Growth of the colon and rectum throughout gestation: evaluation with fetal MRI.

Background: Congenital abnormalities of the gastrointestinal tract are increasingly being evaluated by prenatal magnetic resonance imaging (MRI). However, there is a paucity of reports describing the normal quantitative development of the fetal colon and rectum on MRI.

Purpose: To provide growth curves of the MRI estimated diameter of the fetal colon and rectum as a function of gestational age.

Material And Methods: This is a retrospective review of 191 singleton fetal MRI studies at 25-39 weeks of gestation. Measurements included maximal diameter of the ascending, transverse, and descending colon on coronal and sagittal views, maximal diameter of the rectum on coronal and sagittal views, and maximal diameter of the rectum at the level of the bladder base on sagittal views. Median growth curves were built using a generalized additive model. Confidence regions were built for 10th, 25th, 75th, and 90th percentiles.

Results: Smoothed growth curves for the median, and one and three quartiles for each of the five sections as a function of gestational age were calculated. All graphs had a slightly exponential curve.

Conclusion: This study provides normal ranges of the prenatal colon and rectum as a function of gestational age. They may serve as reference values when interpreting fetal MRI.