Purpose or Case Report: Prenatal bowel dilation is often interpreted as an indicator of bowel pathology; however, it can be transient, leading to normal findings postnatally. This study aims to review cases of prenatal bowel dilation, analyze their sonographic findings, identify the most common diagnoses, and assess the concordance between prenatal and postnatal diagnoses.
Methods & Materials: This retrospective, IRB-approved study was conducted from March 2013 to March 2024. Variables included bowel diameter, amniotic fluid volume, bowel echogenicity, and subjective bowel wall thickness. The most likely prenatal diagnosis was recorded alongside any confirmed postnatal diagnosis of bowel dilation. A descriptive data analysis was performed, with a concordance evaluation to compare prenatal imaging findings with postnatal outcomes.
Results: A total of 101 fetuses with prenatal bowel dilation on ultrasound were reviewed. The mean bowel diameter on the prenatal scan was 12.3 mm (2.9-37.0 mm). Polyhydramnios was present in 78.0% (78) of cases; increased bowel echogenicity was present in 39.6% (40), and subjective bowel wall thickness in 18.8% (19). The most common prenatal diagnoses were gastroschisis (22.8%), small bowel atresia (15.8%), and meconium peritonitis (12.9%). Anal malformations were present in 9 (8.9%) cases. The concordance between prenatal and postnatal diagnoses was high for all conditions, ranging from 86.1% for small bowel atresia to 100% for congenital diaphragmatic hernia, gastroschisis, and omphalocele. However, postnatally, 28.7% (29) of the cases presented with normal bowel on abdominal radiographs despite prior prenatal suspicion of dilation. Among these, 20% (6 cases) demonstrated echogenic bowel, and 6.7% (2 cases) showed subjective thickening of the bowel walls. Amniotic fluid was normal in 73.3% (22) of these cases.
Conclusions: This study highlights the challenges associated with accurately diagnosing fetal bowel dilation using prenatal ultrasound. Although dilation can be detected using established normograms, our results reveal the risk of overdiagnosis. Additionally, bowel dilation alone is not a sufficiently specific finding. To enhance the specificity of postnatal diagnoses, it is essential to incorporate additional imaging findings. By evaluating these supplementary findings, fetal imagers can better differentiate between transient dilation and clinically significant pathologies, ultimately improving diagnostic accuracy and guiding appropriate management strategies for affected neonates.