In weeks 5-10 of pregnancy, the nerve cells from the brain gradually grow downward via the oesophagus, stomach, small intestine and large intestine. Sometimes these nerve cells do not reach the very last part of the intestine. This is the case with Hirschsprung's disease, named after the discoverer, the Danish paediatrician Harald Hirschsprung (1830-1916). Due to the absence of nerve cells, the intestine cannot work the stool outwards. The poop accumulates, causing the intestine to expand. Hirschsprung’s disease can sometimes occur in combination with, for example, Down's syndrome.