On biodigital anatomy browser I found a structure called the mesocolon. I didn't find the term in Uberon and I'm unclear whether it's simply a synonym for mesenterium or whether it's a separate concept.
Mesentery is the name of a whole set of tissues attaching the intestines to the abdominal wall.
In human anatomy, there are three different portions of the mesentery:
- Mesenterium sensu strictu, also called Meso
- Mesocolon transversum
- Mesocolon sigmoideum, also called Mesosigmoideum
Two smaller mesenteries can be found at the appendix (Mesoappendix), and at the cranial part of the rectum (Mesorectum)
So... Mesocolon is a part of the mesentery, but no synonym.