Newborn and infant babies with regurgitation :

Ultrasound is performed to exclude or confirm duodenal atresia and/or pyloric stenosis.

 

Duodenal atresia is a congenital complete closure or complete absence of a portion of the duodenum .

Signs detected include polyhydramnios (increased levels of amniotic fluid) during pregnancy  ultrasound, and intestinal obstruction in newborn babies

Pyloric Stenosis

A condition in which the pylorus muscles opening between the stomach and small intestine thickens, restricting passage of food from entering the small intestine. It occurs in babies under 6 months old, and more often in males.
Resultant features include forceful cramping and vomiting, dehydration, inability of baby to gain weight,  and even weight loss. Baby always  seems to be hungry.