Hirschsprung's disease. Coloured barium X-ray of the abdomen of a child with Hirschsprung's disease. The colon (large intestine, orange) has become enlarged and is known as a megacolon. This is a congenital disease where nerves (ganglions) are absent from part of the colon. This prevents peristalsis (rhythmic muscle movements that propels faeces along the colon) and causes a bowel obstruction, which results in a build-up of faeces inside the colon, increasing its size. Treatment is with a surgical procedure known as a 'pull-through', where the functional portion of the colon is pulled towards the anus and sewn over the part lacking in nerve cells.