**Core Concept:** Hirschsprung disease is a congenital disorder characterized by the absence of ganglion cells in the distal gut, leading to impaired intestinal motility and distension. The condition presents in neonates with failure to pass meconium, abdominal distension, and ineffective peristalsis.

**Why the Correct Answer is Right:** Hirschsprung disease results from the absence of ganglion cells in the distal gut, particularly involving the rectosigmoid colon and rectum. This absence leads to impaired intestinal motility and distension, eventually causing the symptoms observed in the presented scenario.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because the cause of Hirschsprung disease is not related to the presence or absence of ganglion cells in the colon.

B. This option is incorrect as Hirschsprung disease is not caused by a narrow conical segment and dilated proximal bowel on radiological imaging. These findings are a result of the disease, not its cause.

C. This option is incorrect because the cause of Hirschsprung disease is not related to the symptoms or imaging findings, which are secondary to the disease itself.

D. This option is incorrect as the cause of Hirschsprung disease is not related to the newborn's age, but rather the absence of ganglion cells in the distal gut.

**Clinical Pearl:** Hirschsprung disease is a crucial diagnosis to make in neonates presenting with abdominal distension, failure to pass meconium, and ineffective peristalsis. Prompt diagnosis and management are essential for preventing complications like megacolon and ensuring proper intestinal motility.