 Introduction/Background Vomiting is common in infants, and in the majority of cases is benign. However, vomiting can be a sign of underlying pathology, which could be related to obstruction along the course of the gastrointestinal (GI) tract and may be secondary to infectious etiologies, neurologic diseases, mechanical, or metabolic causes [1,2]. This topic will be limited to the role of imaging in evaluation of complete or partial GI obstruction. Clinically, vomiting is categorized as being nonbilious or bilious; the latter suggests the point of obstruction is distal to the ampulla of Vater. Most commonly, nonbilious vomiting is actually regurgitation, known as gastroesophageal reflux (GER). The clinical differentiation between vomiting and regurgitation may be challenging. Vomiting, secondary to GER, is normal in infants, with decreased incidence with age and resolves in time. It usually has no definitive pathologic cause and is unrelated to a functional defect. Rarely, regurgitation may be due to displacement of a portion of the stomach into the chest (ie, hiatal hernia). In other cases, lower esophageal sphincter pressures or delays in gastric emptying have been implicated as causative and typically resolve in time [1]. Parental complaints of vomiting or regurgitation in infants are common. The cause is usually GER, particularly in the first weeks of life and in part because of overfeeding. Infants with normal weight gain and no other symptoms tend not to have obstruction as the cause of their vomiting [3]. Bilious emesis or repeated forceful vomiting should be evaluated for underlying obstruction. When evaluating a neonate who presents in the first week of life with vomiting, a congenital GI tract abnormality is a primary consideration.
Vomiting in Infants.  Introduction/Background Vomiting is common in infants, and in the majority of cases is benign. However, vomiting can be a sign of underlying pathology, which could be related to obstruction along the course of the gastrointestinal (GI) tract and may be secondary to infectious etiologies, neurologic diseases, mechanical, or metabolic causes [1,2]. This topic will be limited to the role of imaging in evaluation of complete or partial GI obstruction. Clinically, vomiting is categorized as being nonbilious or bilious; the latter suggests the point of obstruction is distal to the ampulla of Vater. Most commonly, nonbilious vomiting is actually regurgitation, known as gastroesophageal reflux (GER). The clinical differentiation between vomiting and regurgitation may be challenging. Vomiting, secondary to GER, is normal in infants, with decreased incidence with age and resolves in time. It usually has no definitive pathologic cause and is unrelated to a functional defect. Rarely, regurgitation may be due to displacement of a portion of the stomach into the chest (ie, hiatal hernia). In other cases, lower esophageal sphincter pressures or delays in gastric emptying have been implicated as causative and typically resolve in time [1]. Parental complaints of vomiting or regurgitation in infants are common. The cause is usually GER, particularly in the first weeks of life and in part because of overfeeding. Infants with normal weight gain and no other symptoms tend not to have obstruction as the cause of their vomiting [3]. Bilious emesis or repeated forceful vomiting should be evaluated for underlying obstruction. When evaluating a neonate who presents in the first week of life with vomiting, a congenital GI tract abnormality is a primary consideration.