= incomplete separation of foregut and notochord with persistence of canal of Kovalevski between yolk sac and notochord; cyst connected to meninges through midline defect

Frequency: rarest of bronchopulmonary foregut malformations (like pulmonary sequestration, bronchogenic cyst, enteric cyst)

Associated with: neurofibromatosis; meningocele; spinal malformation (stalk connects cyst and neural canal; usually no stalk between cyst and esophagus)

Location: anterior to spinal canal on mesenteric side of gut

• posterior mediastinal mass
• air-fluid level (if communicating with GI tract through diaphragmatic defect)
• spinal dysraphism at the same level:
  • midline cleft in centra (accommodates stalk)
  • anterior / posterior spina bifida
  • vertebral body anomalies: absent vertebra, butterfly vertebra, hemivertebra, scoliosis
  • diastematomyelia
  • thoracic myelomeningocele