What is the main characteristic of functional obstruction in meconium ileus?

The main characteristic of functional obstruction in meconium ileus is thick, tarry meconium. Meconium ileus occurs when the meconium, which is the first stool of an infant, becomes abnormally thick and sticky due to insufficient intestinal fluid production. This thick meconium leads to a blockage in the intestines, but it is not due to a structural abnormality; rather, it is a result of the functional aspect of how the intestines process and move the meconium.

In this condition, the viscous nature of the meconium prevents normal transit through the intestines, leading to symptoms of obstruction without an actual anatomical blockage. This characteristic can cause abdominal distension, feeding intolerance, and ultimately, complications if not addressed.

While fluid accumulation and abnormal motility are relevant in gastrointestinal conditions, they do not define the essence of a functional obstruction in meconium ileus as clearly as the nature of the meconium does. A complete blockage of the intestine suggests a more severe scenario than what is typically described in cases of meconium ileus. Thus, focusing on the quality of the meconium provides a more accurate understanding of the condition.