Purpose or Case Report: Differentiating levels of small bowel obstruction in the fetus and predicting the outcome remain challenging. Our goal is to characterize imaging details which suggest the level of obstruction or a potentially complex postnatal course.
Methods & Materials: A retrospective review of prenatal cases of small bowel obstruction imaged with MRI and US from 2005-2015 was conducted. Prenatal and postnatal imaging, surgical findings and long term outcomes were reviewed.
Results: 12 cases were identified, with 91% survival. Intraoperative and long term outcomes were available for 10. One fetus expired at 26 weeks and underwent autopsy. One fetus is not yet born. Gestational age at evaluation ranged from 25-36 weeks. 9/12 (75%) had polyhydramnios. 8/10 (80%) liveborn fetuses delivered prematurely. The level of obstruction was confirmed intraoperatively as jejunal in 9/11 (82%), ileal in 2/11 (18%). In 8/11 (73%) evaluated postnatally, intraoperative or autopsy findings were complex: multiple atresias (3), perforation (3), volvulus (1) and multiple anomalies including anal atresia (1). Cystic fibrosis (CF) was confirmed in 3/12 (25%). Fetal MRI signal characteristics of dilated small bowel loops correlated with obstruction level confirmed postnatally: in 5/11 low T1w dilated bowel loops corresponded to jejunal atresia, in 2/11 intermediate T1w signal bowel loops corresponded to distal jejunal atresia or complex perforation, and in 4/11 bright T1w signal in dilated bowel loops corresponded to CF, ileal atresia or concomitant anal atresia. The colon on T1w imaging was abnormally faint in all cases. Imaging of the rectum was similar in 8 cases of jejunal or ileal atresia irrespective of obstruction level, with adequate meconium distension. However, an abnormal paucity of rectal filling was noted in all cases of CF and in 1 case with concomitant high anal atresia. 3/11 (27%) developed short gut syndrome, 1 of which had perforation prenatally. The 2 postnatal cases of CF have had no further gastrointestinal complications.
Conclusions: Prenatal jejunal-ileal obstruction can have a variable outcome dependent on etiology, coexisting abnormalities such as CF and number of atresias. Complications may include volvulus, perforation, and preterm delivery. Fetal MRI is useful in the more complex atresias for assessment of meconium distribution within the small bowel, colon and rectosigmoid.