During development, the bowel rotates 270° anticlockwise in two locations: the foregut and midgut junction (duodenum) and midgut-hindgut location (cecum), so that the ligament of Treitz is located left to the midline and cecum reaches the right iliac fossa. Completeness of rotation can be classified into four cathegories:
|Normal rotation||Normal appearance of the gut, cecum in the right iliac fossa and the ligament of Treitz left to the midline|
|Incomplete rotation||Incomplete rotation of the duodenum, the ligament of Treitz is absent or right to the midline, or incomplete rotation of the oral colon with formation of Ladd's bands.|
|Non-rotation||Rotation less than 90° with absent ligament of Treitz and fixation of the cecum.|
|Reverse rotation||Rotation in clockwise direction, extremely rare.|
Classically, malrotation is also classified according to embryonic stage, in which the process was interrupted:
|Type 1 (non-rotation)||Before 6th intrauterine week, when the midgut bulges into the yolk sac.|
|Type 2||Between the 6th and 10th intrauterine week, when the gut herniates into the umbilical cord. The large bowel remains relatively fixed, therefore malrotation at this stage involves small bowel only. It has three subtypes:
|Type 3||After 10th intrauterine week, when the midgut returns from the umbilical cord back to the abdominal cavity. During this stage, rotation of the duodenal loop is completed before the rotation of the large bowel. It has four subtypes:
1. Tytgat GNJ, Tytgat SHAJ. Grading and Staging in Gastroenterology.
2. Stringer BA, Babyn PS. Pediatric Gastrointestinal Imaging and Intervention.