Acquired mega-colon in children most commonly due to –
Megacolon

Megacolon is an abnormal dilatation of colon that is not caused by mechanical obstruction.
Two main types of megacolon are -


Congenital megacolon → Hirschsprung disease
Acquired megacolon


Poor bowel habit                             
Idiopathic             
Infections → Chaga's disease 
Medication Antipsychotic drugs
Psychological problems
Bad bowel habit
Chaga's disease
Hirschsprung's disease