## Core Concept
Congenital megacolon, also known as Hirschsprung's disease, is a condition characterized by the absence of ganglion cells in the distal bowel, leading to a functional obstruction. The underlying issue is the failure of neural crest cells to migrate to the distal bowel during fetal development.

## Why the Correct Answer is Right
The correct answer is related to the characteristics of Hirschsprung's disease. Typically, this condition presents with a narrowed aganglionic segment of colon and a dilated segment proximal to it. The disease is associated with the absence of ganglion cells (aganglionosis) in the affected segment of the colon.

## Why Each Wrong Option is Incorrect
- **Option A:** Not provided, so cannot assess.
- **Option B:** Not provided, so cannot assess.
- **Option C:** Not provided, so cannot assess.
- **Option D:** Not provided, so cannot assess.

## Clinical Pearl / High-Yield Fact
A key clinical pearl for Hirschsprung's disease is that it often presents in infancy with symptoms such as constipation, abdominal distension, and vomiting. A definitive diagnosis is made by rectal biopsy showing the absence of ganglion cells.

## Correct Answer: D.