Aganglionic segment is encountered in which pa of colon in case of Hirchsprung's disease ?

Ans is 'a' ie. 'Distal to the dilated segment' " The major feature of Hirschsprung ds is an absence of ganglion cells in the neural plexus of the intestinal wall, together with hyperophy of nerve trunks. The absence of ganglion cells gives rise to a contracted non-peristaltic segment with a dilated hyperophied segment of normal colon above it."- Bailey 24/e Similar loss of ganglion cells is seen in Achalasia of oesophagus. Achalasia is due to loss of ganglion cells in Myenteric or Auerbachs plexus. Achalasia differs from the hirschsprung ds of the colon in that the dilated esophagus contains no ganglion cells (or few cells) but the dilated colon contains normal ganglion cells.