Foregut duplication cyst: a novel computed tomography finding mimicking a small bowel hernia

RATIONALE A foregut duplication cyst (FDC) is an uncommon congenital disease. This report presents a case of mediastinal foregut duplication cyst that mimicked a diaphragmatic small bowel hernia. PATIENT CONCERN A 27-month-old girl was first referred for a mediastinal lesion found incidentally on a chest radiograph. At that time, our impression was cystic lung lesion such as congenital pulmonary airway malformation or pulmonary sequestration. At the age 6 years, she presented with recurrent vomiting. The physical examination and laboratory studies were within normal limits. DIAGNOSES Chest CT revealed a thin- and smooth-walled cystic mass containing an air-fluid level in the left paravertebral space. It had several inner circular folds and characteristic double-layer enhancement and inner circular fold. Our radiological impression was a type I congenital cystic adenomatoid malformation. INTERVENTIONS The patients undergone video-assisted thoracoscopic surgery for excision. The operative finding was the cystic mass with smooth bowel-like outer surface and located between the aorta and heart. The cyst was excised and confirmed to be a foregut duplication cyst pathologically. OUTCOMES The patient was doing well with no postoperative complications during follow-up. Recurrent vomiting was improved. This is the first case report describing foregut duplication cyst mimicking a small bowel hernia. LESSONS Foregut duplication cysts are rare congenital anomalies of primitive foregut origin. They can occur at any level of the alimentary track and comprise approximately 10% of all mediastinal tumors. Its characteristic double-layered histopathological nature, an FDC can show a double-layered enhancement pattern, which is typical in the alimentary tract.