesion, generally not extending beyond the inferior edge of the liver, with a right upper to left lower orientation and a "pointed apex sign" at its superior margin. Affected fetuses exhibit an enlarged spleen, a widened portal vein, and an increased ratio of the gallbladder's long-to-short diameter. However, the cyst volume shows no correlation with these changes.