A case of nonrotation of the midgut with a middle mesenteric artery.

In 2002, we came across a very rare case of nonrotation of the midgut with a middle mesenteric artery (MM) (tentative name). It was found in a 73-year-old Japanese female cadaver donated for student dissection at Kumamoto University. In this case, the small intestine occupied the right half of the abdominal cavity and the large intestine occupied the left half. The caecum was situated on the anterior inferior part of the abdominal cavity near the midline. The duodenum (Du) was fused to the posterior abdominal wall. The small intestine except the Du and the ascending colon were suspended from the posterior abdominal wall by the mesentery, but the remainder of the colon was fused to the left posterior abdominal wall. In addition, an anomalous branch arose from the abdominal aorta between the superior and inferior mesenteric arteries (SM and IM) in this case. It chiefly supplied the ascending and the transverse colons and anastomosed with the SM and IM, respectively, through the marginal arteries. It is very rare that these anomalies appear simultaneously in one body. In this case, it is difficult to declare that the existence of the MM directly caused the nonrotation of the midgut, but it is reasonable to suppose some kind of relation between them.