ROSH Gastrointestinal Practice Exam

What is the most likely diagnosis for a 6-week-old boy with a history of progressive non-bilious vomiting?

1. Intussusception

2. Jejunal atresia

3. Midgut volvulus

4. Pyloric stenosis

The correct answer is: Pyloric stenosis

In a 6-week-old infant presenting with progressive non-bilious vomiting, the most likely diagnosis is pyloric stenosis. This condition occurs due to hypertrophy of the pyloric muscle, which impairs gastric emptying into the duodenum. As a result, infants experience projectile vomiting that is often described as non-bilious because the obstruction occurs before the bile duct junction in the duodenum. The age of the patient also supports this diagnosis, as pyloric stenosis typically presents between 3 to 12 weeks of life, with a peak incidence around 6 weeks. Additionally, infants with pyloric stenosis often show signs of dehydration and may be hungry soon after vomiting, indicating that they are not retaining any food. In contrast, although intussusception, jejunal atresia, and midgut volvulus can also cause vomiting in infants, they usually present with different clinical signs or age patterns. Intussusception might cause bilious vomiting and is less common at this age. Jejunal atresia often presents with either bile-stained vomiting or inability to pass meconium. Midgut volvulus typically occurs due to malrotation and is generally associated with severe abdominal pain and bilious vomiting.