Multimodality characterization of a noncommunicating congenital duodenal duplication cyst causing pyloric outflow obstruction in a young dog

A 10‐month‐old German Shepherd Dog presented for evaluation of intermittent vomiting. Abdominal radiographs revealed a marked right cranial mass effect. Initial differentials included abscess/cyst or less likely neoplasia from undetermined origin. On abdominal ultrasound the mass appeared cystic and thin walled. Computed tomography revealed a large cystic lesion originating from the pyloroduodenal junction causing pyloric outflow obstruction. A noncommunicating duodenal duplication cyst was found on exploratory laparotomy and further confirmed with histopathology and immunohistochemistry. Enteric duplication cyst should be considered as a differential in young dogs with gastrointestinal signs and a cystic abdominal mass detected with different imaging modalities.