Is Meconium Obstruction Distinguishable from Intestinal Obstruction through Ultrasound?

Background: Since the treatment of meconium ileus is very different from other types of intestinal obstruction, it is very important to distinguish these two entities. The aim of this study was to assess sonographic findings to differentiate meconium ileus from other types of obstruction. Methods: This study was performed in Dr. Sheikh and Akbar hospitals, Mashhad Medical University of Science, Iran, during 2017- 2018. The imaging signs of 25 newborns (aged 2-8 days) with delayed passage of meconium were documented. These neonates were suspicious of low type intestinal obstruction. In cases with the simple form of meconium ileus and the small left colon syndrome, ultrasonic guided Gastrografin enema was performed for the treatment. In the patients with the failure of medical treatment and in other surgical cases, the appropriate surgical procedure was performed. Results: The subjects in this study were diagnosed with small bowel atresia (n=9), a simple form of meconium ileus (n=6), a complicated form of meconium ileus (n=3), small left colon syndrome (n=3), bowel atresia and duplication (n=1), and Hirschsprung’s disease (n=3). The ultrasound findings were as follows: a totally or partially micro-colon in almost all patients, collapsed small bowel in right lower quadrant in all of the patients with bowel atresia, hypoechoic meconium in rectosigmoid in small left colon syndrome and Hirschsprung’s disease, hypoechoic tubular or beaded intraluminal inspissated meconium within terminal ileum, and the floating air bubbles (sonographic soap bubble sign) within fluids on proximal dilated loops in meconium ileus cases. Conclusion: Although plain abdominal radiography confirmed bowel obstructions in all patients with delayed passage of meconium, it had a low level of specificity in the diagnosis and cause of obstruction.  Abdominal ultrasound had a high level of accuracy in the correct diagnosis of meconium obstructions and its differentiation from other intestinal obstructions. Accordingly, it eliminates the need to do a diagnostic contrast enema in order to differentiate these entities.