Case 82 - Reversal of superior mesenteric artery and vein in midgut volvulus

Summary

Imaging description

The misalignment of the superior mesenteric artery (SMA)– superior mesenteric vein (SMV) complex and malpositioning of bowel structures may be seen in an adult asymptomatic patient. Normally the SMV is to the right of the SMA; with malrotation, the SMV may occupy a position directly anterior or to the left of the SMA creating a distinctive “whirlpool” pattern (Figures 82.1A and 82.1B). This can be identified on cross-sectional imaging. There is misplacement of the duo-denojejunal junction to the right of the midline with the presence of the jejunal loops in the right abdomen and a left-sided-colon (Figure 82.1C). Associated pancreatic abnormalities may also be present such as aplasia of the uncinate process and short pancreas (Figure 82.1D). Upper GI examination may also be performed to confirm the course of the duodenum and positioning of the ligament of Treitz (Figure 82.2).

Importance

Bowel malrotation occurs from shortening of the small bowel mesenteric root during embryologic development with less than 270º of counterclockwise rotation through the umbilicus between the fifth and tenth week of gestation. Midgut volvulus is a major complication and is the most common cause of bowel obstruction in adults with malrotation. However, bowel malrotation mostly presents as chronic abdominal pain in adults. The symptoms may be due to acute or chronic intestinal obstruction caused by the presence of abnormal peritoneal bands (Ladd's bands) or a volvulus. There is also a high association with peptic ulcer disease, which may be caused by chronic partial gastric or duodenal outlet obstruction.

Typical clinical scenario

Bowel malrotation is usually asymptomatic in adults and may present as vague chronic abdominal pain. When complicated with midgut volvulus, symptoms of abdominal pain, bilious vomiting, and bloody stools may occur. Definitive treatment based upon the severity of symptoms is the Ladd procedure, which includes mobilization of the right colon and the duodenum, division of Ladd's bands and adhesions around the SMA, and appendectomy.