Background: The goal of surgical management for Hirschsprung disease is resection of the affected aganglionic bowel. Determining the level of aganglionosis is very important for transanal endorectal-pullthrough.
Objective: The aim of this study was to determine the accuracy of intra-operative finding transitional zone compared to the
radiologic transitional zone and the histological extent of aganglionic bowel.
Material and Method: Twenty-six children with underlying Hirschsprung disease, operated at the pediatric surgery unit,
Siriraj Hospital, during the period from August 2012 to September 2015 were included in this prospective study. Patients with colostomy and those underwent Redo pullthrough were excluded. Pre-operative contrast studies were identified for radiologic transitional zone in standard anatomic sectors (rectum, recto-sigmoid, descending, splenic flexor, transverse, hepatic flexor, ascending colon). The operative transitional zone was identified and full thickness colonic tissue samples were sent for histological examination from transitional zone and every 2 centimeters proximal to transitional zone until the ganglionosis was found. The radiologic transitional zones were correlated to operative findings and compared to the pathological extent of aganglionic bowel.
Results: Twenty-one cases of short segment and 5 cases of long segment Hirschsprung disease showed correspondence of
radiologic and operative transitional zone. Only 4 cases were proved by frozen section that the operative transitional zone
was the level of ganglionosis, whereas the other 22 found that the level of ganglionosis were more proximal. All of the true
ganglionic segments were located within 10 centimeters proximal to the operative transitional zone.
Conclusion: The operative transitional zone consistently correlated with radiologic information while the true ganglionic
segment would be located within 10 centimeters proximally. The study result benefits in predicting the location of ganglionic
segment pre-operation and during the operation.

Keywords: Hirschsprung disease, Transitional zone, Aganglionic segment