Fetal MR in the evaluation of pulmonary and digestive system pathology

Abstract

Background: Prenatal awareness of an anomaly ensures better management of the pregnant patient, enables medical teams and parents to prepare for the delivery, and is very useful for making decisions about postnatal treatment. Congenital malformations of the thorax, abdomen, and gastrointestinal tract are common. As various organs can be affected, accurate location and morphological characterization are important for accurate diagnosis.

Methods: Magnetic resonance imaging (MRI) enables excellent discrimination among tissues, making it a useful adjunct to ultrasonography (US) in the study of fetal morphology and pathology.

Results: MRI is most useful when US has detected or suspected anomalies, and more anomalies are detected when MRI and US findings are assessed together.

Conclusion: We describe the normal appearance of fetal thoracic, abdominal, and gastrointestinal structures on MRI, and we discuss the most common anomalies involving these structures and the role of MRI in their study.

Teaching points: • To learn about the normal anatomy of the fetal chest, abdomen, and GI tract on MRI. • To recognize the MR appearance of congenital anomalies of the lungs and the digestive system. • To understand the value of MRI when compared to US in assessing fetal anomalies.

Fig. 1

Normal fetal anatomy of the thoracoabdominal region. Fetus at 28 weeks’ gestation. a, b and c Fetal axial, sagittal, and coronal single-shot fast spin-echo MR images showing some normal fetal structures: h heart, L lungs, t thymus, and li liver. The trachea and bronchi are seen as hyperintense tubular structures in (c)

Fig. 2

Normal fetal anatomy of the thoracoabdominal region. Fetus at 26 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image showing many fetal structures: lungs (asterisk), stomach (long arrow), small intestine (short arrows), liver (curved arrow), and gallbladder (arrowhead). b Coronal T1-weighted gradient-echo FLASH sequence showing the stomach (long arrow), large intestine (arrowheads), and liver (curved arrow)

Fig. 3

Left congenital diaphragmatic hernia. Fetus at 27 weeks’ gestation. a Coronal image of the fetal chest and abdomen. Elevation of the left diaphragm (long arrow); we can see the fetal stomach full of fluid (short arrow). b X-ray after birth shows the same findings

Fig. 4

Right congenital diaphragmatic hernia. Fetus at 36 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image and b T1-weighted fetal coronal image show the diaphragmatic hernia. Part of the liver (short arrow) is in the chest and the heart (long arrow) is displaced slightly to the left. c Fetal axial single-shot fast spin-echo MR image shows part of the liver (short arrow) in the chest and the leftward shift of the heart (long arrow). d X-ray after birth

Fig. 5

Congenital cystic adenomatoid malformation. Fetus at 22 weeks’ gestation. a, b and c Fetal sagittal, coronal, and axial single-shot fast spin-echo MR images of the fetal chest show a complex hyperintense lesion with cysts inside in the right lung (arrows). CT after birth d shows the lesion, which is proportionally smaller than in the MR images

Fig. 6

Extralobar bronchopulmonary sequestration. Fetus at 23 weeks’ gestation. a, b and c Fetal coronal, sagittal, and axial single-shot fast spin-echo MR images of the fetal chest show a hyperintense anomalous area in the left lung (arrows). d, c and f CT after birth shows bronchopulmonary sequestration (white arrows) and the systemic vessel (black arrows) that feeds the lesion

Fig. 7

Infradiaphragmatic extralobar pulmonary sequestration. Fetus at 23 weeks’ gestation. a Fetal sagittal single-shot fast spin-echo MR image showing a well-defined hyperintense mass with hypointense septa in the left abdomen (arrow) between the diaphragm, the stomach (arrowhead), and above the kidney. Imaging studies after birth (US, CT, and MR) detected this lesion; the suprarenal gland was normal and the metaiodobenzylguandine study was negative. b Postnatal axial T1-weighted MR image showing the lesion (arrows). The child is asymptomatic, and the laboratory tests were normal. No anomalous vascular irrigation was detected; nevertheless, we believe this is a case of infradiaphragmatic extralobar pulmonary sequestration, and no surgery has been performed

Fig. 8

Esophageal atresia with distal tracheoesophageal fistula. Fetus at 33 weeks’ gestation. MR was indicated for US findings of renal ectopia or horseshoe kidney. a and b Sagittal single-shot fast spin-echo MR images of the fetus. MR detected left renal agenesis and ectopia of the right kidney (arrow in a). A pouch was detected in the upper esophagus (arrow in b). There was polyhydramnios, and the stomach was small. c and d CT after birth showing the atresia and the tracheoesophageal fistula (arrow in d), T trachea, E esophagus

