ABSTRACT
The main differential feature of the gastrointestinal (GI) tract in comparison with other organ systems is that its ultrasound appearance varies significantly during pregnancy and also, for some sites, in the course of the same ultrasound examination, due to the physiology of swallowing, stomach emptying, and intestinal peristalsis. It is therefore necessary to become acquainted with the whole range of anatomic correlates. It should also be underlined that the origin of a cystic or solid mass detected in the abdominal cavity can also be difficult to identify with certainty. For example, a cystic anechoic lesion can correspond to very different diagnoses according to its site and the relationships with the adjacent viscera: enteric duplication cyst, mesenteric cyst, choledochal cyst, double bubble in duodenal atresia, adrenal hemorrhage, renal cyst, or ovarian cyst. Finally, it should be underlined that, as far as obstructive GI lesions are concerned (duodenal atresia, esophageal atresia, ileal atresia, etc.), the dilatation of the tract proximal to the obstruction can become sonographically evident only in the 3rd trimester.
