Higher magnification of the previous image showing hypertrophic submucosal nerve fibers and the absence of ganglion cells in submucosal (Meissner) plexus. Hirschsprung is subdivided anatomically into 4 types based on the length of the aganglionic segment. 1) Short segment: Involvement of rectum and distal sigmoid; about 75% to 80% of cases. 2) Long segment : Involvement extends upto hepatic flexure; about 15% of cases. 3) Total colonic aganglionosis (Zuezler-Wilson syndrome): Aganglionosis extends all the way to the cecum with some cases involving even the distal small bowel; 5% of cases. 4) Ultrashort segment: Involves only the distal rectum near the anal sphincter. It is a controversial entity.