Fig. 9

Duodenal stenosis due to Ladd’s band. Fetus at 32 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image: the duodenum is greatly dilated until the third portion (short arrow); the stomach seems normal; there may be gastroesophageal reflux. The volume of amniotic fluid is normal. The large bowel is in the left abdomen (long arrows). b X-rays after birth showing marked dilatation of the duodenum. At surgery, intestinal malrotation and Ladd’s band causing duodenal occlusion were found, as well as Meckel’s diverticulum, which was undetected at US and MR

Fig. 10

Jejunal atresia. Fetus at 25 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image and b fetal coronal T1-weighted gradient-echo flash image showing dilatation of the proximal portion of the small intestine (arrows). c X-ray after birth showing dilatation of the proximal intestinal loops. Opaque enema X-ray study showed microcolon, and jejunal atresia was discovered at surgery

Fig. 11

Meconium peritonitis. Fetus at 26 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image showing a small amount of ascites (short arrow) and dilatation of intestinal loops (long arrow); a small hypointense area is seen in the left hemiabdomen (arrowhead), suggestive of peritoneal calcification. b CT after birth shows peritoneal calcifications and a meconium pseudocyst (arrows)

Fig. 12

Cecal atresia. Fetus at 22 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image and b fetal coronal T1-weighted gradient-echo flash image. In the right hemiabdomen, below the liver there is a dilated bowel loop hypointense on T2- and hyperintense on T1-weighted images (arrows), due to meconium. c Abdominal X-ray after birth shows a dilated bowel loop. d At surgery cecal atresia was found

Fig. 13

Heterotaxy syndrome, polysplenia syndrome. Fetus at 20 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image in which the liver (arrows) and stomach (arrowhead) are centrally located; the multiple spleens present were not seen at MR. b Anatomical specimen showing these anomalies: liver (arrows), stomach (arrowhead). This fetus had heart defects

Fig. 14

Heterotaxy syndrome, situs inversus. Fetus at 23 weeks’ gestation. a and b Fetal coronal single-shot fast spin-echo MR images: the heart is in the correct position (arrow in a) but the stomach is on the right side of the abdomen (arrow in b). c Barium studies after birth confirm this anomaly

Fig. 15

Intestinal duplication. Fetus at 24 weeks' gestation. a Fetal sagittal single-shot fast spin-echo MR image: a hyperintense structure (long arrow) is seen above the bladder (short arrow); in T1-weighted sequences this lesion was hypointense. The rest of the intestinal loops were normal at MR, but intestinal occlusion with marked dilatation of the intestinal loops was present at birth. Surgical intervention discovered intestinal duplication (b). Intestinal duplication caused volvulus of the small intestine

Fig. 16

Ovarian cyst. Fetus at 36 weeks’ gestation. a Fetal coronal and b axial single-shot fast spin-echo MR images showing a rounded hyperintense structure (arrow) occupying a large part of the left hemiabdomen, with fluid-fluid level in its interior (arrowheads in b). c CT at 4 months of age: the lesion is now located on the right side and shows calcification of the wall (arrow). US follow-up shows complete disappearance of the cyst and also of the right ovary

Fig. 17

Hepatic cyst. Fetus at 17 weeks’ gestation. a Fetal sagittal single-shot fast spin-echo MR image showing a cystic lesion of the liver (arrow). This fetus also had agenesis of the right kidney, dysplasia of the left kidney, and heart defects. b The hepatic cyst (arrow) can be seen in the pathological specimen

Fig. 18

Neuroblastoma. Fetus at 36 weeks’ gestation. a Fetal coronal single-shot fast spin-echo MR image showing a well-delimited, slightly heterogeneous infradiaphragmatic mass of intermediate signal intensity (arrow) located above the right kidney, which is displaced downward (curved arrow). b Metaiodobenzylguandine study after birth was positive (arrow)

Fig. 19

Gastroschisis. Fetus at 19 weeks’ gestation. a Fetal axial single-shot fast spin-echo MR image showing a large portion of the intestinal loops outside the abdominal cavity (arrowhead). There is no peritoneal lining, and the umbilical cord is inserted in the correct position (arrow). The liver and the stomach are within the abdomen. b Photograph of the patient after birth showing the intestinal loops outside of the abdominal cavity and the umbilical cord (arrow) inserted in the correct position

Fig. 20

Omphalocele. Fetus at 21 weeks’ gestation. a Fetal axial single-shot fast spin-echo MR image shows the bowel loops lined with peritoneal membranes (arrow) outside the abdominal cavity. b Volumetric T2 images are useful to identify the umbilical cord (arrow). c Photograph of the patient after birth showing the intestinal loops outside of the abdominal cavity, the peritoneal membranes, and the position of the umbilical cord (arrow)