transition zone
Bowel segment between normal ganglionic intestine and aganglionic bowel in Hirschsprung disease, often showing irregular caliber.
Full Definition
The transition zone in Hirschsprung disease represents the bowel segment between normally innervated (ganglionic) intestine and the aganglionic segment. This area is characterized by irregular bowel caliber changes and may show histological features that are intermediate between normal and completely aganglionic bowel. Radiologically, the transition zone appears as an area of irregular narrowing or funnel-shaped tapering on contrast studies. Surgical planning must account for the transition zone, as complete resection of aganglionic bowel requires extending the resection beyond this area to ensure anastomosis to normally innervated bowel.
Usage
Usage note: Two words, not hyphenated; refers specifically to Hirschsprung disease context.
In Context
- "The transition zone was identified radiographically at the sigmoid level." — Radiology report
- "Frozen section biopsies confirmed normal ganglion cells proximal to the transition zone." — Operative report