“…The commonest and least severe defect is anal stenosis -the narrowing of the anal opening. More severe is the imperforate anus, which (Belloni et al, 2000, Hagan et al, 2000, Hall et al, 1980, Kohlhase et al, 1998, Martinez-Frias et al, 2001, Rittler et al, 1996, Ross et al, 1998. Animal models for various digestive system malformations have been developed to investigate their genetic and environmental basis.…”