What is a significant distinguishing feature of the colon in patients with Hirschsprung disease?

In Hirschsprung disease, a significant distinguishing feature of the colon is the presence of a proximal dilated colon. This condition results from a lack of ganglion cells (neurons) in the submucosal and myenteric plexuses of the bowel, leading to an inability to relax the affected segment of the colon. The segment lacking ganglion cells, known as the aganglionic segment, causes a blockage of stool passage. As a result, the distal end of the colon that is still functional (proximal to the affected segment) becomes hypertrophied and distended due to prolonged accumulation of fecal matter, which leads to dilation.

This proximal dilation is a hallmark of the condition because it reflects the functional obstruction caused by the absence of enteric neurons in the aganglionic segment and indicates how the normal peristalsis and bowel dynamics are disrupted. Identifying this proximal dilation in imaging studies is crucial in diagnosing Hirschsprung disease, as it reveals the consequences of the condition's pathophysiology.

In contrast, a narrow, underdeveloped colon would not accurately reflect the nature of the obstruction or the dilation seen in Hirschsprung disease, melanosis coli relates to a different condition associated with laxative use