Hirschprung’s disease is a disease of the enteric nervous system where there are no ganglion cells in the hind gut. Without theses nerve cells, babies are unable to pass stool, which can cause an intestinal obstruction. Current research in Hirschsprung’s uses the chick/quail chimera to track enteric nervous system formation. Only 50% of Hirschsprung cases have a known genetic cause.

Cloacal exstrophy is a rare disease (1 in every 250,000 births) where an abdominal defect exposes the bladder, intestines, and genitals outside the body. The organs are “split” like a book, so the inner walls are exposed, or “inside-out”. Current knowledge of the causes of cloacal exstrophy are limited, but chicks are being used for their windowed-ovo to test possible inducers of the disease. Chicks are good models to use for embryonic induction injections like these because the chick can be followed through development after injection. [Männer J1 2003]

Anorectal malformation is an umbrella term for any malformation of the anus, rectum, or cloaca. This can include imperforate anus, anorectal fistula, rectourethral fistula, rectrovaginal fistula. These fistulas are a result of lack of separation of cloaca into different tracts. Anorectal malformations are commonly studied in the chick using the quail chimera.

Tracheoesophageal fistula is a maintained connection between the trachea and the esophagus. This comes from lack of differentiation between the embryonic pharynx. This needs to be corrected surgically in order to avoid aspiration.

Choleodochal cysts are cystic dilations of the biliary tree. They are not studied in chick.