At least once a year, a funny looking UGI study sparks the traditional discussion on rotational anomalies of the GI tract. And the fact that radiologists and surgeons don't necessarily agree on the terms used to describe different types of rotational anomalies doesn't help. Assuming radiologic findings reflect intra-operative findings (and this is assuming with a capital "A"), the following classification is helpful.
Rotational anomalies refers to situations where normal 270 degree counter-clockwise rotation and subsequent fixation of the bowel between the 5th to 10th week of gestation is not completed. Normal rotation results in a wide mesenteric base, which protects the bowel from volvulus (Fig 1. Red line). The most important implication of rotational anomalies is that they result in a spectrum of abnormal mesenteric base lengths, and subsequently variable risks for midgut volvulus. Based on the radiologic literature, the two main types of intestinal rotational anomalies are incomplete rotation and non-rotation.
In the case of incomplete rotation, the most common type, the proximal and distal midgut both rotate between 90 and 180 degrees. This places both the duodeno-jejunal junction (DJJ) and the cecum in close proximity to each other, and thus results in a narrow mesenteric base, prone to volvulus (Fig 2).
The second most common type of rotational anomaly is intestinal non-rotation. In this form, there is minimal rotation (<90 degrees) of both the proximal and distal midgut. This keeps the proximal mesenteric attachment (DJJ) and the distal attachment (cecum) far enough from each other that the risk of volvulus is much lower than that with incomplete rotation.
Although this is a useful classification, it is important to always keep in mind that radiologic findings do not necessarily always reflect true anatomy, and the potential for false positive and negative findings on UGI exist.
Shew S B. Surgical concerns in malrotation and midgut volvulus. Pediatric Radiology (2009); 39:S167-181
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