Coyle D, et al. - In this observational study, serial sections of pull-through specimens obtained from children with Hirschsprung's disease (n = 12) were examined for the neuronal networks using DAB+ immunohistochemistry for Protein Gene Product 9.5 in order to estimate the extent of the histological transition zone in patients with Hirschsprung's disease. As per findings, the transition zone can extend for up to 13 cm in children with rectosigmoid Hirschsprung's disease. Possibility of a longer transition zone is suggested in children with long-segment disease. Transition zone pull-through may minimize with extension of resection at a minimum 5 cm beyond the most distal ganglionic intra-operative biopsy and intra-operative histological examination of the proximal resection margin.