Referral for Dilated Fetal Rectum: Rarely a Pathologic Entity

Area of Science:

• Fetal Medicine
• Pediatric Surgery
• Diagnostic Imaging

Background:

• Dilated fetal colon or rectum on prenatal imaging can suggest anorectal malformation (ARM) or Hirschsprung's disease (HD).
• Accurate prenatal diagnosis is crucial for timely intervention and improved neonatal outcomes.

Purpose of the Study:

• To evaluate the association between fetal rectal/colonic dilation on ultrasound (US) and magnetic resonance imaging (MRI) and postnatal distal bowel abnormalities.
• To develop a risk score for diagnosing anorectal malformation (ARM) based on specific fetal imaging findings.

Main Methods:

• Retrospective analysis of pregnant women referred for suspected fetal rectal/colonic dilation between 2006-2024.
• Comparison of fetal US and MRI findings with neonatal outcomes.
• Univariate analysis to identify significant predictors of postnatal distal bowel abnormality and formulate a risk score.

Main Results:

• 38.2% of patients had normal imaging; 61.7% showed persistent fetal colon/rectum prominence or dilation.
• Seven male fetuses with large bowel dilation were diagnosed with imperforate anus; none had Hirschsprung's disease (HD).
• A risk score incorporating 8 variables demonstrated 100% sensitivity and specificity for diagnosing ARM in the cohort.

Conclusions:

• Fetal imaging findings of a dilated colon/rectum are infrequently associated with pathology.
• When targeted fetal imaging lacks predictive features of pathology, families and providers can be reassured.
• The developed risk score aids in the accurate prenatal diagnosis of anorectal malformation.