Abstract
Background: Duplication cysts are rare congenital anomalies that can occur anywhere in the gastrointestinal tract from the mouth up to the anus. Acquired gastric outlet obstruction (GOO) during infancy beyond the neonatal period is a very rare condition and should be considered when other causes of GOO such as infantile hypertrophic pyloric stenosis, antral diaphragm, and pyloric atresia are excluded.Case Presentation: We report a one-year old female infant who presented with an acute onset of copious persistent vomiting that was initially diagnosed with a duplication cyst of the duodenum, but was found to have GOO after surgical exploration.Conclusion: Clinicians should be mindful of the common causes of GOO and have a high index of suspicion for acquired causes.