Does the transition zone reliably delineate aganglionic bowel in Hirschsprung's disease?

Background: Knowledge of the extent of aganglionic bowel is important for preoperative planning of trans-anal surgery in patients with Hirschsprung's disease (HD). Objective: To evaluate the accuracy of the transition zone, as identified by contrast enema study, for identifying the extent of aganglionic bowel. Materials and methods: A total of 32 patients with preoperative contrast enema studies and pathologic identification of aganglionic extent were reviewed. Two pediatric radiologists independently reviewed the contrast enema studies. The radiographic transition zone was compared to the pathological extent of aganglionic bowel. Results: Radiologist agreement of the site of transition zone on contrast enema was 90.6%. The concordance between the radiographic transition zone and pathologic extent of aganglionic bowel was 62.5%. The subgroup of patients with long-segment HD revealed a concordance of only 25%. Conclusion: Contrast enema delineation of the transition zone in HD needs to be regarded with caution. This is especially true in long-segment disease, where knowledge of the extent of aganglionic bowel is most crucial to surgical planning.