Katz et al. described nine findings for distinguishing normal and abnormal duodenal / jejunal positioning on upper gastrointestinal studies to detect subtle abnormalities indicative of midgut malrotation.

• One abnormality represents normal variation
• Two abnormalities represent indeterminate finding
• Three and more abnormalities found together indicate malrotation

Pylorus:

1) pylorus to left of the midline

Duodenojejunal flexure:

2) below level of L1-L2 intervertebral disk space in child under 18 years
3) >1.3 corrected distance below apex of the duodenal bulb
4) to right of the left pedicle

Segment between inferior and duodenojejunal flexures:

5) Intervening obstruction
6) Connecting line not longest side of triangle
7) Connecting line <2.6 (corrected distance)

Jejunum:

8) Corkscrewing or zigzagging beyond duodenojejunal flexure
9) To right of the spine
 

References:

1. Katz ME, Siegel MJ, Shackelford GD, McAlister WH. The position and mobility of the duodenum in children. AJR Am J Roentgenol 1987; 148: 947–951. http://www.ajronline.org/doi/pdf/10.2214/ajr.148.5.947