Diagnostic Performance of Antenatal Ultrasound in the Localization of Intestinal Structures Involved in Malrotation With a Higher-risk of Volvulus

Intestinal malrotation is a rare congenital anomaly resulting from abnormal rotation and fixation of the intestine during embryonic development. It is rarely asymptomatic and most often presents in the neonatal period with obstructive complications, including duodenal obstruction and, most critically, midgut volvulus. Midgut volvulus constitutes a surgical emergency due to the risk of extensive intestinal ischemia and necrosis, which may lead to short bowel syndrome or death.

Currently, there is no prenatal screening strategy for intestinal malrotation, and the feasibility and diagnostic performance of third-trimester obstetric ultrasound for detecting intestinal malrotation have never been formally evaluated.

Aim: To evaluate the diagnostic performance of third-trimester obstetric ultrasound in identifying the intestinal structures involved in high-risk intestinal malrotation associated with volvulus, using fetal MRI as the reference standard.

Methods : Eligible pregnant women will be identified during routine obstetric follow-up at Nîmes or Montpellier University Hospitals and enrolled exclusively in Montpellier. Each participant will undergo a third-trimester obstetric ultrasound and fetal MRI on the same day. Examinations will be performed independently by a senior obstetrician and a senior pediatric radiologist, both blinded to the other modality. Ultrasound visualization of mesenteric vessels, small bowel, and cecum will be compared with fetal MRI findings as the reference standard. Interobserver agreement for ultrasound interpretation will be assessed, and analyses will be stratified by gestational age. Participation duration is one day.