Circumferential distribution of ganglion cells in the transition zone of children with Hirschsprung disease

We prospectively studied the circumferential distribution of ganglion cells in the transition zone from a study population of 21 patients with Hirschs prung disease (HD) undergoing a pull-through procedure over a 26-month peri od. Twelve cases were satisfactory for examination, in that the transition zone was contained within a single surgical specimen and specimen distortio n was minimal. Ganglion cells in the submucosa were counted in all 12 cases . In seven of the cases, the transition zone was proximal to the rectal sle eve and myenteric plexus ganglion cells were also counted. We found an uneven circumferential distribution of ganglion cells in both m yenteric plexus and submucosa of: the transition zone, resulting in a "lead ing edge" of ganglion cells extending into aganglionic distal bowel. The ma ximum length of this leading edge was 2.4 cm and 2.1 cm in the myenteric pl exus and submucosa, respectively. Ganglion cells at the tip of the leading edge were present in clusters of up to six ganglion cells, in marked contra st to an absence of ganglion cells for most of the remainder of the circumf erence. Closely spaced myenteric plexus ganglia were seen at the tip of the leading edge in some cases. The leading edge was more frequently observed along the antimesenteric side, but this was not statistically significant. Our findings have relevance in the interpretation of intraoperative biopsie s at the time of pull-through surgery and subsequent biopsies of neorectum in patients with surgically corrected HD.