CT appearance of the duodenum and mesenteric vessels in children with normal and abnormal bowel rotation

Background Demonstration of the third duodenal segment (D3) in retroperitoneal location has been recently proposed as a method for excluding malrotation. Objective This study was performed to determine whether a retroperitoneal third duodenal segment can reliably exclude malrotation. Materials and methods CTs of 38 patients with proven malrotation and 100 patients without malrotation were evaluated for the location of the duodenum/proximal small bowel, and the relationship of the superior mesenteric vein (SMV) to superior mesenteric artery (SMA). Results The D3 segment was in normal retroperitoneal location in 100% of control patients, compared to 2.5% or (1 of 38) of patients with malrotation. Nine of 11 patients (91%) with malrotation imaged prior to surgery had the proximal bowel in an abnormal location, while all 100 control patients had it in a normal location. The SMV was in normal relationship to the SMA in 11/38 patients (29%) with malrotation, compared to 79% of normal controls. In 10 controls, a branch of the SMV was partially wrapped around the SMA, potentially mimicking partial mesenteric volvulus. Conclusion A retroperitoneal location of the D3 segment makes the diagnosis of malrotation unlikely but not impossible. Additional imaging of the duodenojejunal junction or cecum may be necessary to reliably exclude intestinal malrotation.