Chapter 41: Intestinal Rotation Abnormalities

Key Points

Introduction

The embryology of intestinal rotation was described by Mall in 1898 and the potential surgical sequelae of anomalous intestinal rotation were described by Dott 25 years later. However, it was not until 1932 that Ladd first described 10 cases of malrotation and an operative technique for treating the condition. His account, expanded to include 21 cases by 1936, advocated the division of bands over the duodenum and placing the cecum in the left upper quadrant. Although to this day there remains some controversy regarding treatment or observation of variants of incomplete rotation, the optimal radiographic studies for diagnosis, the use of laparoscopy, and the treatment of asymptomatic rotational abnormalities in older children or children with heterotaxia syndromes (HS), the Ladd procedure remains the gold standard surgical procedure for children with intestinal malrotation who are at risk for midgut volvulus.

Embryology

For a child to be born with “normal” rotation, a precisely orchestrated sequence of events must occur during the fourth through 12th weeks of gestation. The molecular mechanisms controlling the initiation and progression of left–right asymmetry are the subjects of much investigation. Transient asymmetric expression of Nodal around Henson node in the gastrulating embryo appears to initiate left–right specification. Subsequent asymmetric expression of Pitx2 and Isl1(as a feedback loop) in the left side only of the dorsal mesentery and Tbx18 in the right side only appears to play a prominent role in promoting normal rotation through the differential induction of a tightly packed columnar epithelium on the left and cuboidal cells in more loosely packed mesenchymal elements on the right. This cellular architecture results in leftward “tilting” of the primitive gut tube. Misexpression of any of these elements in a murine model is associated with abnormal rotation. The macroscopic ramifications of these cellular events can be first appreciated during the fourth to fifth week postconception, when the straight tube of the primitive embryonic intestinal tract begins to elongate more rapidly than the embryo, causing it to “buckle” ventrally and force the duodenum, jejunum, ileum, ascending, and transverse colon to extend into the umbilical cord. The duodenum curves downward and to the right of the axis of the artery, initially completing a 90° counterclockwise turn. Over the next 3 weeks, the duodenum continues to rotate so that by the end of 8 weeks, it has undergone a 180° rotation. During the 10th gestational week, the intestines return precipitously back into the abdomen, led by the duodenum and jejunum and followed by the remainder of small bowel and then the colon in a left to right order. The cecum is the final portion of the intestine ...