Double bubble sign in children seen in A/E –
Obstruction of 2nd part of duodenum cause double bubble sign on plain abdominal radiograph. OIt may be due to -

i)  Annular pancreas
ii) Pancreatic pseudocyst
iii) Ladds band                         
iv) Tumor in the head of the pancrease
Ladds band
Annular pancreas
Pancreatic pseudocyst
Diaphragmatic hernia