Additive value of fetal MRI to different ultrasound modalities in diagnosis of fetal GIT and abdominal wall anomalies
Authors: Abbas Hoda Magdy , Hamed Soha Talaat , Gaafar Hassan Mostafa , Amer Maha Mohammed , Sayed Safia Badr 
Published: March 2023

Abstract
Background
Fetal MRI is a valuable supplementary study to the prenatal US in accurate diagnosis of fetal gastrointestinal anomalies and ventral abdominal wall anomalies, which has an impact on the postnatal outcome.

Aim of work
To establish the additive role of fetal MRI to the prenatal US in the identification of complex fetal GIT anomalies.

Methods
This prospective study involved 36 pregnant patients with age range from 19 to 41 years (mean ± SD of 27.8 ± 5.3 years). Thirty-six fetuses (19 males and 17 females). All cases underwent dedicated 2D obstetric ultrasound assessment with a focus on the fetal abdomen and some cases required additional 3D and 4D assessment. Twenty-seven patients underwent fetal MRI procedures.

Results
In our study, fetal MRI was significantly more accurate than US in the confirmation and accurate delineation of the level of small bowel obstruction and differentiation of complete obstruction from luminal stenosis. In cases of anorectal malformations, prenatal US and fetal MRI were equally sensitive in the detection of their associated findings. While fetal MRI was superior to the US in the case of congenital chloride diarrhea. MRI images added the presence of distended oropharynx in esophageal atresia cases while other findings were detected with the same accuracy with both US and MRI. In cases of ventral abdominal wall defects, fetal MRI added fine details about the true size of the defect, the actual content of the abdominal wall defect as well as the detection of the presence of large bowel loops and related complications. In the category of fetal abdominal cysts, fetal MRI was superior to the US owing to its greater soft tissue characterization. In the case of sacrococcygeal teratoma (SCT), fetal MRI detected an additional intra-pelvic extension upgrading the tumor and detecting the true size of the intra-spinal component. In the category of congenital diaphragmatic hernia, MRI was superior in the detection of hernia capsule, herniated liver, and associated complications as well as accurate estimation of fetal lung volume. Studying the cases of cloacal malformations showed that owing to better tissue characterization by MRI the anomaly and its associated abnormal genitourinary communication were better delineated by MRI. The sensitivity of MRI to detect congenital anomalies concerning postnatal findings was 100%, the specificity was 50% and diagnostic accuracy was 96.6%. The sensitivity of ultrasound to detect congenital anomalies concerning postnatal findings was 85.3%, the specificity was 89%, and diagnostic accuracy was 80.6%. The sensitivity of combined US and MRI to detect congenital anomalies concerning postnatal findings was 100%, the specificity was 89%, and diagnostic accuracy was 93.1%.

Conclusions
Fetal MRI is a valuable supplementary study to the prenatal US in accurate diagnosis of fetal obstructive gastrointestinal anomalies, ventral abdominal wall anomalies, fetal abdominal cysts, masses, and congenital diaphragmatic hernia. Fetal MRI is equally sensitive to the prenatal US in anorectal malformations.