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DEVELOPMENTAL ANOMALIES

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Normal Development

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The stomach develops from the distal part of the embryonic foregut. The dorsal aspect of the primitive stomach grows faster than the ventral aspect, resulting in its asymmetric configuration. There is approximately 90° of clockwise rotation, such that the shorter ventral border moves to the right and the longer dorsal border (greater curvature) moves to the left. During this rotation, the cranial aspect of the developing stomach (the fundus) moves to the left and the caudal aspect (antrum) moves to the right and superiorly. The dorsal mesentery (dorsal mesogastrium) is carried to the left as the stomach rotates, thereby forming the boundary of the lesser sac of the peritoneum. The embryonic ventral mesentery attaches the stomach to the abdominal wall and liver. Alterations in this developmental sequence of gastric rotation and fixation cause the various forms of gastric malrotation.

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Volvulus and Malrotation

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Gastric malrotation refers to a spectrum of abnormalities in which 1 portion of the stomach is abnormally rotated around another. Deficient ligamentous fixation is the usual cause of rotational abnormalities of the stomach. There are 4 major anchoring ligaments of the stomach: the gastrohepatic, gastrophrenic, gastrosplenic, and gastrocolic ligaments. In addition, the distal portion of the stomach is relatively fixed by the retroperitoneal location of the duodenum. Rotational anomalies of the stomach are sometimes related to congenital malposition of the stomach (e.g., intrathoracic stomach) and/or congenital or acquired abnormalities of the diaphragm (e.g., congenital diaphragmatic hernia). There are rare reports of gastric volvulus in association with wandering spleen. In some instances of gastric malrotation, there is an acquired deficiency of gastric fixation due to prior surgery. About one-third of children with gastric volvulus have no known associated anomalies; this is termed primary or idiopathic volvulus.1–5

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Rotational abnormalities of the stomach are classified as organoaxial and mesenteroaxial. Organoaxial rotation occurs around a line joining the hiatus and the pylorus. Mesenteroaxial rotation occurs around a line joining the greater and lesser curvatures. With gastric herniation through the esophageal hiatus, anterior organoaxial rotation is common. Deviation of the greater curvature is in an anterior and cephalad direction; this can be likened to the effect of twisting the distal aspect of the stomach in a counterclockwise direction. Posterior organoaxial rotation is uncommon. Mesenteroaxial rotation occurs along an axis 90° to the longitudinal axis. The stomach is flipped ("upside-down stomach"), with the antrum moving anteriorly and superiorly, and the greater curvature remaining on the left. Occasionally, there is rotation about both the organoaxial and mesenteroaxial axes; this is a combined volvulus. The term gastric volvulus refers to strangulation and obstruction of a malrotated stomach. By some definitions, volvulus refers to rotation of at least 180°, while gastric torsion indicates rotation of < 180°.6,7

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Mesenteroaxial volvulus of the stomach sometimes presents as an abdominal catastrophe, because torsion of the stomach in this manner ...

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