E1880. The Role of Fetal MRI For Fetal Ventral Body Wall Defects
Fetal ventral body wall defects (VBWDs) are a complex and wide spectrum of congenital anomalies ranging from umbilical hernia to complex conditions like pentalogy of Cantrell. The overall prevalence rate is 6 cases per 10,000 births. All the related entities share the common feature of visceral herniation through a defect in the body wall; however, the clinical presentation, imaging findings, and coexistent congenital anomalies vary widely among the group. VBWDs at the severe of the end of the spectrum, like pentalogy of Cantrell, are usually fatal and require early termination of pregnancy. Gastroschisis and omphalocele, on the other hand, can be managed surgically; however, frequent association of omphalocele with chromosomal anomalies worsens the prognosis. Accurate location of the defect, its relation to the umbilical cord insertion, as well as exclusion of other structural anomalies is crucial for prenatal counseling and postnatal management. Prenatal ultrasonography (US) is the first line imaging tool employed, with VBWDs being detected in late first or early second trimester. Following a multidisciplinary team meeting, further evaluation with fetal MRI plays a crucial role in characterization of the VBWDs, depiction of associated visceral/structural abnormalities, and calculation of lung or herniated organ volume that are pivotal in prognostication and postnatal management.
Educational Goals / Teaching Points
We describe the epidemiological risk factors, occurrence, clinical presentation, prenatal and postnatal management as well as associated morbidity and mortality of various VBWDs. We elaborate the fetal MRI features of various VBWDs with the help of annotated and captioned fetal MR images. The fetal MRI protocol and the routine sequences employed for the procedure are also delineated. We briefly discuss the embryological pathogenesis behind the VBWDs with illustrations for a better understanding of the imaging findings on fetal MRI.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
VBWDs include entities like gastroschisis, omphalocele, bladder and cloacal exstrophy, body stalk anomaly/limb body wall complex, omphalocele-exstrophy of bladder-imperforate anus-spinal deformities complex (OEIS complex), pentalogy of Cantrell, amniotic band related abdominoschisis, and prune belly syndrome. During the 4th to 6th weeks of gestation, the embryo undergoes a combination of cranio-caudal and lateral folding responsible for converting the flat embryonic disc into a C-shaped structure, as well as creating the body cavity (future peritoneal space) and the gut tube. As the lateral folding continues, the lateral edges move further ventrally and ultimately fuse together, thus closing the abdominal wall. With the exception of omphalocele, most VBWDs involve varying degrees of failure of fusion of the lateral and cranio-caudal body folds.
VBWDs are an important cause of fetal morbidity and mortality, the correct diagnosis is imperative for prenatal counseling and management. Fetal MRI plays a pivotal role in detailed evaluation of the defect and coexistent structural anomalies, which is crucial for management.