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Neonatal gastric outlet obstruction.

DISCUSSION Congenital gastric atresia is a rare cause of vomiting in early infancy, accounting for less than 1% of all congenital gastrointestinal (GI) tract obstructions. Gastric atresia is important to recognize because it can be misdiagnosed if clinical suspicion is low. The case in this study is unique because this neonate was initially worked up for pyloric stenosis with ultrasound (Fig. 1). The study result was negative, and he subsequently underwent an upper GI that showed total obstruction at the gastric outlet (Figs. 2 and 3). A second ultrasound was performed, which was diagnostic for congenital gastric atresia with a membranous diaphragm (Fig. 4). Congenital gastric atresia is usually limited to the gastric antrum or pylorus. There are 3 types of gastric atresia. The first type involves no connection between the lumen of the stomach and the duodenum. The second type involves a fibrous band connecting the stomach and the duodenum. The third type is the most common and involves a membranous diaphragm between the stomach and duodenum. This membrane is thought to be due to localized vascular occlusion during fetal life, rather than failure of recanalization. Hereditary link is poorly understood, however, this anomaly has been associated with epidermolysis bullosa. This association is thought to be due to inflammatory stricturing at the gastric antrum. Gastrointestinal atresias can also be associated with VACTERL, microgastria, and polysplenia/asplenia syndrome. Congenital gastric atresia usually presents as nonbilious vomiting and may present at birth or later in childhood depending on the size of the defect. Incomplete diaphragms present later because of the ability for some gastric contents to pass through the membrane. It has been proposed that some diaphragms may rupture spontaneously, making the diagnosis more prevalent than the literature would suggest. Thicker membranes require surgical resection to relieve the obstruction and are typically diagnosed in the first few days of life. A plain radiograph of a patient with gastric atresia shows a dilated stomach with paucity of distal bowel gas. An upper GI would then reveal complete obstruction at the gastric outlet. The ultrasound image in Figure 4 is diagnostic in that it demonstrates the membranous diaphragm. In Figure 3, note the band-like structure in the prepyloric region that extends across the stomach. This represents a hypoechoic submucosal layer covered by echogenic mucosa on either side. Sonographic findings typically show a distended stomach with a collapsed duodenum distal to the gastric outlet obstruction. The upper GI study in Figure 3 shows an enlarged stomach with total obstruction at the gastric antrum and no distal bowel gas. The upper GI study may also show a thin, linear filling defect in the gastric antrum. Further imaging would not be necessary for diagnosis in this case. The differential diagnosis for upper GI tract obstruction in the first few weeks of life is broad but can easily be narrowed once the level of obstruction is determined. Esophageal anomalies include esophageal atresia and tracheoesophageal fistula, where there is occlusion of the esophagus and/or tracts between the esophagus and the trachea. Esophageal duplications are less common and involve a cystic mass, which compresses the esophagus. Vascular rings can also cause compression of the esophagus, resulting in vomiting and failure to thrive. The primary modality for diagnosing esophageal anomalies is the esophagram.1