Aganglionic megacolon HP:0002251 HP:0002030 HP:0004391 HP:0002606 Hirschsprung megacolon Aganglionic megacolon is characterized by congenital absence of intrinsic ganglion cells in the myenteric (Auerbach) and submucosal (Meissner) plexuses of the gastrointestinal tract. Enlarged colon lacking nerve cells An abnormality resulting from a lack of intestinal ganglion cells (i.e., an aganglionic section of bowel) that results in bowel obstruction with enlargement of the colon. Hirschsprung disease HP:0002029 Abnormal enteric ganglion morphology Megacolon