Is there one or two characteristic "odd" or "unusual" symptom or clinical feature of Hirschsprung Disease?
One of the defining features of Hirschsprung disease is vomiting bile, which is a green substance that helps break down fats and is made in the gall bladder. The gall bladder is a small organ that stores bile after it has been made by the liver and before it is released into the intestines. Vomiting bile is a symptom of other diseases as well, so the doctor will ask about other symptoms to diagnose Hirschsprung disease. If you or your child are vomiting bile contact your physician.
"Hirschsprung’s Disease" National Organization for Rare Disorders. 2005. https://rarediseases.org/rare-diseases/hirschsprungs-disease/#standard-therapies
Wesson, David. "Congenital aganglionic megacolon (Hirschsprung disease)" UpToDate. May 2016. Web. 14 Jun. 2016. http://www.uptodate.com/contents/congenital-aganglionic-megacolon-hirschsprung-disease?source=search_result&search=Hirschsprung%E2%80%99s+Disease&selectedTitle=1~66