Transverse part [Caudal part]

The transverse part of the duodenum (Pars transversa duodeni) begins after the caudal duodenal flexure and extends to the left, but its length and shape vary greatly.

It is longest in Humans and Equids, where it clearly crosses transversely over the ventral side of the caudal vena cava and the aorta to reach the left lumbar region. It is much shorter in Carnivores, where it forms a curve that connects seamlessly with the ascending part. In Ruminants, it is so short that it merges with the caudal flexure and loses its individuality. As a result, the third flexure of the duodenum (between transverse part and ascending part) is often difficult to identify and has not been named in these species.