Prenatal diagnosis of tracheo-oesophageal fistula/oesophageal atresia: is MRI helpful?

Background

Oesophageal atresia (OA) with or without tracheo-oesophageal fistula (TOF) affects 2.75 per 10,000 births within the UK. It is most frequently suspected on antenatal imaging when the stomach is absent or appears small. Studies have shown fetal magnetic resonance imaging (MRI) has greater diagnostic accuracy than ultrasound; however, there remains uncertainty over what size constitutes a small stomach and how frequently this correlates with a diagnosis of TOF/OA.

Methods

A retrospective study of patients referred for fetal MRI due to suspicions of TOF/OA on antenatal ultrasound from 2011 to 2022. We also included patients with a fetal MRI suspecting TOF/OA who had been referred for other reasons. The indication, MRI findings and postnatal outcome were compared to assess diagnostic accuracy. For each case, the size of the stomach bubble was measured on MRI, and stomach volumes in a control group were measured for comparison.

Results

The positive predictive value for USS was 45.5% and 51.7% for fetal MRI. Fetal MRI had a negative predictive value and sensitivity of 100% (p = 0.027). The control group showed a strong positive correlation between stomach size and increasing gestational age (R2 = 0.69, p < 0.001), but this correlation was less positive in the TOF/OA group (R2 = 0.26, p = 0.03), and the stomach volumes in TOF/OA were consistently lower than the control group. The receiver operating characteristic curve illustrates that an absent stomach or unmeasurably small stomach is more diagnostic of TOF/OA as volumes ≤0.06 ml had 90% sensitivity.

Conclusion

Fetal MRI can accurately exclude TOF/OA but only has marginally improved positive predictive value over ultrasound. Research with larger numbers is required to further aid the development of a cut-off value for what can be considered a pathologically small stomach.

Impact

There are several features on imaging that raise the suspicion of TOF/OA.

Fetal MRI has some improved diagnostic accuracy compared with antenatal ultrasound alone; however, it is only marginally better.

Absence of stomach bubble and presence of oesophageal dilatation combined on fetal MRI are more diagnostic of TOF/OA.