**5. Clinical presentation**

Prenatally, maternal polyhydramnios is often detected in 30–65% of cases [14]. Sonographic evidence of two fluid-filled structures (double bubble) in the foetal abdomen can be visualized in approximately 44% of cases of congenital duodenal obstruction. These findings are often detected in the last trimester. Interestingly, the antenatal diagnosis of congenital duodenal obstruction has been found to decrease both pre- and postoperative complications [15–18].

Postnatally, the clinical presentation depends on whether the obstruction is complete or incomplete. With complete obstruction, the newborn will present with persistent bilious vomiting in the majority of cases. In approximately 10% of the cases where the obstruction is preampullary, the newborn's emesis will be nonbilious [19]. Due to the proximal nature of the obstruction, the abdomen is usually not distended. However, gastric fullness may be appreciated on a clinical examination [20]. In cases of incomplete duodenal obstruction, e.g., stenosis, the child will often present later with repeated emesis, feeding intolerance, and possibly failure to thrive.
