The Value Of MRI In The Diagnosis Of Fetal Digestive Tract Deformity And Obstruction

Objective To explore the advantages of MRI in the diagnosis of fetal digestive tract deformity and obstruction and to provide guidance for antenatal consultation.Methods 34 cases of pregnant women whose baby were suspected abnormality of digestive tract were analyzed retrospectively.All the pregnant women underwent examination from March 2014 to June 2019.One or more signs were discovered by ultrasound such as polyhydramnios,blind bag dilatation in the upper esophagus,small or unmanifested gastric vesicles,etc and ultrasound suspected gastrointestinal dilatation and intestinal obstruction.MRI examination was performed within 4 days after ultrasound.Using Philips 1.5T superconducting MRI instrument.Single-shot turbo spin-echo(SSTSE)sequence,balanced fast field echo(BFFE)sequence and T1 WI sequence were used for scanning and diffusion weighted imaging(DWI)sequence scanning was performed if necessary.Axial,coronal and sagittal scanning were all performed.Cases suspected of esophageal atresia often needed repeated scans to show the filling of esophagus and gastric vesicles.Cases of intestinal obstruction underwent fetal total abdominal scan to evaluate the situation of the whole gastrointestinal tract.The results of antenatal ultrasound,antenatal MRI,postmortem examination and operation pathology were compared and analyzed.Results In all cases,7 cases were diagnosed as esophageal atresia after birth or autopsies.6 cases were diagnosed as esophageal atresia by MRI.One case that the gastric vesicle was slightly smaller,the esophagus was not clear,and the amniotic fluid volume was roughly normal showed by MRI was misdiagnosed.MRI showed blind bagdilatation in the upper segment of esophagus in 4 cases.2 cases were normal after birth.Prenatal ultrasound showed that the gastric vesicles were small,but the continuity of esophagus was confirmed by MRI.There were 25 cases of fetal intestinal obstruction,including 4 cases of membranous stenosis of duodenal and 4 cases of membranous stenosis of jejunum,with "wind pocket sign" and low signal intensity on T1 WI of bowel proximal to the obstruction,and the distal bowel was slightly smaller and the rectum was normal.High signal intensity on T1 WI of bowel distal to the obstruction in 6 cases of jejunal atresia and ileal atresia.Rectal atresia was found in 2 cases.The end of rectum was on the high side,locating above the neck of the bladder.Among them,1 case was complicated with horseshoe kidney malformation and low conus medullaris,which could be diagnosed as VACTERL malformation,and 1 case was complicated with sacral and coccyx hypoplasia.Intestinal malrotation was found in 4 cases.The axial SSTSE sequence of MRI showed that the upper and middle abdominal bowels rotated The obstructed bowels showed "beak-like" stenosis.The dilated bowels showed low signal intensity in T1 WI and high signal intensity in T2 WI."Whirlpool sign" was seen in the middle abdomen enhanced by CT after birth.That was,the superior mesenteric vein rotated around the superior mesenteric artery.Among them,2 cases were intestinal malrotation complicated with duodenal membranous stenosis.Annular pancreas was seen in 4 cases,MRI showed dilatation of the proximal segment of the stomach and duodenum,showing a "double bubble sign" of high signal intensity of T2 WI sequence and low signal intensity of T1 WI sequence.The pancreas around the descending part of the duodenum surrounded the duodenum in a circular or clamp shape,and the intestinal canal at the obstruction was "beak-like" stenosis.The distal small bowel,colon and rectum were generally normal.Intestinal volvulus was seen in 2 cases.Meconium peritonitis was secondary to Intestinal volvulus."Whirlpool sign" was seen in the middle and lower abdomen and "beak-like" stenosis was found at the end of obstruction.The dilated bowel showed uneven high signal intensity of T1 WI.DWI sequenceshowed heterogeneous mixed high signal intensity in the intestinal wall and lumen of the lesion area,and 2 cases were complicated with celiac effusion.In 1 case of intussusception,"concentric circle sign" was seen,and diffuse T1 WI high signal filling was found in the small intestine and colorectal cavity.Conclusion MRI is of high value in diagnosis of fetal digestive tract deformity and obstruction.It can be used as an effective supplementary method for antenatal ultrasound and has important guiding significance for antenatal consultation and postpartum surgery.