## **Core Concept**
The question tests knowledge of neonatal gastrointestinal conditions, specifically those leading to colonic obstruction. Colonic obstruction in neonates can result from various causes, including anatomical abnormalities, functional issues, or other pathological conditions.

## **Why the Correct Answer is Right**
The correct answer, **C. Hirschsprung's disease**, is the most common cause of colonic obstruction in neonates. Hirschsprung's disease is a congenital condition characterized by the absence of ganglion cells in the distal bowel, leading to a functional obstruction. This condition typically presents in the neonatal period with symptoms such as abdominal distension, vomiting, and failure to pass meconium within the first 48 hours of life.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While intestinal atresia can cause obstruction, it is more commonly associated with small intestinal obstruction rather than colonic obstruction specifically.
- **Option B:** This option is not specified, but if it were another condition, it would not be the most common cause of colonic obstruction in neonates.
- **Option D:** Other causes like meconium ileus (associated with cystic fibrosis) can cause intestinal obstruction but are less common causes of colonic obstruction compared to Hirschsprung's disease.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Hirschsprung's disease often presents with a history of delayed passage of meconium (>48 hours after birth) and abdominal distension. A rectal biopsy is diagnostic, showing an absence of ganglion cells.

## **Correct Answer:** . Hirschsprung's disease