need help urgently

my 4yo daughter is severely constipated, she hasn't had a bowel movement in 10 days.
we took her to the doctor yesterday, and he prescribed mineral Oil Enema s, but here's the big problem. when we gave her one, she just expelled the enema, and was not able to have a bowel movement, instead it tried to come out, but there was a large bulge in the anal area , and she started crying very loudly. she quit trying and it went back inside. what should we do. I've talked to the doctor and he wants to do a manual disimpaction followed by a colonoscopy. and I would appreciate some advice.